sys/kern/kern_sharedpage.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2010, 2012 Konstantin Belousov <kib@FreeBSD.org>
   5  * Copyright (c) 2015 The FreeBSD Foundation
   6  * All rights reserved.
   7  *
   8  * Portions of this software were developed by Konstantin Belousov
   9  * under sponsorship from the FreeBSD Foundation.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <sys/cdefs.h>
  34 __FBSDID("$FreeBSD$");
  35
  36 #include "opt_vm.h"
  37
  38 #include <sys/param.h>
  39 #include <sys/systm.h>
  40 #include <sys/kernel.h>
  41 #include <sys/lock.h>
  42 #include <sys/malloc.h>
  43 #include <sys/rwlock.h>
  44 #include <sys/stddef.h>
  45 #include <sys/sysent.h>
  46 #include <sys/sysctl.h>
  47 #include <sys/vdso.h>
  48
  49 #include <vm/vm.h>
  50 #include <vm/vm_param.h>
  51 #include <vm/pmap.h>
  52 #include <vm/vm_extern.h>
  53 #include <vm/vm_kern.h>
  54 #include <vm/vm_map.h>
  55 #include <vm/vm_object.h>
  56 #include <vm/vm_page.h>
  57 #include <vm/vm_pager.h>
  58
  59 static struct sx shared_page_alloc_sx;
  60 static vm_object_t shared_page_obj;
  61 static int shared_page_free;
  62 char *shared_page_mapping;
  63
  64 #ifdef RANDOM_FENESTRASX
  65 static struct vdso_fxrng_generation *fxrng_shpage_mapping;
  66
  67 static bool fxrng_enabled = true;
  68 SYSCTL_BOOL(_debug, OID_AUTO, fxrng_vdso_enable, CTLFLAG_RWTUN, &fxrng_enabled,
  69     0, "Enable FXRNG VDSO");
  70 #endif
  71
  72 void
  73 shared_page_write(int base, int size, const void *data)
  74 {
  75
  76         bcopy(data, shared_page_mapping + base, size);
  77 }
  78
  79 static int
  80 shared_page_alloc_locked(int size, int align)
  81 {
  82         int res;
  83
  84         res = roundup(shared_page_free, align);
  85         if (res + size >= IDX_TO_OFF(shared_page_obj->size))
  86                 res = -1;
  87         else
  88                 shared_page_free = res + size;
  89         return (res);
  90 }
  91
  92 int
  93 shared_page_alloc(int size, int align)
  94 {
  95         int res;
  96
  97         sx_xlock(&shared_page_alloc_sx);
  98         res = shared_page_alloc_locked(size, align);
  99         sx_xunlock(&shared_page_alloc_sx);
 100         return (res);
 101 }
 102
 103 int
 104 shared_page_fill(int size, int align, const void *data)
 105 {
 106         int res;
 107
 108         sx_xlock(&shared_page_alloc_sx);
 109         res = shared_page_alloc_locked(size, align);
 110         if (res != -1)
 111                 shared_page_write(res, size, data);
 112         sx_xunlock(&shared_page_alloc_sx);
 113         return (res);
 114 }
 115
 116 static void
 117 shared_page_init(void *dummy __unused)
 118 {
 119         vm_page_t m;
 120         vm_offset_t addr;
 121
 122         sx_init(&shared_page_alloc_sx, "shpsx");
 123         shared_page_obj = vm_pager_allocate(OBJT_PHYS, 0, PAGE_SIZE,
 124             VM_PROT_DEFAULT, 0, NULL);
 125         VM_OBJECT_WLOCK(shared_page_obj);
 126         m = vm_page_grab(shared_page_obj, 0, VM_ALLOC_ZERO);
 127         VM_OBJECT_WUNLOCK(shared_page_obj);
 128         vm_page_valid(m);
 129         vm_page_xunbusy(m);
 130         addr = kva_alloc(PAGE_SIZE);
 131         pmap_qenter(addr, &m, 1);
 132         shared_page_mapping = (char *)addr;
 133 }
 134
 135 SYSINIT(shp, SI_SUB_EXEC, SI_ORDER_FIRST, (sysinit_cfunc_t)shared_page_init,
 136     NULL);
 137
 138 /*
 139  * Push the timehands update to the shared page.
 140  *
 141  * The lockless update scheme is similar to the one used to update the
 142  * in-kernel timehands, see sys/kern/kern_tc.c:tc_windup() (which
 143  * calls us after the timehands are updated).
 144  */
 145 static void
 146 timehands_update(struct vdso_sv_tk *svtk)
 147 {
 148         struct vdso_timehands th;
 149         struct vdso_timekeep *tk;
 150         uint32_t enabled, idx;
 151
 152         enabled = tc_fill_vdso_timehands(&th);
 153         th.th_gen = 0;
 154         idx = svtk->sv_timekeep_curr;
 155         if (++idx >= VDSO_TH_NUM)
 156                 idx = 0;
 157         svtk->sv_timekeep_curr = idx;
 158         if (++svtk->sv_timekeep_gen == 0)
 159                 svtk->sv_timekeep_gen = 1;
 160
 161         tk = (struct vdso_timekeep *)(shared_page_mapping +
 162             svtk->sv_timekeep_off);
 163         tk->tk_th[idx].th_gen = 0;
 164         atomic_thread_fence_rel();
 165         if (enabled)
 166                 tk->tk_th[idx] = th;
 167         atomic_store_rel_32(&tk->tk_th[idx].th_gen, svtk->sv_timekeep_gen);
 168         atomic_store_rel_32(&tk->tk_current, idx);
 169
 170         /*
 171          * The ordering of the assignment to tk_enabled relative to
 172          * the update of the vdso_timehands is not important.
