imgact_elf: exclude invalid alignment requests

[FreeBSD/FreeBSD.git] / sys / kern / imgact_elf.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2017 Dell EMC
 * Copyright (c) 2000-2001, 2003 David O'Brien
 * Copyright (c) 1995-1996 Søren Schmidt
 * Copyright (c) 1996 Peter Wemm
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer
 *    in this position and unchanged.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_capsicum.h"

#include <sys/param.h>
#include <sys/capsicum.h>
#include <sys/compressor.h>
#include <sys/exec.h>
#include <sys/fcntl.h>
#include <sys/imgact.h>
#include <sys/imgact_elf.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/mman.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/procfs.h>
#include <sys/ptrace.h>
#include <sys/racct.h>
#include <sys/reg.h>
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <sys/sbuf.h>
#include <sys/sf_buf.h>
#include <sys/smp.h>
#include <sys/systm.h>
#include <sys/signalvar.h>
#include <sys/stat.h>
#include <sys/sx.h>
#include <sys/syscall.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/vnode.h>
#include <sys/syslog.h>
#include <sys/eventhandler.h>
#include <sys/user.h>

#include <vm/vm.h>
#include <vm/vm_kern.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_extern.h>

#include <machine/elf.h>
#include <machine/md_var.h>

#define ELF_NOTE_ROUNDSIZE      4
#define OLD_EI_BRAND    8

static int __elfN(check_header)(const Elf_Ehdr *hdr);
static Elf_Brandinfo *__elfN(get_brandinfo)(struct image_params *imgp,
    const char *interp, int32_t *osrel, uint32_t *fctl0);
static int __elfN(load_file)(struct proc *p, const char *file, u_long *addr,
    u_long *entry);
static int __elfN(load_section)(struct image_params *imgp, vm_ooffset_t offset,
    caddr_t vmaddr, size_t memsz, size_t filsz, vm_prot_t prot);
static int __CONCAT(exec_, __elfN(imgact))(struct image_params *imgp);
static bool __elfN(freebsd_trans_osrel)(const Elf_Note *note,
    int32_t *osrel);
static bool kfreebsd_trans_osrel(const Elf_Note *note, int32_t *osrel);
static bool __elfN(check_note)(struct image_params *imgp,
    Elf_Brandnote *checknote, int32_t *osrel, bool *has_fctl0,
    uint32_t *fctl0);
static vm_prot_t __elfN(trans_prot)(Elf_Word);
static Elf_Word __elfN(untrans_prot)(vm_prot_t);

SYSCTL_NODE(_kern, OID_AUTO, __CONCAT(elf, __ELF_WORD_SIZE),
    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "");

int __elfN(fallback_brand) = -1;
SYSCTL_INT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO,
    fallback_brand, CTLFLAG_RWTUN, &__elfN(fallback_brand), 0,
    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) " brand of last resort");

static int elf_legacy_coredump = 0;
SYSCTL_INT(_debug, OID_AUTO, __elfN(legacy_coredump), CTLFLAG_RW, 
    &elf_legacy_coredump, 0,
    "include all and only RW pages in core dumps");

int __elfN(nxstack) =
#if defined(__amd64__) || defined(__powerpc64__) /* both 64 and 32 bit */ || \
    (defined(__arm__) && __ARM_ARCH >= 7) || defined(__aarch64__) || \
    defined(__riscv)
        1;
#else
        0;
#endif
SYSCTL_INT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO,
    nxstack, CTLFLAG_RW, &__elfN(nxstack), 0,
    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) ": enable non-executable stack");

#if defined(__amd64__)
static int __elfN(vdso) = 1;
SYSCTL_INT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO,
    vdso, CTLFLAG_RWTUN, &__elfN(vdso), 0,
    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) ": enable vdso preloading");
#else
static int __elfN(vdso) = 0;
#endif

#if __ELF_WORD_SIZE == 32 && (defined(__amd64__) || defined(__i386__))
int i386_read_exec = 0;
SYSCTL_INT(_kern_elf32, OID_AUTO, read_exec, CTLFLAG_RW, &i386_read_exec, 0,
    "enable execution from readable segments");
#endif

static u_long __elfN(pie_base) = ET_DYN_LOAD_ADDR;
static int
sysctl_pie_base(SYSCTL_HANDLER_ARGS)
{
        u_long val;
        int error;

        val = __elfN(pie_base);
        error = sysctl_handle_long(oidp, &val, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        if ((val & PAGE_MASK) != 0)
                return (EINVAL);
        __elfN(pie_base) = val;
        return (0);
}
SYSCTL_PROC(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, pie_base,
    CTLTYPE_ULONG | CTLFLAG_MPSAFE | CTLFLAG_RW, NULL, 0,
    sysctl_pie_base, "LU",
    "PIE load base without randomization");

SYSCTL_NODE(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, aslr,
    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "");
#define ASLR_NODE_OID   __CONCAT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), _aslr)

/*
 * While for 64-bit machines ASLR works properly, there are
 * still some problems when using 32-bit architectures. For this
 * reason ASLR is only enabled by default when running native
 * 64-bit non-PIE executables.
 */
static int __elfN(aslr_enabled) = __ELF_WORD_SIZE == 64;
SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, enable, CTLFLAG_RWTUN,
    &__elfN(aslr_enabled), 0,
    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE))
    ": enable address map randomization");

/*
 * Enable ASLR only for 64-bit PIE binaries by default.
 */
static int __elfN(pie_aslr_enabled) = __ELF_WORD_SIZE == 64;
SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, pie_enable, CTLFLAG_RWTUN,
    &__elfN(pie_aslr_enabled), 0,
    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE))
    ": enable address map randomization for PIE binaries");

/*
 * Sbrk is now deprecated and it can be assumed, that in most
 * cases it will not be used anyway. This setting is valid only
 * for the ASLR enabled and allows for utilizing the bss grow region.
 */
static int __elfN(aslr_honor_sbrk) = 0;
SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, honor_sbrk, CTLFLAG_RW,
    &__elfN(aslr_honor_sbrk), 0,
    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) ": assume sbrk is used");

static int __elfN(aslr_stack_gap) = 3;
SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, stack_gap, CTLFLAG_RW,
    &__elfN(aslr_stack_gap), 0,
    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE))
    ": maximum percentage of main stack to waste on a random gap");

static int __elfN(sigfastblock) = 1;
SYSCTL_INT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, sigfastblock,
    CTLFLAG_RWTUN, &__elfN(sigfastblock), 0,
    "enable sigfastblock for new processes");

static bool __elfN(allow_wx) = true;
SYSCTL_BOOL(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, allow_wx,
    CTLFLAG_RWTUN, &__elfN(allow_wx), 0,
    "Allow pages to be mapped simultaneously writable and executable");

static Elf_Brandinfo *elf_brand_list[MAX_BRANDS];

#define aligned(a, t)   (rounddown2((u_long)(a), sizeof(t)) == (u_long)(a))

Elf_Brandnote __elfN(freebsd_brandnote) = {
        .hdr.n_namesz   = sizeof(FREEBSD_ABI_VENDOR),
        .hdr.n_descsz   = sizeof(int32_t),
        .hdr.n_type     = NT_FREEBSD_ABI_TAG,
        .vendor         = FREEBSD_ABI_VENDOR,
        .flags          = BN_TRANSLATE_OSREL,
        .trans_osrel    = __elfN(freebsd_trans_osrel)
};

static bool
__elfN(freebsd_trans_osrel)(const Elf_Note *note, int32_t *osrel)
{
        uintptr_t p;

        p = (uintptr_t)(note + 1);
        p += roundup2(note->n_namesz, ELF_NOTE_ROUNDSIZE);
        *osrel = *(const int32_t *)(p);

        return (true);
}

static const char GNU_ABI_VENDOR[] = "GNU";
static int GNU_KFREEBSD_ABI_DESC = 3;

Elf_Brandnote __elfN(kfreebsd_brandnote) = {
        .hdr.n_namesz   = sizeof(GNU_ABI_VENDOR),
        .hdr.n_descsz   = 16,   /* XXX at least 16 */
        .hdr.n_type     = 1,
        .vendor         = GNU_ABI_VENDOR,
        .flags          = BN_TRANSLATE_OSREL,
        .trans_osrel    = kfreebsd_trans_osrel
};

static bool
kfreebsd_trans_osrel(const Elf_Note *note, int32_t *osrel)
{
        const Elf32_Word *desc;
        uintptr_t p;

        p = (uintptr_t)(note + 1);
        p += roundup2(note->n_namesz, ELF_NOTE_ROUNDSIZE);

        desc = (const Elf32_Word *)p;
        if (desc[0] != GNU_KFREEBSD_ABI_DESC)
                return (false);

        /*
         * Debian GNU/kFreeBSD embed the earliest compatible kernel version
         * (__FreeBSD_version: <major><two digit minor>Rxx) in the LSB way.
         */
        *osrel = desc[1] * 100000 + desc[2] * 1000 + desc[3];

        return (true);
}

int
__elfN(insert_brand_entry)(Elf_Brandinfo *entry)
{
        int i;

        for (i = 0; i < MAX_BRANDS; i++) {
                if (elf_brand_list[i] == NULL) {
                        elf_brand_list[i] = entry;
                        break;
                }
        }
        if (i == MAX_BRANDS) {
                printf("WARNING: %s: could not insert brandinfo entry: %p\n",
                        __func__, entry);
                return (-1);
        }
        return (0);
}

int
__elfN(remove_brand_entry)(Elf_Brandinfo *entry)
{
        int i;

        for (i = 0; i < MAX_BRANDS; i++) {
                if (elf_brand_list[i] == entry) {
                        elf_brand_list[i] = NULL;
                        break;
                }
        }
        if (i == MAX_BRANDS)
                return (-1);
        return (0);
}

bool
__elfN(brand_inuse)(Elf_Brandinfo *entry)
{
        struct proc *p;
        bool rval = false;

        sx_slock(&allproc_lock);
        FOREACH_PROC_IN_SYSTEM(p) {
                if (p->p_sysent == entry->sysvec) {
                        rval = true;
                        break;
                }
        }
        sx_sunlock(&allproc_lock);

        return (rval);
}

static Elf_Brandinfo *
__elfN(get_brandinfo)(struct image_params *imgp, const char *interp,
    int32_t *osrel, uint32_t *fctl0)
{
        const Elf_Ehdr *hdr = (const Elf_Ehdr *)imgp->image_header;
        Elf_Brandinfo *bi, *bi_m;
        bool ret, has_fctl0;
        int i, interp_name_len;

        interp_name_len = interp != NULL ? strlen(interp) + 1 : 0;

        /*
         * We support four types of branding -- (1) the ELF EI_OSABI field
         * that SCO added to the ELF spec, (2) FreeBSD 3.x's traditional string
         * branding w/in the ELF header, (3) path of the `interp_path'
         * field, and (4) the ".note.ABI-tag" ELF section.
         */

        /* Look for an ".note.ABI-tag" ELF section */
        bi_m = NULL;
        for (i = 0; i < MAX_BRANDS; i++) {
                bi = elf_brand_list[i];
                if (bi == NULL)
                        continue;
                if (interp != NULL && (bi->flags & BI_BRAND_ONLY_STATIC) != 0)
                        continue;
                if (hdr->e_machine == bi->machine && (bi->flags &
                    (BI_BRAND_NOTE|BI_BRAND_NOTE_MANDATORY)) != 0) {
                        has_fctl0 = false;
                        *fctl0 = 0;
                        *osrel = 0;
                        ret = __elfN(check_note)(imgp, bi->brand_note, osrel,
                            &has_fctl0, fctl0);
                        /* Give brand a chance to veto check_note's guess */
                        if (ret && bi->header_supported) {
                                ret = bi->header_supported(imgp, osrel,
                                    has_fctl0 ? fctl0 : NULL);
                        }
                        /*
                         * If note checker claimed the binary, but the
                         * interpreter path in the image does not
                         * match default one for the brand, try to
                         * search for other brands with the same
                         * interpreter.  Either there is better brand
                         * with the right interpreter, or, failing
                         * this, we return first brand which accepted
                         * our note and, optionally, header.
                         */
                        if (ret && bi_m == NULL && interp != NULL &&
                            (bi->interp_path == NULL ||
                            (strlen(bi->interp_path) + 1 != interp_name_len ||
                            strncmp(interp, bi->interp_path, interp_name_len)
                            != 0))) {
                                bi_m = bi;
                                ret = 0;
                        }
                        if (ret)
                                return (bi);
                }
        }
        if (bi_m != NULL)
                return (bi_m);

        /* If the executable has a brand, search for it in the brand list. */
        for (i = 0; i < MAX_BRANDS; i++) {
                bi = elf_brand_list[i];
                if (bi == NULL || (bi->flags & BI_BRAND_NOTE_MANDATORY) != 0 ||
                    (interp != NULL && (bi->flags & BI_BRAND_ONLY_STATIC) != 0))
                        continue;
                if (hdr->e_machine == bi->machine &&
                    (hdr->e_ident[EI_OSABI] == bi->brand ||
                    (bi->compat_3_brand != NULL &&
                    strcmp((const char *)&hdr->e_ident[OLD_EI_BRAND],
                    bi->compat_3_brand) == 0))) {
                        /* Looks good, but give brand a chance to veto */
                        if (bi->header_supported == NULL ||
                            bi->header_supported(imgp, NULL, NULL)) {
                                /*
                                 * Again, prefer strictly matching
                                 * interpreter path.
                                 */
                                if (interp_name_len == 0 &&
                                    bi->interp_path == NULL)
                                        return (bi);
                                if (bi->interp_path != NULL &&
                                    strlen(bi->interp_path) + 1 ==
                                    interp_name_len && strncmp(interp,
                                    bi->interp_path, interp_name_len) == 0)
                                        return (bi);
                                if (bi_m == NULL)
                                        bi_m = bi;
                        }
                }
        }
        if (bi_m != NULL)
                return (bi_m);

        /* No known brand, see if the header is recognized by any brand */
        for (i = 0; i < MAX_BRANDS; i++) {
                bi = elf_brand_list[i];
                if (bi == NULL || bi->flags & BI_BRAND_NOTE_MANDATORY ||
                    bi->header_supported == NULL)
                        continue;
                if (hdr->e_machine == bi->machine) {
                        ret = bi->header_supported(imgp, NULL, NULL);
                        if (ret)
                                return (bi);
                }
        }

        /* Lacking a known brand, search for a recognized interpreter. */
        if (interp != NULL) {
                for (i = 0; i < MAX_BRANDS; i++) {
                        bi = elf_brand_list[i];
                        if (bi == NULL || (bi->flags &
                            (BI_BRAND_NOTE_MANDATORY | BI_BRAND_ONLY_STATIC))
                            != 0)
                                continue;
                        if (hdr->e_machine == bi->machine &&
                            bi->interp_path != NULL &&
                            /* ELF image p_filesz includes terminating zero */
                            strlen(bi->interp_path) + 1 == interp_name_len &&
                            strncmp(interp, bi->interp_path, interp_name_len)
                            == 0 && (bi->header_supported == NULL ||
                            bi->header_supported(imgp, NULL, NULL)))
                                return (bi);
                }
        }

        /* Lacking a recognized interpreter, try the default brand */
        for (i = 0; i < MAX_BRANDS; i++) {
                bi = elf_brand_list[i];
                if (bi == NULL || (bi->flags & BI_BRAND_NOTE_MANDATORY) != 0 ||
                    (interp != NULL && (bi->flags & BI_BRAND_ONLY_STATIC) != 0))
                        continue;
                if (hdr->e_machine == bi->machine &&
                    __elfN(fallback_brand) == bi->brand &&
                    (bi->header_supported == NULL ||
                    bi->header_supported(imgp, NULL, NULL)))
                        return (bi);
        }
        return (NULL);
}

static bool
__elfN(phdr_in_zero_page)(const Elf_Ehdr *hdr)
{
        return (hdr->e_phoff <= PAGE_SIZE &&
            (u_int)hdr->e_phentsize * hdr->e_phnum <= PAGE_SIZE - hdr->e_phoff);
}

static int
__elfN(check_header)(const Elf_Ehdr *hdr)
{
        Elf_Brandinfo *bi;
        int i;

        if (!IS_ELF(*hdr) ||
            hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
            hdr->e_ident[EI_DATA] != ELF_TARG_DATA ||
            hdr->e_ident[EI_VERSION] != EV_CURRENT ||
            hdr->e_phentsize != sizeof(Elf_Phdr) ||
            hdr->e_version != ELF_TARG_VER)
                return (ENOEXEC);

        /*
         * Make sure we have at least one brand for this machine.
         */

        for (i = 0; i < MAX_BRANDS; i++) {
                bi = elf_brand_list[i];
                if (bi != NULL && bi->machine == hdr->e_machine)
                        break;
        }
        if (i == MAX_BRANDS)
                return (ENOEXEC);

        return (0);
}

static int
__elfN(map_partial)(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
    vm_offset_t start, vm_offset_t end, vm_prot_t prot)
{
        struct sf_buf *sf;
        int error;
        vm_offset_t off;

        /*
         * Create the page if it doesn't exist yet. Ignore errors.
         */
        vm_map_fixed(map, NULL, 0, trunc_page(start), round_page(end) -
            trunc_page(start), VM_PROT_ALL, VM_PROT_ALL, MAP_CHECK_EXCL);

        /*
         * Find the page from the underlying object.
         */
        if (object != NULL) {
                sf = vm_imgact_map_page(object, offset);
                if (sf == NULL)
                        return (KERN_FAILURE);
                off = offset - trunc_page(offset);
                error = copyout((caddr_t)sf_buf_kva(sf) + off, (caddr_t)start,
                    end - start);
                vm_imgact_unmap_page(sf);
                if (error != 0)
                        return (KERN_FAILURE);
        }

        return (KERN_SUCCESS);
}

static int
__elfN(map_insert)(struct image_params *imgp, vm_map_t map, vm_object_t object,
    vm_ooffset_t offset, vm_offset_t start, vm_offset_t end, vm_prot_t prot,
    int cow)
{
        struct sf_buf *sf;
        vm_offset_t off;
        vm_size_t sz;
        int error, locked, rv;

        if (start != trunc_page(start)) {
                rv = __elfN(map_partial)(map, object, offset, start,
                    round_page(start), prot);
                if (rv != KERN_SUCCESS)
                        return (rv);
                offset += round_page(start) - start;
                start = round_page(start);
        }
        if (end != round_page(end)) {
                rv = __elfN(map_partial)(map, object, offset +
                    trunc_page(end) - start, trunc_page(end), end, prot);
                if (rv != KERN_SUCCESS)
                        return (rv);
                end = trunc_page(end);
        }
        if (start >= end)
                return (KERN_SUCCESS);
        if ((offset & PAGE_MASK) != 0) {
                /*
                 * The mapping is not page aligned.  This means that we have
                 * to copy the data.
                 */
                rv = vm_map_fixed(map, NULL, 0, start, end - start,
                    prot | VM_PROT_WRITE, VM_PROT_ALL, MAP_CHECK_EXCL);
                if (rv != KERN_SUCCESS)
                        return (rv);
                if (object == NULL)
                        return (KERN_SUCCESS);
                for (; start < end; start += sz) {
                        sf = vm_imgact_map_page(object, offset);
                        if (sf == NULL)
                                return (KERN_FAILURE);
                        off = offset - trunc_page(offset);
                        sz = end - start;
                        if (sz > PAGE_SIZE - off)
                                sz = PAGE_SIZE - off;
                        error = copyout((caddr_t)sf_buf_kva(sf) + off,
                            (caddr_t)start, sz);
                        vm_imgact_unmap_page(sf);
                        if (error != 0)
                                return (KERN_FAILURE);
                        offset += sz;
                }
        } else {
                vm_object_reference(object);
                rv = vm_map_fixed(map, object, offset, start, end - start,
                    prot, VM_PROT_ALL, cow | MAP_CHECK_EXCL |
                    (object != NULL ? MAP_VN_EXEC : 0));
                if (rv != KERN_SUCCESS) {
                        locked = VOP_ISLOCKED(imgp->vp);
                        VOP_UNLOCK(imgp->vp);
                        vm_object_deallocate(object);
                        vn_lock(imgp->vp, locked | LK_RETRY);
                        return (rv);
                } else if (object != NULL) {
                        MPASS(imgp->vp->v_object == object);
                        VOP_SET_TEXT_CHECKED(imgp->vp);
                }
        }
        return (KERN_SUCCESS);
}

static int
__elfN(load_section)(struct image_params *imgp, vm_ooffset_t offset,
    caddr_t vmaddr, size_t memsz, size_t filsz, vm_prot_t prot)
{
        struct sf_buf *sf;
        size_t map_len;
        vm_map_t map;
        vm_object_t object;
        vm_offset_t map_addr;
        int error, rv, cow;
        size_t copy_len;
        vm_ooffset_t file_addr;

        /*
         * It's necessary to fail if the filsz + offset taken from the
         * header is greater than the actual file pager object's size.
         * If we were to allow this, then the vm_map_find() below would
         * walk right off the end of the file object and into the ether.
         *
         * While I'm here, might as well check for something else that
         * is invalid: filsz cannot be greater than memsz.
         */
        if ((filsz != 0 && (off_t)filsz + offset > imgp->attr->va_size) ||
            filsz > memsz) {
                uprintf("elf_load_section: truncated ELF file\n");
                return (ENOEXEC);
        }

        object = imgp->object;
        map = &imgp->proc->p_vmspace->vm_map;
        map_addr = trunc_page((vm_offset_t)vmaddr);
        file_addr = trunc_page(offset);

        /*
         * We have two choices.  We can either clear the data in the last page
         * of an oversized mapping, or we can start the anon mapping a page
         * early and copy the initialized data into that first page.  We
         * choose the second.
         */
        if (filsz == 0)
                map_len = 0;
        else if (memsz > filsz)
                map_len = trunc_page(offset + filsz) - file_addr;
        else
                map_len = round_page(offset + filsz) - file_addr;

        if (map_len != 0) {
                /* cow flags: don't dump readonly sections in core */
                cow = MAP_COPY_ON_WRITE | MAP_PREFAULT |
                    (prot & VM_PROT_WRITE ? 0 : MAP_DISABLE_COREDUMP);

                rv = __elfN(map_insert)(imgp, map, object, file_addr,
                    map_addr, map_addr + map_len, prot, cow);
                if (rv != KERN_SUCCESS)
                        return (EINVAL);

                /* we can stop now if we've covered it all */
                if (memsz == filsz)
                        return (0);
        }

        /*
         * We have to get the remaining bit of the file into the first part
         * of the oversized map segment.  This is normally because the .data
         * segment in the file is extended to provide bss.  It's a neat idea
         * to try and save a page, but it's a pain in the behind to implement.
         */
        copy_len = filsz == 0 ? 0 : (offset + filsz) - trunc_page(offset +
            filsz);
        map_addr = trunc_page((vm_offset_t)vmaddr + filsz);
        map_len = round_page((vm_offset_t)vmaddr + memsz) - map_addr;

        /* This had damn well better be true! */
        if (map_len != 0) {
                rv = __elfN(map_insert)(imgp, map, NULL, 0, map_addr,
                    map_addr + map_len, prot, 0);
                if (rv != KERN_SUCCESS)
                        return (EINVAL);
        }

        if (copy_len != 0) {
                sf = vm_imgact_map_page(object, offset + filsz);
                if (sf == NULL)
                        return (EIO);

                /* send the page fragment to user space */
                error = copyout((caddr_t)sf_buf_kva(sf), (caddr_t)map_addr,
                    copy_len);
                vm_imgact_unmap_page(sf);
                if (error != 0)
                        return (error);
        }

        /*
         * Remove write access to the page if it was only granted by map_insert
         * to allow copyout.
         */
        if ((prot & VM_PROT_WRITE) == 0)
                vm_map_protect(map, trunc_page(map_addr), round_page(map_addr +
                    map_len), prot, 0, VM_MAP_PROTECT_SET_PROT);

        return (0);
}

static int
__elfN(load_sections)(struct image_params *imgp, const Elf_Ehdr *hdr,
    const Elf_Phdr *phdr, u_long rbase, u_long *base_addrp)
{
        vm_prot_t prot;
        u_long base_addr;
        bool first;
        int error, i;