 173          */
 174         tk->tk_enabled = enabled;
 175 }
 176
 177 #ifdef COMPAT_FREEBSD32
 178 static void
 179 timehands_update32(struct vdso_sv_tk *svtk)
 180 {
 181         struct vdso_timehands32 th;
 182         struct vdso_timekeep32 *tk;
 183         uint32_t enabled, idx;
 184
 185         enabled = tc_fill_vdso_timehands32(&th);
 186         th.th_gen = 0;
 187         idx = svtk->sv_timekeep_curr;
 188         if (++idx >= VDSO_TH_NUM)
 189                 idx = 0;
 190         svtk->sv_timekeep_curr = idx;
 191         if (++svtk->sv_timekeep_gen == 0)
 192                 svtk->sv_timekeep_gen = 1;
 193
 194         tk = (struct vdso_timekeep32 *)(shared_page_mapping +
 195             svtk->sv_timekeep_off);
 196         tk->tk_th[idx].th_gen = 0;
 197         atomic_thread_fence_rel();
 198         if (enabled)
 199                 tk->tk_th[idx] = th;
 200         atomic_store_rel_32(&tk->tk_th[idx].th_gen, svtk->sv_timekeep_gen);
 201         atomic_store_rel_32(&tk->tk_current, idx);
 202         tk->tk_enabled = enabled;
 203 }
 204 #endif
 205
 206 /*
 207  * This is hackish, but easiest way to avoid creating list structures
 208  * that needs to be iterated over from the hardclock interrupt
 209  * context.
 210  */
 211 static struct vdso_sv_tk *host_svtk;
 212 #ifdef COMPAT_FREEBSD32
 213 static struct vdso_sv_tk *compat32_svtk;
 214 #endif
 215
 216 void
 217 timekeep_push_vdso(void)
 218 {
 219
 220         if (host_svtk != NULL)
 221                 timehands_update(host_svtk);
 222 #ifdef COMPAT_FREEBSD32
 223         if (compat32_svtk != NULL)
 224                 timehands_update32(compat32_svtk);
 225 #endif
 226 }
 227
 228 struct vdso_sv_tk *
 229 alloc_sv_tk(void)
 230 {
 231         struct vdso_sv_tk *svtk;
 232         int tk_base;
 233         uint32_t tk_ver;
 234
 235         tk_ver = VDSO_TK_VER_CURR;
 236         svtk = malloc(sizeof(struct vdso_sv_tk), M_TEMP, M_WAITOK | M_ZERO);
 237         tk_base = shared_page_alloc(sizeof(struct vdso_timekeep) +
 238             sizeof(struct vdso_timehands) * VDSO_TH_NUM, 16);
 239         KASSERT(tk_base != -1, ("tk_base -1 for native"));
 240         shared_page_write(tk_base + offsetof(struct vdso_timekeep, tk_ver),
 241             sizeof(uint32_t), &tk_ver);
 242         svtk->sv_timekeep_off = tk_base;
 243         timekeep_push_vdso();
 244         return (svtk);
 245 }
 246
 247 #ifdef COMPAT_FREEBSD32
 248 struct vdso_sv_tk *
 249 alloc_sv_tk_compat32(void)
 250 {
 251         struct vdso_sv_tk *svtk;
 252         int tk_base;
 253         uint32_t tk_ver;
 254
 255         svtk = malloc(sizeof(struct vdso_sv_tk), M_TEMP, M_WAITOK | M_ZERO);
 256         tk_ver = VDSO_TK_VER_CURR;
 257         tk_base = shared_page_alloc(sizeof(struct vdso_timekeep32) +
 258             sizeof(struct vdso_timehands32) * VDSO_TH_NUM, 16);
 259         KASSERT(tk_base != -1, ("tk_base -1 for 32bit"));
 260         shared_page_write(tk_base + offsetof(struct vdso_timekeep32,
 261             tk_ver), sizeof(uint32_t), &tk_ver);
 262         svtk->sv_timekeep_off = tk_base;
 263         timekeep_push_vdso();
 264         return (svtk);
 265 }
 266 #endif
 267
 268 #ifdef RANDOM_FENESTRASX
 269 void
 270 fxrng_push_seed_generation(uint64_t gen)
 271 {
 272         if (fxrng_shpage_mapping == NULL || !fxrng_enabled)
 273                 return;
 274         KASSERT(gen < INT32_MAX,
 275             ("fxrng seed version shouldn't roll over a 32-bit counter "
 276              "for approximately 456,000 years"));
 277         atomic_store_rel_32(&fxrng_shpage_mapping->fx_generation32,
 278             (uint32_t)gen);
 279 }
 280
 281 static void
 282 alloc_sv_fxrng_generation(void)
 283 {
 284         int base;
 285
 286         /*
 287          * Allocate a full cache line for the fxrng root generation (64-bit
 288          * counter, or truncated 32-bit counter on ILP32 userspace).  It is
 289          * important that the line is not shared with frequently dirtied data,
 290          * and the shared page allocator lacks a __read_mostly mechanism.