        ASSERT_VOP_LOCKED(imgp->vp, __func__);

        base_addr = 0;
        first = true;

        for (i = 0; i < hdr->e_phnum; i++) {
                if (phdr[i].p_type != PT_LOAD || phdr[i].p_memsz == 0)
                        continue;

                /* Loadable segment */
                prot = __elfN(trans_prot)(phdr[i].p_flags);
                error = __elfN(load_section)(imgp, phdr[i].p_offset,
                    (caddr_t)(uintptr_t)phdr[i].p_vaddr + rbase,
                    phdr[i].p_memsz, phdr[i].p_filesz, prot);
                if (error != 0)
                        return (error);

                /*
                 * Establish the base address if this is the first segment.
                 */
                if (first) {
                        base_addr = trunc_page(phdr[i].p_vaddr + rbase);
                        first = false;
                }
        }

        if (base_addrp != NULL)
                *base_addrp = base_addr;

        return (0);
}

/*
 * Load the file "file" into memory.  It may be either a shared object
 * or an executable.
 *
 * The "addr" reference parameter is in/out.  On entry, it specifies
 * the address where a shared object should be loaded.  If the file is
 * an executable, this value is ignored.  On exit, "addr" specifies
 * where the file was actually loaded.
 *
 * The "entry" reference parameter is out only.  On exit, it specifies
 * the entry point for the loaded file.
 */
static int
__elfN(load_file)(struct proc *p, const char *file, u_long *addr,
        u_long *entry)
{
        struct {
                struct nameidata nd;
                struct vattr attr;
                struct image_params image_params;
        } *tempdata;
        const Elf_Ehdr *hdr = NULL;
        const Elf_Phdr *phdr = NULL;
        struct nameidata *nd;
        struct vattr *attr;
        struct image_params *imgp;
        u_long rbase;
        u_long base_addr = 0;
        int error;

#ifdef CAPABILITY_MODE
        /*
         * XXXJA: This check can go away once we are sufficiently confident
         * that the checks in namei() are correct.
         */
        if (IN_CAPABILITY_MODE(curthread))
                return (ECAPMODE);
#endif

        tempdata = malloc(sizeof(*tempdata), M_TEMP, M_WAITOK | M_ZERO);
        nd = &tempdata->nd;
        attr = &tempdata->attr;
        imgp = &tempdata->image_params;

        /*
         * Initialize part of the common data
         */
        imgp->proc = p;
        imgp->attr = attr;

        NDINIT(nd, LOOKUP, ISOPEN | FOLLOW | LOCKSHARED | LOCKLEAF,
            UIO_SYSSPACE, file);
        if ((error = namei(nd)) != 0) {
                nd->ni_vp = NULL;
                goto fail;
        }
        NDFREE(nd, NDF_ONLY_PNBUF);
        imgp->vp = nd->ni_vp;

        /*
         * Check permissions, modes, uid, etc on the file, and "open" it.
         */
        error = exec_check_permissions(imgp);
        if (error)
                goto fail;

        error = exec_map_first_page(imgp);
        if (error)
                goto fail;

        imgp->object = nd->ni_vp->v_object;

        hdr = (const Elf_Ehdr *)imgp->image_header;
        if ((error = __elfN(check_header)(hdr)) != 0)
                goto fail;
        if (hdr->e_type == ET_DYN)
                rbase = *addr;
        else if (hdr->e_type == ET_EXEC)
                rbase = 0;
        else {
                error = ENOEXEC;
                goto fail;
        }

        /* Only support headers that fit within first page for now      */
        if (!__elfN(phdr_in_zero_page)(hdr)) {
                error = ENOEXEC;
                goto fail;
        }

        phdr = (const Elf_Phdr *)(imgp->image_header + hdr->e_phoff);
        if (!aligned(phdr, Elf_Addr)) {
                error = ENOEXEC;
                goto fail;
        }

        error = __elfN(load_sections)(imgp, hdr, phdr, rbase, &base_addr);
        if (error != 0)
                goto fail;

        *addr = base_addr;
        *entry = (unsigned long)hdr->e_entry + rbase;

fail:
        if (imgp->firstpage)
                exec_unmap_first_page(imgp);

        if (nd->ni_vp) {
                if (imgp->textset)
                        VOP_UNSET_TEXT_CHECKED(nd->ni_vp);
                vput(nd->ni_vp);
        }
        free(tempdata, M_TEMP);

        return (error);
}

/*
 * Select randomized valid address in the map map, between minv and
 * maxv, with specified alignment.  The [minv, maxv) range must belong
 * to the map.  Note that function only allocates the address, it is
 * up to caller to clamp maxv in a way that the final allocation
 * length fit into the map.
 *
 * Result is returned in *resp, error code indicates that arguments
 * did not pass sanity checks for overflow and range correctness.
 */
static int
__CONCAT(rnd_, __elfN(base))(vm_map_t map, u_long minv, u_long maxv,
    u_int align, u_long *resp)
{
        u_long rbase, res;

        MPASS(vm_map_min(map) <= minv);

        if (minv >= maxv || minv + align >= maxv || maxv > vm_map_max(map)) {
                uprintf("Invalid ELF segments layout\n");
                return (ENOEXEC);
        }

        arc4rand(&rbase, sizeof(rbase), 0);
        res = roundup(minv, (u_long)align) + rbase % (maxv - minv);
        res &= ~((u_long)align - 1);
        if (res >= maxv)
                res -= align;

        KASSERT(res >= minv,
            ("res %#lx < minv %#lx, maxv %#lx rbase %#lx",
            res, minv, maxv, rbase));
        KASSERT(res < maxv,
            ("res %#lx > maxv %#lx, minv %#lx rbase %#lx",
            res, maxv, minv, rbase));

        *resp = res;
        return (0);
}

static int
__elfN(enforce_limits)(struct image_params *imgp, const Elf_Ehdr *hdr,
    const Elf_Phdr *phdr, u_long et_dyn_addr)
{
        struct vmspace *vmspace;
        const char *err_str;
        u_long text_size, data_size, total_size, text_addr, data_addr;
        u_long seg_size, seg_addr;
        int i;

        err_str = NULL;
        text_size = data_size = total_size = text_addr = data_addr = 0;

        for (i = 0; i < hdr->e_phnum; i++) {
                if (phdr[i].p_type != PT_LOAD || phdr[i].p_memsz == 0)
                        continue;

                seg_addr = trunc_page(phdr[i].p_vaddr + et_dyn_addr);
                seg_size = round_page(phdr[i].p_memsz +
                    phdr[i].p_vaddr + et_dyn_addr - seg_addr);

                /*
                 * Make the largest executable segment the official
                 * text segment and all others data.
                 *
                 * Note that obreak() assumes that data_addr + data_size == end
                 * of data load area, and the ELF file format expects segments
                 * to be sorted by address.  If multiple data segments exist,
                 * the last one will be used.
                 */

                if ((phdr[i].p_flags & PF_X) != 0 && text_size < seg_size) {
                        text_size = seg_size;
                        text_addr = seg_addr;
                } else {
                        data_size = seg_size;
                        data_addr = seg_addr;
                }
                total_size += seg_size;
        }

        if (data_addr == 0 && data_size == 0) {
                data_addr = text_addr;
                data_size = text_size;
        }

        /*
         * Check limits.  It should be safe to check the
         * limits after loading the segments since we do
         * not actually fault in all the segments pages.
         */
        PROC_LOCK(imgp->proc);
        if (data_size > lim_cur_proc(imgp->proc, RLIMIT_DATA))
                err_str = "Data segment size exceeds process limit";
        else if (text_size > maxtsiz)
                err_str = "Text segment size exceeds system limit";
        else if (total_size > lim_cur_proc(imgp->proc, RLIMIT_VMEM))
                err_str = "Total segment size exceeds process limit";
        else if (racct_set(imgp->proc, RACCT_DATA, data_size) != 0)
                err_str = "Data segment size exceeds resource limit";
        else if (racct_set(imgp->proc, RACCT_VMEM, total_size) != 0)
                err_str = "Total segment size exceeds resource limit";
        PROC_UNLOCK(imgp->proc);
        if (err_str != NULL) {
                uprintf("%s\n", err_str);
                return (ENOMEM);
        }

        vmspace = imgp->proc->p_vmspace;
        vmspace->vm_tsize = text_size >> PAGE_SHIFT;
        vmspace->vm_taddr = (caddr_t)(uintptr_t)text_addr;
        vmspace->vm_dsize = data_size >> PAGE_SHIFT;
        vmspace->vm_daddr = (caddr_t)(uintptr_t)data_addr;

        return (0);
}

static int
__elfN(get_interp)(struct image_params *imgp, const Elf_Phdr *phdr,
    char **interpp, bool *free_interpp)
{
        struct thread *td;
        char *interp;
        int error, interp_name_len;

        KASSERT(phdr->p_type == PT_INTERP,
            ("%s: p_type %u != PT_INTERP", __func__, phdr->p_type));
        ASSERT_VOP_LOCKED(imgp->vp, __func__);

        td = curthread;

        /* Path to interpreter */
        if (phdr->p_filesz < 2 || phdr->p_filesz > MAXPATHLEN) {
                uprintf("Invalid PT_INTERP\n");
                return (ENOEXEC);
        }

        interp_name_len = phdr->p_filesz;
        if (phdr->p_offset > PAGE_SIZE ||
            interp_name_len > PAGE_SIZE - phdr->p_offset) {
                /*
                 * The vnode lock might be needed by the pagedaemon to
                 * clean pages owned by the vnode.  Do not allow sleep
                 * waiting for memory with the vnode locked, instead
                 * try non-sleepable allocation first, and if it
                 * fails, go to the slow path were we drop the lock
                 * and do M_WAITOK.  A text reference prevents
                 * modifications to the vnode content.
                 */
                interp = malloc(interp_name_len + 1, M_TEMP, M_NOWAIT);
                if (interp == NULL) {
                        VOP_UNLOCK(imgp->vp);
                        interp = malloc(interp_name_len + 1, M_TEMP, M_WAITOK);
                        vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
                }

                error = vn_rdwr(UIO_READ, imgp->vp, interp,
                    interp_name_len, phdr->p_offset,
                    UIO_SYSSPACE, IO_NODELOCKED, td->td_ucred,
                    NOCRED, NULL, td);
                if (error != 0) {
                        free(interp, M_TEMP);
                        uprintf("i/o error PT_INTERP %d\n", error);
                        return (error);
                }
                interp[interp_name_len] = '\0';

                *interpp = interp;
                *free_interpp = true;
                return (0);
        }

        interp = __DECONST(char *, imgp->image_header) + phdr->p_offset;
        if (interp[interp_name_len - 1] != '\0') {
                uprintf("Invalid PT_INTERP\n");
                return (ENOEXEC);
        }

        *interpp = interp;
        *free_interpp = false;
        return (0);
}

static int
__elfN(load_interp)(struct image_params *imgp, const Elf_Brandinfo *brand_info,
    const char *interp, u_long *addr, u_long *entry)
{
        char *path;
        int error;

        if (brand_info->emul_path != NULL &&
            brand_info->emul_path[0] != '\0') {
                path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
                snprintf(path, MAXPATHLEN, "%s%s",
                    brand_info->emul_path, interp);
                error = __elfN(load_file)(imgp->proc, path, addr, entry);
                free(path, M_TEMP);
                if (error == 0)
                        return (0);
        }

        if (brand_info->interp_newpath != NULL &&
            (brand_info->interp_path == NULL ||
            strcmp(interp, brand_info->interp_path) == 0)) {
                error = __elfN(load_file)(imgp->proc,
                    brand_info->interp_newpath, addr, entry);
                if (error == 0)
                        return (0);
        }

        error = __elfN(load_file)(imgp->proc, interp, addr, entry);
        if (error == 0)
                return (0);

        uprintf("ELF interpreter %s not found, error %d\n", interp, error);
        return (error);
}

/*
 * Impossible et_dyn_addr initial value indicating that the real base
 * must be calculated later with some randomization applied.
 */
#define ET_DYN_ADDR_RAND        1

static int
__CONCAT(exec_, __elfN(imgact))(struct image_params *imgp)
{
        struct thread *td;
        const Elf_Ehdr *hdr;
        const Elf_Phdr *phdr;
        Elf_Auxargs *elf_auxargs;
        struct vmspace *vmspace;
        vm_map_t map;
        char *interp;
        Elf_Brandinfo *brand_info;
        struct sysentvec *sv;
        u_long addr, baddr, et_dyn_addr, entry, proghdr;
        u_long maxalign, maxsalign, mapsz, maxv, maxv1;
        uint32_t fctl0;
        int32_t osrel;
        bool free_interp;
        int error, i, n;

        hdr = (const Elf_Ehdr *)imgp->image_header;

        /*
         * Do we have a valid ELF header ?
         *
         * Only allow ET_EXEC & ET_DYN here, reject ET_DYN later
         * if particular brand doesn't support it.
         */
        if (__elfN(check_header)(hdr) != 0 ||
            (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN))
                return (-1);

        /*
         * From here on down, we return an errno, not -1, as we've
         * detected an ELF file.
         */

        if (!__elfN(phdr_in_zero_page)(hdr)) {
                uprintf("Program headers not in the first page\n");
                return (ENOEXEC);
        }
        phdr = (const Elf_Phdr *)(imgp->image_header + hdr->e_phoff); 
        if (!aligned(phdr, Elf_Addr)) {
                uprintf("Unaligned program headers\n");
                return (ENOEXEC);
        }

        n = error = 0;
        baddr = 0;
        osrel = 0;
        fctl0 = 0;
        entry = proghdr = 0;
        interp = NULL;
        free_interp = false;
        td = curthread;

        /*
         * Somewhat arbitrary, limit accepted max alignment for the
         * loadable segment to the max supported superpage size. Too
         * large alignment requests are not useful and are indicators
         * of corrupted or outright malicious binary.
         */
        maxalign = PAGE_SIZE;
        maxsalign = PAGE_SIZE * 1024;
        for (i = MAXPAGESIZES - 1; i > 0; i--) {
                if (pagesizes[i] > maxsalign)
                        maxsalign = pagesizes[i];
        }

        mapsz = 0;

        for (i = 0; i < hdr->e_phnum; i++) {
                switch (phdr[i].p_type) {
                case PT_LOAD:
                        if (n == 0)
                                baddr = phdr[i].p_vaddr;
                        if (phdr[i].p_align > maxsalign) {
                                uprintf("Invalid segment alignment\n");
                                error = ENOEXEC;
                                goto ret;
                        }
                        if (phdr[i].p_align > maxalign)
                                maxalign = phdr[i].p_align;
                        mapsz += phdr[i].p_memsz;
                        n++;

                        /*
                         * If this segment contains the program headers,
                         * remember their virtual address for the AT_PHDR
                         * aux entry. Static binaries don't usually include
                         * a PT_PHDR entry.
                         */
                        if (phdr[i].p_offset == 0 &&
                            hdr->e_phoff + hdr->e_phnum * hdr->e_phentsize <=
                            phdr[i].p_filesz)
                                proghdr = phdr[i].p_vaddr + hdr->e_phoff;
                        break;
                case PT_INTERP:
                        /* Path to interpreter */
                        if (interp != NULL) {
                                uprintf("Multiple PT_INTERP headers\n");
                                error = ENOEXEC;
                                goto ret;
                        }
                        error = __elfN(get_interp)(imgp, &phdr[i], &interp,
                            &free_interp);
                        if (error != 0)
                                goto ret;
                        break;
                case PT_GNU_STACK:
                        if (__elfN(nxstack))
                                imgp->stack_prot =
                                    __elfN(trans_prot)(phdr[i].p_flags);
                        imgp->stack_sz = phdr[i].p_memsz;
                        break;
                case PT_PHDR:   /* Program header table info */
                        proghdr = phdr[i].p_vaddr;
                        break;
                }
        }

        brand_info = __elfN(get_brandinfo)(imgp, interp, &osrel, &fctl0);
        if (brand_info == NULL) {
                uprintf("ELF binary type \"%u\" not known.\n",
                    hdr->e_ident[EI_OSABI]);
                error = ENOEXEC;
                goto ret;
        }
        sv = brand_info->sysvec;
        et_dyn_addr = 0;
        if (hdr->e_type == ET_DYN) {
                if ((brand_info->flags & BI_CAN_EXEC_DYN) == 0) {
                        uprintf("Cannot execute shared object\n");
                        error = ENOEXEC;
                        goto ret;
                }
                /*
                 * Honour the base load address from the dso if it is
                 * non-zero for some reason.
                 */
                if (baddr == 0) {
                        if ((sv->sv_flags & SV_ASLR) == 0 ||
                            (fctl0 & NT_FREEBSD_FCTL_ASLR_DISABLE) != 0)
                                et_dyn_addr = __elfN(pie_base);
                        else if ((__elfN(pie_aslr_enabled) &&
                            (imgp->proc->p_flag2 & P2_ASLR_DISABLE) == 0) ||
                            (imgp->proc->p_flag2 & P2_ASLR_ENABLE) != 0)
                                et_dyn_addr = ET_DYN_ADDR_RAND;
                        else
                                et_dyn_addr = __elfN(pie_base);
                }
        }

        /*
         * Avoid a possible deadlock if the current address space is destroyed
         * and that address space maps the locked vnode.  In the common case,
         * the locked vnode's v_usecount is decremented but remains greater
         * than zero.  Consequently, the vnode lock is not needed by vrele().
         * However, in cases where the vnode lock is external, such as nullfs,
         * v_usecount may become zero.
         *
         * The VV_TEXT flag prevents modifications to the executable while
         * the vnode is unlocked.
         */
        VOP_UNLOCK(imgp->vp);

        /*
         * Decide whether to enable randomization of user mappings.
         * First, reset user preferences for the setid binaries.
         * Then, account for the support of the randomization by the
         * ABI, by user preferences, and make special treatment for
         * PIE binaries.
         */
        if (imgp->credential_setid) {
                PROC_LOCK(imgp->proc);
                imgp->proc->p_flag2 &= ~(P2_ASLR_ENABLE | P2_ASLR_DISABLE |
                    P2_WXORX_DISABLE | P2_WXORX_ENABLE_EXEC);
                PROC_UNLOCK(imgp->proc);
        }
        if ((sv->sv_flags & SV_ASLR) == 0 ||
            (imgp->proc->p_flag2 & P2_ASLR_DISABLE) != 0 ||
            (fctl0 & NT_FREEBSD_FCTL_ASLR_DISABLE) != 0) {
                KASSERT(et_dyn_addr != ET_DYN_ADDR_RAND,
                    ("et_dyn_addr == RAND and !ASLR"));
        } else if ((imgp->proc->p_flag2 & P2_ASLR_ENABLE) != 0 ||
            (__elfN(aslr_enabled) && hdr->e_type == ET_EXEC) ||
            et_dyn_addr == ET_DYN_ADDR_RAND) {
                imgp->map_flags |= MAP_ASLR;
                /*
                 * If user does not care about sbrk, utilize the bss
                 * grow region for mappings as well.  We can select
                 * the base for the image anywere and still not suffer
                 * from the fragmentation.
                 */
                if (!__elfN(aslr_honor_sbrk) ||
                    (imgp->proc->p_flag2 & P2_ASLR_IGNSTART) != 0)
                        imgp->map_flags |= MAP_ASLR_IGNSTART;
        }

        if ((!__elfN(allow_wx) && (fctl0 & NT_FREEBSD_FCTL_WXNEEDED) == 0 &&
            (imgp->proc->p_flag2 & P2_WXORX_DISABLE) == 0) ||
            (imgp->proc->p_flag2 & P2_WXORX_ENABLE_EXEC) != 0)
                imgp->map_flags |= MAP_WXORX;

        error = exec_new_vmspace(imgp, sv);
        vmspace = imgp->proc->p_vmspace;
        map = &vmspace->vm_map;

        imgp->proc->p_sysent = sv;
        imgp->proc->p_elf_brandinfo = brand_info;

        maxv = vm_map_max(map) - lim_max(td, RLIMIT_STACK);
        if (error == 0 && et_dyn_addr == ET_DYN_ADDR_RAND) {
                KASSERT((map->flags & MAP_ASLR) != 0,
                    ("ET_DYN_ADDR_RAND but !MAP_ASLR"));
                error = __CONCAT(rnd_, __elfN(base))(map,
                    vm_map_min(map) + mapsz + lim_max(td, RLIMIT_DATA),
                    /* reserve half of the address space to interpreter */
                    maxv / 2, 1UL << flsl(maxalign), &et_dyn_addr);
        }

        vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
        if (error != 0)
                goto ret;

        error = __elfN(load_sections)(imgp, hdr, phdr, et_dyn_addr, NULL);
        if (error != 0)
                goto ret;

        error = __elfN(enforce_limits)(imgp, hdr, phdr, et_dyn_addr);
        if (error != 0)
                goto ret;

        entry = (u_long)hdr->e_entry + et_dyn_addr;

        /*
         * We load the dynamic linker where a userland call
         * to mmap(0, ...) would put it.  The rationale behind this
         * calculation is that it leaves room for the heap to grow to
         * its maximum allowed size.
         */
        addr = round_page((vm_offset_t)vmspace->vm_daddr + lim_max(td,
            RLIMIT_DATA));
        if ((map->flags & MAP_ASLR) != 0) {
                maxv1 = maxv / 2 + addr / 2;
                error = __CONCAT(rnd_, __elfN(base))(map, addr, maxv1,
                    (MAXPAGESIZES > 1 && pagesizes[1] != 0) ?
                    pagesizes[1] : pagesizes[0], &map->anon_loc);
                if (error != 0)
                        goto ret;
        } else {
                map->anon_loc = addr;
        }

        imgp->entry_addr = entry;

        if (interp != NULL) {
                VOP_UNLOCK(imgp->vp);
                if ((map->flags & MAP_ASLR) != 0) {
                        /* Assume that interpreter fits into 1/4 of AS */
                        maxv1 = maxv / 2 + addr / 2;
                        error = __CONCAT(rnd_, __elfN(base))(map, addr,
                            maxv1, PAGE_SIZE, &addr);
                }
                if (error == 0) {
                        error = __elfN(load_interp)(imgp, brand_info, interp,
                            &addr, &imgp->entry_addr);
                }
                vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
                if (error != 0)
                        goto ret;
        } else
                addr = et_dyn_addr;

        /*
         * Construct auxargs table (used by the copyout_auxargs routine)
         */
        elf_auxargs = malloc(sizeof(Elf_Auxargs), M_TEMP, M_NOWAIT);
        if (elf_auxargs == NULL) {
                VOP_UNLOCK(imgp->vp);
                elf_auxargs = malloc(sizeof(Elf_Auxargs), M_TEMP, M_WAITOK);
                vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
        }
        elf_auxargs->execfd = -1;
        elf_auxargs->phdr = proghdr + et_dyn_addr;
        elf_auxargs->phent = hdr->e_phentsize;
        elf_auxargs->phnum = hdr->e_phnum;
        elf_auxargs->pagesz = PAGE_SIZE;
        elf_auxargs->base = addr;
        elf_auxargs->flags = 0;
        elf_auxargs->entry = entry;
        elf_auxargs->hdr_eflags = hdr->e_flags;

        imgp->auxargs = elf_auxargs;
        imgp->interpreted = 0;
        imgp->reloc_base = addr;
        imgp->proc->p_osrel = osrel;
        imgp->proc->p_fctl0 = fctl0;
        imgp->proc->p_elf_flags = hdr->e_flags;

ret:
        ASSERT_VOP_LOCKED(imgp->vp, "skipped relock");
        if (free_interp)
                free(interp, M_TEMP);
        return (error);
}