 291          * However, PAGE_SIZE is typically large relative to the amount of
 292          * stuff we've got in it so far, so maybe the possible waste isn't an
 293          * issue.
 294          */
 295         base = shared_page_alloc(CACHE_LINE_SIZE, CACHE_LINE_SIZE);
 296         KASSERT(base != -1, ("%s: base allocation failed", __func__));
 297         fxrng_shpage_mapping = (void *)(shared_page_mapping + base);
 298         *fxrng_shpage_mapping = (struct vdso_fxrng_generation) {
 299                 .fx_vdso_version = VDSO_FXRNG_VER_CURR,
 300         };
 301 }
 302 #endif /* RANDOM_FENESTRASX */
 303
 304 void
 305 exec_sysvec_init(void *param)
 306 {
 307         struct sysentvec *sv;
 308 #ifdef RANDOM_FENESTRASX
 309         ptrdiff_t base;
 310 #endif
 311
 312         sv = (struct sysentvec *)param;
 313         if ((sv->sv_flags & SV_SHP) == 0)
 314                 return;
 315         sv->sv_shared_page_obj = shared_page_obj;
 316         sv->sv_sigcode_base = sv->sv_shared_page_base +
 317             shared_page_fill(*(sv->sv_szsigcode), 16, sv->sv_sigcode);
 318         if ((sv->sv_flags & SV_ABI_MASK) != SV_ABI_FREEBSD)
 319                 return;
 320         if ((sv->sv_flags & SV_TIMEKEEP) != 0) {
 321 #ifdef COMPAT_FREEBSD32
 322                 if ((sv->sv_flags & SV_ILP32) != 0) {
 323                         KASSERT(compat32_svtk == NULL,
 324                             ("Compat32 already registered"));
 325                         compat32_svtk = alloc_sv_tk_compat32();
 326                         sv->sv_timekeep_base = sv->sv_shared_page_base +
 327                             compat32_svtk->sv_timekeep_off;
 328                 } else {
 329 #endif
 330                         KASSERT(host_svtk == NULL, ("Host already registered"));
 331                         host_svtk = alloc_sv_tk();
 332                         sv->sv_timekeep_base = sv->sv_shared_page_base +
 333                             host_svtk->sv_timekeep_off;
 334 #ifdef COMPAT_FREEBSD32
 335                 }
 336 #endif
 337         }
 338 #ifdef RANDOM_FENESTRASX
 339         if ((sv->sv_flags & SV_RNG_SEED_VER) != 0) {
 340                 /*
 341                  * Only allocate a single VDSO entry for multiple sysentvecs,
 342                  * i.e., native and COMPAT32.
 343                  */
 344                 if (fxrng_shpage_mapping == NULL)
 345                         alloc_sv_fxrng_generation();
 346                 base = (char *)fxrng_shpage_mapping - shared_page_mapping;
 347                 sv->sv_fxrng_gen_base = sv->sv_shared_page_base + base;
 348         }
 349 #endif
 350 }
 351
 352 void
 353 exec_sysvec_init_secondary(struct sysentvec *sv, struct sysentvec *sv2)
 354 {
 355         MPASS((sv2->sv_flags & SV_ABI_MASK) == (sv->sv_flags & SV_ABI_MASK));
 356         MPASS((sv2->sv_flags & SV_TIMEKEEP) == (sv->sv_flags & SV_TIMEKEEP));
 357         MPASS((sv2->sv_flags & SV_SHP) != 0 && (sv->sv_flags & SV_SHP) != 0);
 358         MPASS((sv2->sv_flags & SV_RNG_SEED_VER) ==
 359             (sv->sv_flags & SV_RNG_SEED_VER));
 360
 361         sv2->sv_shared_page_obj = sv->sv_shared_page_obj;
 362         sv2->sv_sigcode_base = sv2->sv_shared_page_base +
 363             (sv->sv_sigcode_base - sv->sv_shared_page_base);
 364         if ((sv2->sv_flags & SV_ABI_MASK) != SV_ABI_FREEBSD)
 365                 return;
 366         if ((sv2->sv_flags & SV_TIMEKEEP) != 0) {
 367                 sv2->sv_timekeep_base = sv2->sv_shared_page_base +
 368                     (sv->sv_timekeep_base - sv->sv_shared_page_base);
 369         }
 370         if ((sv2->sv_flags & SV_RNG_SEED_VER) != 0) {
 371                 sv2->sv_fxrng_gen_base = sv2->sv_shared_page_base +
 372                     (sv->sv_fxrng_gen_base - sv->sv_shared_page_base);
 373         }
 374 }