#define elf_suword __CONCAT(suword, __ELF_WORD_SIZE)

int
__elfN(freebsd_copyout_auxargs)(struct image_params *imgp, uintptr_t base)
{
        Elf_Auxargs *args = (Elf_Auxargs *)imgp->auxargs;
        Elf_Auxinfo *argarray, *pos;
        int error;

        argarray = pos = malloc(AT_COUNT * sizeof(*pos), M_TEMP,
            M_WAITOK | M_ZERO);

        if (args->execfd != -1)
                AUXARGS_ENTRY(pos, AT_EXECFD, args->execfd);
        AUXARGS_ENTRY(pos, AT_PHDR, args->phdr);
        AUXARGS_ENTRY(pos, AT_PHENT, args->phent);
        AUXARGS_ENTRY(pos, AT_PHNUM, args->phnum);
        AUXARGS_ENTRY(pos, AT_PAGESZ, args->pagesz);
        AUXARGS_ENTRY(pos, AT_FLAGS, args->flags);
        AUXARGS_ENTRY(pos, AT_ENTRY, args->entry);
        AUXARGS_ENTRY(pos, AT_BASE, args->base);
        AUXARGS_ENTRY(pos, AT_EHDRFLAGS, args->hdr_eflags);
        if (imgp->execpathp != 0)
                AUXARGS_ENTRY_PTR(pos, AT_EXECPATH, imgp->execpathp);
        AUXARGS_ENTRY(pos, AT_OSRELDATE,
            imgp->proc->p_ucred->cr_prison->pr_osreldate);
        if (imgp->canary != 0) {
                AUXARGS_ENTRY_PTR(pos, AT_CANARY, imgp->canary);
                AUXARGS_ENTRY(pos, AT_CANARYLEN, imgp->canarylen);
        }
        AUXARGS_ENTRY(pos, AT_NCPUS, mp_ncpus);
        if (imgp->pagesizes != 0) {
                AUXARGS_ENTRY_PTR(pos, AT_PAGESIZES, imgp->pagesizes);
                AUXARGS_ENTRY(pos, AT_PAGESIZESLEN, imgp->pagesizeslen);
        }
        if (imgp->sysent->sv_timekeep_base != 0) {
                AUXARGS_ENTRY(pos, AT_TIMEKEEP,
                    imgp->sysent->sv_timekeep_base);
        }
        AUXARGS_ENTRY(pos, AT_STACKPROT, imgp->sysent->sv_shared_page_obj
            != NULL && imgp->stack_prot != 0 ? imgp->stack_prot :
            imgp->sysent->sv_stackprot);
        if (imgp->sysent->sv_hwcap != NULL)
                AUXARGS_ENTRY(pos, AT_HWCAP, *imgp->sysent->sv_hwcap);
        if (imgp->sysent->sv_hwcap2 != NULL)
                AUXARGS_ENTRY(pos, AT_HWCAP2, *imgp->sysent->sv_hwcap2);
        AUXARGS_ENTRY(pos, AT_BSDFLAGS, __elfN(sigfastblock) ?
            ELF_BSDF_SIGFASTBLK : 0);
        AUXARGS_ENTRY(pos, AT_ARGC, imgp->args->argc);
        AUXARGS_ENTRY_PTR(pos, AT_ARGV, imgp->argv);
        AUXARGS_ENTRY(pos, AT_ENVC, imgp->args->envc);
        AUXARGS_ENTRY_PTR(pos, AT_ENVV, imgp->envv);
        AUXARGS_ENTRY_PTR(pos, AT_PS_STRINGS, imgp->ps_strings);
        if (imgp->sysent->sv_fxrng_gen_base != 0)
                AUXARGS_ENTRY(pos, AT_FXRNG, imgp->sysent->sv_fxrng_gen_base);
        if (imgp->sysent->sv_vdso_base != 0 && __elfN(vdso) != 0)
                AUXARGS_ENTRY(pos, AT_KPRELOAD, imgp->sysent->sv_vdso_base);
        AUXARGS_ENTRY(pos, AT_NULL, 0);

        free(imgp->auxargs, M_TEMP);
        imgp->auxargs = NULL;
        KASSERT(pos - argarray <= AT_COUNT, ("Too many auxargs"));

        error = copyout(argarray, (void *)base, sizeof(*argarray) * AT_COUNT);
        free(argarray, M_TEMP);
        return (error);
}

int
__elfN(freebsd_fixup)(uintptr_t *stack_base, struct image_params *imgp)
{
        Elf_Addr *base;

        base = (Elf_Addr *)*stack_base;
        base--;
        if (elf_suword(base, imgp->args->argc) == -1)
                return (EFAULT);
        *stack_base = (uintptr_t)base;
        return (0);
}

/*
 * Code for generating ELF core dumps.
 */

typedef void (*segment_callback)(vm_map_entry_t, void *);

/* Closure for cb_put_phdr(). */
struct phdr_closure {
        Elf_Phdr *phdr;         /* Program header to fill in */
        Elf_Off offset;         /* Offset of segment in core file */
};

struct note_info {
        int             type;           /* Note type. */
        outfunc_t       outfunc;        /* Output function. */
        void            *outarg;        /* Argument for the output function. */
        size_t          outsize;        /* Output size. */
        TAILQ_ENTRY(note_info) link;    /* Link to the next note info. */
};

TAILQ_HEAD(note_info_list, note_info);

extern int compress_user_cores;
extern int compress_user_cores_level;

static void cb_put_phdr(vm_map_entry_t, void *);
static void cb_size_segment(vm_map_entry_t, void *);
static void each_dumpable_segment(struct thread *, segment_callback, void *,
    int);
static int __elfN(corehdr)(struct coredump_params *, int, void *, size_t,
    struct note_info_list *, size_t, int);
static void __elfN(putnote)(struct thread *td, struct note_info *, struct sbuf *);

static void __elfN(note_fpregset)(void *, struct sbuf *, size_t *);
static void __elfN(note_prpsinfo)(void *, struct sbuf *, size_t *);
static void __elfN(note_prstatus)(void *, struct sbuf *, size_t *);
static void __elfN(note_threadmd)(void *, struct sbuf *, size_t *);
static void __elfN(note_thrmisc)(void *, struct sbuf *, size_t *);
static void __elfN(note_ptlwpinfo)(void *, struct sbuf *, size_t *);
static void __elfN(note_procstat_auxv)(void *, struct sbuf *, size_t *);
static void __elfN(note_procstat_proc)(void *, struct sbuf *, size_t *);
static void __elfN(note_procstat_psstrings)(void *, struct sbuf *, size_t *);
static void note_procstat_files(void *, struct sbuf *, size_t *);
static void note_procstat_groups(void *, struct sbuf *, size_t *);
static void note_procstat_osrel(void *, struct sbuf *, size_t *);
static void note_procstat_rlimit(void *, struct sbuf *, size_t *);
static void note_procstat_umask(void *, struct sbuf *, size_t *);
static void note_procstat_vmmap(void *, struct sbuf *, size_t *);

static int
core_compressed_write(void *base, size_t len, off_t offset, void *arg)
{

        return (core_write((struct coredump_params *)arg, base, len, offset,
            UIO_SYSSPACE, NULL));
}

int
__elfN(coredump)(struct thread *td, struct vnode *vp, off_t limit, int flags)
{
        struct ucred *cred = td->td_ucred;
        int compm, error = 0;
        struct sseg_closure seginfo;
        struct note_info_list notelst;
        struct coredump_params params;
        struct note_info *ninfo;
        void *hdr, *tmpbuf;
        size_t hdrsize, notesz, coresize;

        hdr = NULL;
        tmpbuf = NULL;
        TAILQ_INIT(&notelst);

        /* Size the program segments. */
        __elfN(size_segments)(td, &seginfo, flags);

        /*
         * Collect info about the core file header area.
         */
        hdrsize = sizeof(Elf_Ehdr) + sizeof(Elf_Phdr) * (1 + seginfo.count);
        if (seginfo.count + 1 >= PN_XNUM)
                hdrsize += sizeof(Elf_Shdr);
        td->td_proc->p_sysent->sv_elf_core_prepare_notes(td, &notelst, &notesz);
        coresize = round_page(hdrsize + notesz) + seginfo.size;

        /* Set up core dump parameters. */
        params.offset = 0;
        params.active_cred = cred;
        params.file_cred = NOCRED;
        params.td = td;
        params.vp = vp;
        params.comp = NULL;

#ifdef RACCT
        if (racct_enable) {
                PROC_LOCK(td->td_proc);
                error = racct_add(td->td_proc, RACCT_CORE, coresize);
                PROC_UNLOCK(td->td_proc);
                if (error != 0) {
                        error = EFAULT;
                        goto done;
                }
        }
#endif
        if (coresize >= limit) {
                error = EFAULT;
                goto done;
        }

        /* Create a compression stream if necessary. */
        compm = compress_user_cores;
        if ((flags & (SVC_PT_COREDUMP | SVC_NOCOMPRESS)) == SVC_PT_COREDUMP &&
            compm == 0)
                compm = COMPRESS_GZIP;
        if (compm != 0) {
                params.comp = compressor_init(core_compressed_write,
                    compm, CORE_BUF_SIZE,
                    compress_user_cores_level, &params);
                if (params.comp == NULL) {
                        error = EFAULT;
                        goto done;
                }
                tmpbuf = malloc(CORE_BUF_SIZE, M_TEMP, M_WAITOK | M_ZERO);
        }

        /*
         * Allocate memory for building the header, fill it up,
         * and write it out following the notes.
         */
        hdr = malloc(hdrsize, M_TEMP, M_WAITOK);
        error = __elfN(corehdr)(&params, seginfo.count, hdr, hdrsize, &notelst,
            notesz, flags);

        /* Write the contents of all of the writable segments. */
        if (error == 0) {
                Elf_Phdr *php;
                off_t offset;
                int i;

                php = (Elf_Phdr *)((char *)hdr + sizeof(Elf_Ehdr)) + 1;
                offset = round_page(hdrsize + notesz);
                for (i = 0; i < seginfo.count; i++) {
                        error = core_output((char *)(uintptr_t)php->p_vaddr,
                            php->p_filesz, offset, &params, tmpbuf);
                        if (error != 0)
                                break;
                        offset += php->p_filesz;
                        php++;
                }
                if (error == 0 && params.comp != NULL)
                        error = compressor_flush(params.comp);
        }
        if (error) {
                log(LOG_WARNING,
                    "Failed to write core file for process %s (error %d)\n",
                    curproc->p_comm, error);
        }

done:
        free(tmpbuf, M_TEMP);
        if (params.comp != NULL)
                compressor_fini(params.comp);
        while ((ninfo = TAILQ_FIRST(&notelst)) != NULL) {
                TAILQ_REMOVE(&notelst, ninfo, link);
                free(ninfo, M_TEMP);
        }
        if (hdr != NULL)
                free(hdr, M_TEMP);

        return (error);
}

/*
 * A callback for each_dumpable_segment() to write out the segment's
 * program header entry.
 */
static void
cb_put_phdr(vm_map_entry_t entry, void *closure)
{
        struct phdr_closure *phc = (struct phdr_closure *)closure;
        Elf_Phdr *phdr = phc->phdr;

        phc->offset = round_page(phc->offset);

        phdr->p_type = PT_LOAD;
        phdr->p_offset = phc->offset;
        phdr->p_vaddr = entry->start;
        phdr->p_paddr = 0;
        phdr->p_filesz = phdr->p_memsz = entry->end - entry->start;
        phdr->p_align = PAGE_SIZE;
        phdr->p_flags = __elfN(untrans_prot)(entry->protection);

        phc->offset += phdr->p_filesz;
        phc->phdr++;
}

/*
 * A callback for each_dumpable_segment() to gather information about
 * the number of segments and their total size.
 */
static void
cb_size_segment(vm_map_entry_t entry, void *closure)
{
        struct sseg_closure *ssc = (struct sseg_closure *)closure;

        ssc->count++;
        ssc->size += entry->end - entry->start;
}

void
__elfN(size_segments)(struct thread *td, struct sseg_closure *seginfo,
    int flags)
{
        seginfo->count = 0;
        seginfo->size = 0;

        each_dumpable_segment(td, cb_size_segment, seginfo, flags);
}

/*
 * For each writable segment in the process's memory map, call the given
 * function with a pointer to the map entry and some arbitrary
 * caller-supplied data.
 */
static void
each_dumpable_segment(struct thread *td, segment_callback func, void *closure,
    int flags)
{
        struct proc *p = td->td_proc;
        vm_map_t map = &p->p_vmspace->vm_map;
        vm_map_entry_t entry;
        vm_object_t backing_object, object;
        bool ignore_entry;

        vm_map_lock_read(map);
        VM_MAP_ENTRY_FOREACH(entry, map) {
                /*
                 * Don't dump inaccessible mappings, deal with legacy
                 * coredump mode.
                 *
                 * Note that read-only segments related to the elf binary
                 * are marked MAP_ENTRY_NOCOREDUMP now so we no longer
                 * need to arbitrarily ignore such segments.
                 */
                if ((flags & SVC_ALL) == 0) {
                        if (elf_legacy_coredump) {
                                if ((entry->protection & VM_PROT_RW) !=
                                    VM_PROT_RW)
                                        continue;
                        } else {
                                if ((entry->protection & VM_PROT_ALL) == 0)
                                        continue;
                        }
                }

                /*
                 * Dont include memory segment in the coredump if
                 * MAP_NOCORE is set in mmap(2) or MADV_NOCORE in
                 * madvise(2).  Do not dump submaps (i.e. parts of the
                 * kernel map).
                 */
                if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
                        continue;
                if ((entry->eflags & MAP_ENTRY_NOCOREDUMP) != 0 &&
                    (flags & SVC_ALL) == 0)
                        continue;
                if ((object = entry->object.vm_object) == NULL)
                        continue;

                /* Ignore memory-mapped devices and such things. */
                VM_OBJECT_RLOCK(object);
                while ((backing_object = object->backing_object) != NULL) {
                        VM_OBJECT_RLOCK(backing_object);
                        VM_OBJECT_RUNLOCK(object);
                        object = backing_object;
                }
                ignore_entry = (object->flags & OBJ_FICTITIOUS) != 0;
                VM_OBJECT_RUNLOCK(object);
                if (ignore_entry)
                        continue;

                (*func)(entry, closure);
        }
        vm_map_unlock_read(map);
}

/*
 * Write the core file header to the file, including padding up to
 * the page boundary.
 */
static int
__elfN(corehdr)(struct coredump_params *p, int numsegs, void *hdr,
    size_t hdrsize, struct note_info_list *notelst, size_t notesz,
    int flags)
{
        struct note_info *ninfo;
        struct sbuf *sb;
        int error;

        /* Fill in the header. */
        bzero(hdr, hdrsize);
        __elfN(puthdr)(p->td, hdr, hdrsize, numsegs, notesz, flags);

        sb = sbuf_new(NULL, NULL, CORE_BUF_SIZE, SBUF_FIXEDLEN);
        sbuf_set_drain(sb, sbuf_drain_core_output, p);
        sbuf_start_section(sb, NULL);
        sbuf_bcat(sb, hdr, hdrsize);
        TAILQ_FOREACH(ninfo, notelst, link)
            __elfN(putnote)(p->td, ninfo, sb);
        /* Align up to a page boundary for the program segments. */
        sbuf_end_section(sb, -1, PAGE_SIZE, 0);
        error = sbuf_finish(sb);
        sbuf_delete(sb);

        return (error);
}

void
__elfN(prepare_notes)(struct thread *td, struct note_info_list *list,
    size_t *sizep)
{
        struct proc *p;
        struct thread *thr;
        size_t size;

        p = td->td_proc;
        size = 0;

        size += __elfN(register_note)(td, list, NT_PRPSINFO, __elfN(note_prpsinfo), p);

        /*
         * To have the debugger select the right thread (LWP) as the initial
         * thread, we dump the state of the thread passed to us in td first.
         * This is the thread that causes the core dump and thus likely to
         * be the right thread one wants to have selected in the debugger.
         */
        thr = td;
        while (thr != NULL) {
                size += __elfN(register_note)(td, list, NT_PRSTATUS,
                    __elfN(note_prstatus), thr);
                size += __elfN(register_note)(td, list, NT_FPREGSET,
                    __elfN(note_fpregset), thr);
                size += __elfN(register_note)(td, list, NT_THRMISC,
                    __elfN(note_thrmisc), thr);
                size += __elfN(register_note)(td, list, NT_PTLWPINFO,
                    __elfN(note_ptlwpinfo), thr);
                size += __elfN(register_note)(td, list, -1,
                    __elfN(note_threadmd), thr);

                thr = thr == td ? TAILQ_FIRST(&p->p_threads) :
                    TAILQ_NEXT(thr, td_plist);
                if (thr == td)
                        thr = TAILQ_NEXT(thr, td_plist);
        }

        size += __elfN(register_note)(td, list, NT_PROCSTAT_PROC,
            __elfN(note_procstat_proc), p);
        size += __elfN(register_note)(td, list, NT_PROCSTAT_FILES,
            note_procstat_files, p);
        size += __elfN(register_note)(td, list, NT_PROCSTAT_VMMAP,
            note_procstat_vmmap, p);
        size += __elfN(register_note)(td, list, NT_PROCSTAT_GROUPS,
            note_procstat_groups, p);
        size += __elfN(register_note)(td, list, NT_PROCSTAT_UMASK,
            note_procstat_umask, p);
        size += __elfN(register_note)(td, list, NT_PROCSTAT_RLIMIT,
            note_procstat_rlimit, p);
        size += __elfN(register_note)(td, list, NT_PROCSTAT_OSREL,
            note_procstat_osrel, p);
        size += __elfN(register_note)(td, list, NT_PROCSTAT_PSSTRINGS,
            __elfN(note_procstat_psstrings), p);
        size += __elfN(register_note)(td, list, NT_PROCSTAT_AUXV,
            __elfN(note_procstat_auxv), p);

        *sizep = size;
}

void
__elfN(puthdr)(struct thread *td, void *hdr, size_t hdrsize, int numsegs,
    size_t notesz, int flags)
{
        Elf_Ehdr *ehdr;
        Elf_Phdr *phdr;
        Elf_Shdr *shdr;
        struct phdr_closure phc;
        Elf_Brandinfo *bi;

        ehdr = (Elf_Ehdr *)hdr;
        bi = td->td_proc->p_elf_brandinfo;

        ehdr->e_ident[EI_MAG0] = ELFMAG0;
        ehdr->e_ident[EI_MAG1] = ELFMAG1;
        ehdr->e_ident[EI_MAG2] = ELFMAG2;
        ehdr->e_ident[EI_MAG3] = ELFMAG3;
        ehdr->e_ident[EI_CLASS] = ELF_CLASS;
        ehdr->e_ident[EI_DATA] = ELF_DATA;
        ehdr->e_ident[EI_VERSION] = EV_CURRENT;
        ehdr->e_ident[EI_OSABI] = td->td_proc->p_sysent->sv_elf_core_osabi;
        ehdr->e_ident[EI_ABIVERSION] = 0;
        ehdr->e_ident[EI_PAD] = 0;
        ehdr->e_type = ET_CORE;
        ehdr->e_machine = bi->machine;
        ehdr->e_version = EV_CURRENT;
        ehdr->e_entry = 0;
        ehdr->e_phoff = sizeof(Elf_Ehdr);
        ehdr->e_flags = td->td_proc->p_elf_flags;
        ehdr->e_ehsize = sizeof(Elf_Ehdr);
        ehdr->e_phentsize = sizeof(Elf_Phdr);
        ehdr->e_shentsize = sizeof(Elf_Shdr);
        ehdr->e_shstrndx = SHN_UNDEF;
        if (numsegs + 1 < PN_XNUM) {
                ehdr->e_phnum = numsegs + 1;
                ehdr->e_shnum = 0;
        } else {
                ehdr->e_phnum = PN_XNUM;
                ehdr->e_shnum = 1;

                ehdr->e_shoff = ehdr->e_phoff +
                    (numsegs + 1) * ehdr->e_phentsize;
                KASSERT(ehdr->e_shoff == hdrsize - sizeof(Elf_Shdr),
                    ("e_shoff: %zu, hdrsize - shdr: %zu",
                     (size_t)ehdr->e_shoff, hdrsize - sizeof(Elf_Shdr)));

                shdr = (Elf_Shdr *)((char *)hdr + ehdr->e_shoff);
                memset(shdr, 0, sizeof(*shdr));
                /*
                 * A special first section is used to hold large segment and
                 * section counts.  This was proposed by Sun Microsystems in
                 * Solaris and has been adopted by Linux; the standard ELF
                 * tools are already familiar with the technique.
                 *
                 * See table 7-7 of the Solaris "Linker and Libraries Guide"
                 * (or 12-7 depending on the version of the document) for more
                 * details.
                 */
                shdr->sh_type = SHT_NULL;
                shdr->sh_size = ehdr->e_shnum;
                shdr->sh_link = ehdr->e_shstrndx;
                shdr->sh_info = numsegs + 1;
        }

        /*
         * Fill in the program header entries.
         */
        phdr = (Elf_Phdr *)((char *)hdr + ehdr->e_phoff);

        /* The note segement. */
        phdr->p_type = PT_NOTE;
        phdr->p_offset = hdrsize;
        phdr->p_vaddr = 0;
        phdr->p_paddr = 0;
        phdr->p_filesz = notesz;
        phdr->p_memsz = 0;
        phdr->p_flags = PF_R;
        phdr->p_align = ELF_NOTE_ROUNDSIZE;
        phdr++;

        /* All the writable segments from the program. */
        phc.phdr = phdr;
        phc.offset = round_page(hdrsize + notesz);
        each_dumpable_segment(td, cb_put_phdr, &phc, flags);
}

size_t
__elfN(register_note)(struct thread *td, struct note_info_list *list,
    int type, outfunc_t out, void *arg)
{
        const struct sysentvec *sv;
        struct note_info *ninfo;
        size_t size, notesize;

        sv = td->td_proc->p_sysent;
        size = 0;
        out(arg, NULL, &size);
        ninfo = malloc(sizeof(*ninfo), M_TEMP, M_ZERO | M_WAITOK);
        ninfo->type = type;
        ninfo->outfunc = out;
        ninfo->outarg = arg;
        ninfo->outsize = size;
        TAILQ_INSERT_TAIL(list, ninfo, link);

        if (type == -1)
                return (size);

        notesize = sizeof(Elf_Note) +           /* note header */
            roundup2(strlen(sv->sv_elf_core_abi_vendor) + 1, ELF_NOTE_ROUNDSIZE) +
                                                /* note name */
            roundup2(size, ELF_NOTE_ROUNDSIZE); /* note description */

        return (notesize);
}

static size_t
append_note_data(const void *src, void *dst, size_t len)
{
        size_t padded_len;

        padded_len = roundup2(len, ELF_NOTE_ROUNDSIZE);
        if (dst != NULL) {
                bcopy(src, dst, len);
                bzero((char *)dst + len, padded_len - len);
        }
        return (padded_len);
}

size_t
__elfN(populate_note)(int type, void *src, void *dst, size_t size, void **descp)
{
        Elf_Note *note;
        char *buf;
        size_t notesize;

        buf = dst;
        if (buf != NULL) {
                note = (Elf_Note *)buf;
                note->n_namesz = sizeof(FREEBSD_ABI_VENDOR);
                note->n_descsz = size;
                note->n_type = type;
                buf += sizeof(*note);
                buf += append_note_data(FREEBSD_ABI_VENDOR, buf,
                    sizeof(FREEBSD_ABI_VENDOR));
                append_note_data(src, buf, size);
                if (descp != NULL)
                        *descp = buf;
        }

        notesize = sizeof(Elf_Note) +           /* note header */
            roundup2(sizeof(FREEBSD_ABI_VENDOR), ELF_NOTE_ROUNDSIZE) +
                                                /* note name */
            roundup2(size, ELF_NOTE_ROUNDSIZE); /* note description */

        return (notesize);
}

static void
__elfN(putnote)(struct thread *td, struct note_info *ninfo, struct sbuf *sb)
{
        Elf_Note note;
        const struct sysentvec *sv;
        ssize_t old_len, sect_len;
        size_t new_len, descsz, i;

        if (ninfo->type == -1) {
                ninfo->outfunc(ninfo->outarg, sb, &ninfo->outsize);
                return;
        }

        sv = td->td_proc->p_sysent;

        note.n_namesz = strlen(sv->sv_elf_core_abi_vendor) + 1;
        note.n_descsz = ninfo->outsize;
        note.n_type = ninfo->type;

        sbuf_bcat(sb, &note, sizeof(note));
        sbuf_start_section(sb, &old_len);
        sbuf_bcat(sb, sv->sv_elf_core_abi_vendor,
            strlen(sv->sv_elf_core_abi_vendor) + 1);
        sbuf_end_section(sb, old_len, ELF_NOTE_ROUNDSIZE, 0);
        if (note.n_descsz == 0)
                return;
        sbuf_start_section(sb, &old_len);
        ninfo->outfunc(ninfo->outarg, sb, &ninfo->outsize);
        sect_len = sbuf_end_section(sb, old_len, ELF_NOTE_ROUNDSIZE, 0);
        if (sect_len < 0)
                return;

        new_len = (size_t)sect_len;
        descsz = roundup(note.n_descsz, ELF_NOTE_ROUNDSIZE);
        if (new_len < descsz) {
                /*
                 * It is expected that individual note emitters will correctly
                 * predict their expected output size and fill up to that size
                 * themselves, padding in a format-specific way if needed.
                 * However, in case they don't, just do it here with zeros.
                 */
                for (i = 0; i < descsz - new_len; i++)
                        sbuf_putc(sb, 0);
        } else if (new_len > descsz) {
                /*
                 * We can't always truncate sb -- we may have drained some
                 * of it already.
                 */
                KASSERT(new_len == descsz, ("%s: Note type %u changed as we "
                    "read it (%zu > %zu).  Since it is longer than "
                    "expected, this coredump's notes are corrupt.  THIS "
                    "IS A BUG in the note_procstat routine for type %u.\n",
                    __func__, (unsigned)note.n_type, new_len, descsz,
                    (unsigned)note.n_type));
        }
}

/*
 * Miscellaneous note out functions.
 */

#if defined(COMPAT_FREEBSD32) && __ELF_WORD_SIZE == 32
#include <compat/freebsd32/freebsd32.h>
#include <compat/freebsd32/freebsd32_signal.h>

typedef struct prstatus32 elf_prstatus_t;
typedef struct prpsinfo32 elf_prpsinfo_t;
typedef struct fpreg32 elf_prfpregset_t;
typedef struct fpreg32 elf_fpregset_t;
typedef struct reg32 elf_gregset_t;
typedef struct thrmisc32 elf_thrmisc_t;
#define ELF_KERN_PROC_MASK      KERN_PROC_MASK32
typedef struct kinfo_proc32 elf_kinfo_proc_t;
typedef uint32_t elf_ps_strings_t;
#else
typedef prstatus_t elf_prstatus_t;
typedef prpsinfo_t elf_prpsinfo_t;
typedef prfpregset_t elf_prfpregset_t;
typedef prfpregset_t elf_fpregset_t;
typedef gregset_t elf_gregset_t;
typedef thrmisc_t elf_thrmisc_t;
#define ELF_KERN_PROC_MASK      0
typedef struct kinfo_proc elf_kinfo_proc_t;
typedef vm_offset_t elf_ps_strings_t;
#endif

static void
__elfN(note_prpsinfo)(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct sbuf sbarg;
        size_t len;
        char *cp, *end;
        struct proc *p;
        elf_prpsinfo_t *psinfo;
        int error;

        p = arg;
        if (sb != NULL) {
                KASSERT(*sizep == sizeof(*psinfo), ("invalid size"));
                psinfo = malloc(sizeof(*psinfo), M_TEMP, M_ZERO | M_WAITOK);
                psinfo->pr_version = PRPSINFO_VERSION;
                psinfo->pr_psinfosz = sizeof(elf_prpsinfo_t);
                strlcpy(psinfo->pr_fname, p->p_comm, sizeof(psinfo->pr_fname));
                PROC_LOCK(p);
                if (p->p_args != NULL) {
                        len = sizeof(psinfo->pr_psargs) - 1;
                        if (len > p->p_args->ar_length)
                                len = p->p_args->ar_length;
                        memcpy(psinfo->pr_psargs, p->p_args->ar_args, len);
                        PROC_UNLOCK(p);
                        error = 0;
                } else {
                        _PHOLD(p);
                        PROC_UNLOCK(p);
                        sbuf_new(&sbarg, psinfo->pr_psargs,
                            sizeof(psinfo->pr_psargs), SBUF_FIXEDLEN);
                        error = proc_getargv(curthread, p, &sbarg);
                        PRELE(p);
                        if (sbuf_finish(&sbarg) == 0)
                                len = sbuf_len(&sbarg) - 1;
                        else
                                len = sizeof(psinfo->pr_psargs) - 1;
                        sbuf_delete(&sbarg);
                }
                if (error || len == 0)
                        strlcpy(psinfo->pr_psargs, p->p_comm,
                            sizeof(psinfo->pr_psargs));
                else {
                        KASSERT(len < sizeof(psinfo->pr_psargs),
                            ("len is too long: %zu vs %zu", len,
                            sizeof(psinfo->pr_psargs)));
                        cp = psinfo->pr_psargs;
                        end = cp + len - 1;
                        for (;;) {
                                cp = memchr(cp, '\0', end - cp);
                                if (cp == NULL)
                                        break;
                                *cp = ' ';
                        }
                }
                psinfo->pr_pid = p->p_pid;
                sbuf_bcat(sb, psinfo, sizeof(*psinfo));
                free(psinfo, M_TEMP);
        }
        *sizep = sizeof(*psinfo);
}

static void
__elfN(note_prstatus)(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct thread *td;
        elf_prstatus_t *status;

        td = arg;
        if (sb != NULL) {
                KASSERT(*sizep == sizeof(*status), ("invalid size"));
                status = malloc(sizeof(*status), M_TEMP, M_ZERO | M_WAITOK);
                status->pr_version = PRSTATUS_VERSION;
                status->pr_statussz = sizeof(elf_prstatus_t);
                status->pr_gregsetsz = sizeof(elf_gregset_t);
                status->pr_fpregsetsz = sizeof(elf_fpregset_t);
                status->pr_osreldate = osreldate;
                status->pr_cursig = td->td_proc->p_sig;
                status->pr_pid = td->td_tid;
#if defined(COMPAT_FREEBSD32) && __ELF_WORD_SIZE == 32
                fill_regs32(td, &status->pr_reg);
#else
                fill_regs(td, &status->pr_reg);
#endif
                sbuf_bcat(sb, status, sizeof(*status));
                free(status, M_TEMP);
        }
        *sizep = sizeof(*status);
}

static void
__elfN(note_fpregset)(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct thread *td;
        elf_prfpregset_t *fpregset;

        td = arg;
        if (sb != NULL) {
                KASSERT(*sizep == sizeof(*fpregset), ("invalid size"));
                fpregset = malloc(sizeof(*fpregset), M_TEMP, M_ZERO | M_WAITOK);
#if defined(COMPAT_FREEBSD32) && __ELF_WORD_SIZE == 32
                fill_fpregs32(td, fpregset);
#else
                fill_fpregs(td, fpregset);
#endif
                sbuf_bcat(sb, fpregset, sizeof(*fpregset));
                free(fpregset, M_TEMP);
        }
        *sizep = sizeof(*fpregset);
}

static void
__elfN(note_thrmisc)(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct thread *td;
        elf_thrmisc_t thrmisc;

        td = arg;
        if (sb != NULL) {
                KASSERT(*sizep == sizeof(thrmisc), ("invalid size"));
                bzero(&thrmisc, sizeof(thrmisc));
                strcpy(thrmisc.pr_tname, td->td_name);
                sbuf_bcat(sb, &thrmisc, sizeof(thrmisc));
        }
        *sizep = sizeof(thrmisc);
}

static void
__elfN(note_ptlwpinfo)(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct thread *td;
        size_t size;
        int structsize;
#if defined(COMPAT_FREEBSD32) && __ELF_WORD_SIZE == 32
        struct ptrace_lwpinfo32 pl;
#else
        struct ptrace_lwpinfo pl;
#endif

        td = arg;
        size = sizeof(structsize) + sizeof(pl);
        if (sb != NULL) {
                KASSERT(*sizep == size, ("invalid size"));
                structsize = sizeof(pl);
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                bzero(&pl, sizeof(pl));
                pl.pl_lwpid = td->td_tid;
                pl.pl_event = PL_EVENT_NONE;
                pl.pl_sigmask = td->td_sigmask;
                pl.pl_siglist = td->td_siglist;
                if (td->td_si.si_signo != 0) {
                        pl.pl_event = PL_EVENT_SIGNAL;
                        pl.pl_flags |= PL_FLAG_SI;
#if defined(COMPAT_FREEBSD32) && __ELF_WORD_SIZE == 32
                        siginfo_to_siginfo32(&td->td_si, &pl.pl_siginfo);
#else
                        pl.pl_siginfo = td->td_si;
#endif
                }
                strcpy(pl.pl_tdname, td->td_name);
                /* XXX TODO: supply more information in struct ptrace_lwpinfo*/
                sbuf_bcat(sb, &pl, sizeof(pl));
        }
        *sizep = size;
}

/*
 * Allow for MD specific notes, as well as any MD
 * specific preparations for writing MI notes.
 */
static void
__elfN(note_threadmd)(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct thread *td;
        void *buf;
        size_t size;

        td = (struct thread *)arg;
        size = *sizep;
        if (size != 0 && sb != NULL)
                buf = malloc(size, M_TEMP, M_ZERO | M_WAITOK);
        else
                buf = NULL;
        size = 0;
        __elfN(dump_thread)(td, buf, &size);
        KASSERT(sb == NULL || *sizep == size, ("invalid size"));
        if (size != 0 && sb != NULL)
                sbuf_bcat(sb, buf, size);
        free(buf, M_TEMP);
        *sizep = size;
}

#ifdef KINFO_PROC_SIZE
CTASSERT(sizeof(struct kinfo_proc) == KINFO_PROC_SIZE);
#endif

static void
__elfN(note_procstat_proc)(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct proc *p;
        size_t size;
        int structsize;

        p = arg;
        size = sizeof(structsize) + p->p_numthreads *
            sizeof(elf_kinfo_proc_t);

        if (sb != NULL) {
                KASSERT(*sizep == size, ("invalid size"));
                structsize = sizeof(elf_kinfo_proc_t);
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                sx_slock(&proctree_lock);
                PROC_LOCK(p);
                kern_proc_out(p, sb, ELF_KERN_PROC_MASK);
                sx_sunlock(&proctree_lock);
        }
        *sizep = size;
}

#ifdef KINFO_FILE_SIZE
CTASSERT(sizeof(struct kinfo_file) == KINFO_FILE_SIZE);
#endif

static void
note_procstat_files(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct proc *p;
        size_t size, sect_sz, i;
        ssize_t start_len, sect_len;
        int structsize, filedesc_flags;

        if (coredump_pack_fileinfo)
                filedesc_flags = KERN_FILEDESC_PACK_KINFO;
        else
                filedesc_flags = 0;

        p = arg;
        structsize = sizeof(struct kinfo_file);
        if (sb == NULL) {
                size = 0;
                sb = sbuf_new(NULL, NULL, 128, SBUF_FIXEDLEN);
                sbuf_set_drain(sb, sbuf_count_drain, &size);
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                PROC_LOCK(p);
                kern_proc_filedesc_out(p, sb, -1, filedesc_flags);
                sbuf_finish(sb);
                sbuf_delete(sb);
                *sizep = size;
        } else {
                sbuf_start_section(sb, &start_len);

                sbuf_bcat(sb, &structsize, sizeof(structsize));
                PROC_LOCK(p);
                kern_proc_filedesc_out(p, sb, *sizep - sizeof(structsize),
                    filedesc_flags);

                sect_len = sbuf_end_section(sb, start_len, 0, 0);
                if (sect_len < 0)
                        return;
                sect_sz = sect_len;

                KASSERT(sect_sz <= *sizep,
                    ("kern_proc_filedesc_out did not respect maxlen; "
                     "requested %zu, got %zu", *sizep - sizeof(structsize),
                     sect_sz - sizeof(structsize)));

                for (i = 0; i < *sizep - sect_sz && sb->s_error == 0; i++)
                        sbuf_putc(sb, 0);
        }
}

#ifdef KINFO_VMENTRY_SIZE
CTASSERT(sizeof(struct kinfo_vmentry) == KINFO_VMENTRY_SIZE);
#endif

static void
note_procstat_vmmap(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct proc *p;
        size_t size;
        int structsize, vmmap_flags;

        if (coredump_pack_vmmapinfo)
                vmmap_flags = KERN_VMMAP_PACK_KINFO;
        else
                vmmap_flags = 0;

        p = arg;
        structsize = sizeof(struct kinfo_vmentry);
        if (sb == NULL) {
                size = 0;
                sb = sbuf_new(NULL, NULL, 128, SBUF_FIXEDLEN);
                sbuf_set_drain(sb, sbuf_count_drain, &size);
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                PROC_LOCK(p);
                kern_proc_vmmap_out(p, sb, -1, vmmap_flags);
                sbuf_finish(sb);
                sbuf_delete(sb);
                *sizep = size;
        } else {
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                PROC_LOCK(p);
                kern_proc_vmmap_out(p, sb, *sizep - sizeof(structsize),
                    vmmap_flags);
        }
}

static void
note_procstat_groups(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct proc *p;
        size_t size;
        int structsize;

        p = arg;
        size = sizeof(structsize) + p->p_ucred->cr_ngroups * sizeof(gid_t);
        if (sb != NULL) {
                KASSERT(*sizep == size, ("invalid size"));
                structsize = sizeof(gid_t);
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                sbuf_bcat(sb, p->p_ucred->cr_groups, p->p_ucred->cr_ngroups *
                    sizeof(gid_t));
        }
        *sizep = size;
}

static void
note_procstat_umask(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct proc *p;
        size_t size;
        int structsize;

        p = arg;
        size = sizeof(structsize) + sizeof(p->p_pd->pd_cmask);
        if (sb != NULL) {
                KASSERT(*sizep == size, ("invalid size"));
                structsize = sizeof(p->p_pd->pd_cmask);
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                sbuf_bcat(sb, &p->p_pd->pd_cmask, sizeof(p->p_pd->pd_cmask));
        }
        *sizep = size;
}

static void
note_procstat_rlimit(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct proc *p;
        struct rlimit rlim[RLIM_NLIMITS];
        size_t size;
        int structsize, i;

        p = arg;
        size = sizeof(structsize) + sizeof(rlim);
        if (sb != NULL) {
                KASSERT(*sizep == size, ("invalid size"));
                structsize = sizeof(rlim);
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                PROC_LOCK(p);
                for (i = 0; i < RLIM_NLIMITS; i++)
                        lim_rlimit_proc(p, i, &rlim[i]);
                PROC_UNLOCK(p);
                sbuf_bcat(sb, rlim, sizeof(rlim));
        }
        *sizep = size;
}

static void
note_procstat_osrel(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct proc *p;
        size_t size;
        int structsize;

        p = arg;
        size = sizeof(structsize) + sizeof(p->p_osrel);
        if (sb != NULL) {
                KASSERT(*sizep == size, ("invalid size"));
                structsize = sizeof(p->p_osrel);
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                sbuf_bcat(sb, &p->p_osrel, sizeof(p->p_osrel));
        }
        *sizep = size;
}

static void
__elfN(note_procstat_psstrings)(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct proc *p;
        elf_ps_strings_t ps_strings;
        size_t size;
        int structsize;

        p = arg;
        size = sizeof(structsize) + sizeof(ps_strings);
        if (sb != NULL) {
                KASSERT(*sizep == size, ("invalid size"));
                structsize = sizeof(ps_strings);
#if defined(COMPAT_FREEBSD32) && __ELF_WORD_SIZE == 32
                ps_strings = PTROUT(p->p_sysent->sv_psstrings);
#else
                ps_strings = p->p_sysent->sv_psstrings;
#endif
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                sbuf_bcat(sb, &ps_strings, sizeof(ps_strings));
        }
        *sizep = size;
}

static void
__elfN(note_procstat_auxv)(void *arg, struct sbuf *sb, size_t *sizep)
{
        struct proc *p;
        size_t size;
        int structsize;

        p = arg;
        if (sb == NULL) {
                size = 0;
                sb = sbuf_new(NULL, NULL, AT_COUNT * sizeof(Elf_Auxinfo),
                    SBUF_FIXEDLEN);
                sbuf_set_drain(sb, sbuf_count_drain, &size);
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                PHOLD(p);
                proc_getauxv(curthread, p, sb);
                PRELE(p);
                sbuf_finish(sb);
                sbuf_delete(sb);
                *sizep = size;
        } else {
                structsize = sizeof(Elf_Auxinfo);
                sbuf_bcat(sb, &structsize, sizeof(structsize));
                PHOLD(p);
                proc_getauxv(curthread, p, sb);
                PRELE(p);
        }
}

static bool
__elfN(parse_notes)(struct image_params *imgp, Elf_Note *checknote,
    const char *note_vendor, const Elf_Phdr *pnote,
    bool (*cb)(const Elf_Note *, void *, bool *), void *cb_arg)
{
        const Elf_Note *note, *note0, *note_end;
        const char *note_name;
        char *buf;
        int i, error;
        bool res;

        /* We need some limit, might as well use PAGE_SIZE. */
        if (pnote == NULL || pnote->p_filesz > PAGE_SIZE)
                return (false);
        ASSERT_VOP_LOCKED(imgp->vp, "parse_notes");
        if (pnote->p_offset > PAGE_SIZE ||
            pnote->p_filesz > PAGE_SIZE - pnote->p_offset) {
                buf = malloc(pnote->p_filesz, M_TEMP, M_NOWAIT);
                if (buf == NULL) {
                        VOP_UNLOCK(imgp->vp);
                        buf = malloc(pnote->p_filesz, M_TEMP, M_WAITOK);
                        vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
                }
                error = vn_rdwr(UIO_READ, imgp->vp, buf, pnote->p_filesz,
                    pnote->p_offset, UIO_SYSSPACE, IO_NODELOCKED,
                    curthread->td_ucred, NOCRED, NULL, curthread);
                if (error != 0) {
                        uprintf("i/o error PT_NOTE\n");
                        goto retf;
                }
                note = note0 = (const Elf_Note *)buf;
                note_end = (const Elf_Note *)(buf + pnote->p_filesz);
        } else {
                note = note0 = (const Elf_Note *)(imgp->image_header +
                    pnote->p_offset);
                note_end = (const Elf_Note *)(imgp->image_header +
                    pnote->p_offset + pnote->p_filesz);
                buf = NULL;
        }
        for (i = 0; i < 100 && note >= note0 && note < note_end; i++) {
                if (!aligned(note, Elf32_Addr) || (const char *)note_end -
                    (const char *)note < sizeof(Elf_Note)) {
                        goto retf;
                }
                if (note->n_namesz != checknote->n_namesz ||
                    note->n_descsz != checknote->n_descsz ||
                    note->n_type != checknote->n_type)
                        goto nextnote;
                note_name = (const char *)(note + 1);
                if (note_name + checknote->n_namesz >=
                    (const char *)note_end || strncmp(note_vendor,
                    note_name, checknote->n_namesz) != 0)
                        goto nextnote;

                if (cb(note, cb_arg, &res))
                        goto ret;
nextnote:
                note = (const Elf_Note *)((const char *)(note + 1) +
                    roundup2(note->n_namesz, ELF_NOTE_ROUNDSIZE) +
                    roundup2(note->n_descsz, ELF_NOTE_ROUNDSIZE));
        }
retf:
        res = false;
ret:
        free(buf, M_TEMP);
        return (res);
}

struct brandnote_cb_arg {
        Elf_Brandnote *brandnote;
        int32_t *osrel;
};

static bool
brandnote_cb(const Elf_Note *note, void *arg0, bool *res)
{
        struct brandnote_cb_arg *arg;

        arg = arg0;

        /*
         * Fetch the osreldate for binary from the ELF OSABI-note if
         * necessary.
         */
        *res = (arg->brandnote->flags & BN_TRANSLATE_OSREL) != 0 &&
            arg->brandnote->trans_osrel != NULL ?
            arg->brandnote->trans_osrel(note, arg->osrel) : true;

        return (true);
}

static Elf_Note fctl_note = {
        .n_namesz = sizeof(FREEBSD_ABI_VENDOR),
        .n_descsz = sizeof(uint32_t),
        .n_type = NT_FREEBSD_FEATURE_CTL,
};

struct fctl_cb_arg {
        bool *has_fctl0;
        uint32_t *fctl0;
};

static bool
note_fctl_cb(const Elf_Note *note, void *arg0, bool *res)
{
        struct fctl_cb_arg *arg;
        const Elf32_Word *desc;
        uintptr_t p;

        arg = arg0;
        p = (uintptr_t)(note + 1);
        p += roundup2(note->n_namesz, ELF_NOTE_ROUNDSIZE);
        desc = (const Elf32_Word *)p;
        *arg->has_fctl0 = true;
        *arg->fctl0 = desc[0];
        *res = true;
        return (true);
}

/*
 * Try to find the appropriate ABI-note section for checknote, fetch
 * the osreldate and feature control flags for binary from the ELF
 * OSABI-note.  Only the first page of the image is searched, the same
 * as for headers.
 */
static bool
__elfN(check_note)(struct image_params *imgp, Elf_Brandnote *brandnote,
    int32_t *osrel, bool *has_fctl0, uint32_t *fctl0)
{
        const Elf_Phdr *phdr;
        const Elf_Ehdr *hdr;
        struct brandnote_cb_arg b_arg;
        struct fctl_cb_arg f_arg;
        int i, j;

        hdr = (const Elf_Ehdr *)imgp->image_header;
        phdr = (const Elf_Phdr *)(imgp->image_header + hdr->e_phoff);
        b_arg.brandnote = brandnote;
        b_arg.osrel = osrel;
        f_arg.has_fctl0 = has_fctl0;
        f_arg.fctl0 = fctl0;

        for (i = 0; i < hdr->e_phnum; i++) {
                if (phdr[i].p_type == PT_NOTE && __elfN(parse_notes)(imgp,
                    &brandnote->hdr, brandnote->vendor, &phdr[i], brandnote_cb,
                    &b_arg)) {
                        for (j = 0; j < hdr->e_phnum; j++) {
                                if (phdr[j].p_type == PT_NOTE &&
                                    __elfN(parse_notes)(imgp, &fctl_note,
                                    FREEBSD_ABI_VENDOR, &phdr[j],
                                    note_fctl_cb, &f_arg))
                                        break;
                        }
                        return (true);
                }
        }
        return (false);

}

/*
 * Tell kern_execve.c about it, with a little help from the linker.
 */
static struct execsw __elfN(execsw) = {
        .ex_imgact = __CONCAT(exec_, __elfN(imgact)),
        .ex_name = __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE))
};
EXEC_SET(__CONCAT(elf, __ELF_WORD_SIZE), __elfN(execsw));

static vm_prot_t
__elfN(trans_prot)(Elf_Word flags)
{
        vm_prot_t prot;

        prot = 0;
        if (flags & PF_X)
                prot |= VM_PROT_EXECUTE;
        if (flags & PF_W)
                prot |= VM_PROT_WRITE;
        if (flags & PF_R)
                prot |= VM_PROT_READ;
#if __ELF_WORD_SIZE == 32 && (defined(__amd64__) || defined(__i386__))
        if (i386_read_exec && (flags & PF_R))
                prot |= VM_PROT_EXECUTE;
#endif
        return (prot);
}

static Elf_Word
__elfN(untrans_prot)(vm_prot_t prot)
{
        Elf_Word flags;

        flags = 0;
        if (prot & VM_PROT_EXECUTE)
                flags |= PF_X;
        if (prot & VM_PROT_READ)
                flags |= PF_R;
        if (prot & VM_PROT_WRITE)
                flags |= PF_W;
        return (flags);
}

vm_size_t
__elfN(stackgap)(struct image_params *imgp, uintptr_t *stack_base)
{
        uintptr_t range, rbase, gap;
        int pct;

        pct = __elfN(aslr_stack_gap);
        if (pct == 0)
                return (0);
        if (pct > 50)
                pct = 50;
        range = imgp->eff_stack_sz * pct / 100;
        arc4rand(&rbase, sizeof(rbase), 0);
        gap = rbase % range;
        gap &= ~(sizeof(u_long) - 1);
        *stack_base -= gap;
        return (gap);
}