sys/mips/mips/elf_trampoline.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2005 Olivier Houchard.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include <sys/cdefs.h>
  28 __FBSDID("$FreeBSD$");
  29 #include <machine/asm.h>
  30 #include <sys/param.h>
  31
  32 #if ELFSIZE == 64
  33 #include <sys/elf64.h>
  34 #else
  35 #include <sys/elf32.h>
  36 #endif
  37
  38 /*
  39  * Since we are compiled outside of the normal kernel build process, we
  40  * need to include opt_global.h manually.
  41  */
  42 #include "opt_global.h"
  43
  44 #include <sys/inflate.h>
  45 #include <machine/elf.h>
  46 #include <machine/cpufunc.h>
  47 #include <machine/stdarg.h>
  48
  49 #ifndef KERNNAME
  50 #error Kernel name not provided
  51 #endif
  52
  53 extern char kernel_start[];
  54 extern char kernel_end[];
  55
  56 static __inline void *
  57 memcpy(void *dst, const void *src, size_t len)
  58 {
  59         const char *s = src;
  60         char *d = dst;
  61
  62         while (len) {
  63                 if (0 && len >= 4 && !((vm_offset_t)d & 3) &&
  64                     !((vm_offset_t)s & 3)) {
  65                         *(uint32_t *)d = *(uint32_t *)s;
  66                         s += 4;
  67                         d += 4;
  68                         len -= 4;
  69                 } else {
  70                         *d++ = *s++;
  71                         len--;
  72                 }
  73         }
  74         return (dst);
  75 }
  76
  77 static __inline void
  78 bzero(void *addr, size_t count)
  79 {
  80         char *tmp = (char *)addr;
  81
  82         while (count > 0) {
  83                 if (count >= 4 && !((vm_offset_t)tmp & 3)) {
  84                         *(uint32_t *)tmp = 0;
  85                         tmp += 4;
  86                         count -= 4;
  87                 } else {
  88                         *tmp = 0;
  89                         tmp++;
  90                         count--;
  91                 }
  92         }
  93 }
  94
  95 /*
  96  * Convert number to pointer, truncate on 64->32 case, sign extend
  97  * in 32->64 case
  98  */
  99 #define mkptr(x)        ((void *)(intptr_t)(int)(x))
 100
 101 /*
 102  * Relocate PT_LOAD segements of kernel ELF image to their respective
 103  * virtual addresses and return entry point
 104  */
 105 void *
 106 load_kernel(void * kstart)
 107 {
 108 #if ELFSIZE == 64
 109         Elf64_Ehdr *eh;
 110         Elf64_Phdr phdr[64] /* XXX */;
 111         Elf64_Shdr shdr[64] /* XXX */;
 112 #else
 113         Elf32_Ehdr *eh;
 114         Elf32_Phdr phdr[64] /* XXX */;
 115         Elf32_Shdr shdr[64] /* XXX */;
 116 #endif
 117         int i, j;
 118         void *entry_point;
 119         vm_offset_t loadend = 0;
 120         intptr_t lastaddr;
 121         int symtabindex = -1;
 122         int symstrindex = -1;
 123         Elf_Size tmp;
 124
 125 #if ELFSIZE == 64
 126         eh = (Elf64_Ehdr *)kstart;
 127 #else
 128         eh = (Elf32_Ehdr *)kstart;
 129 #endif
 130         entry_point = mkptr(eh->e_entry);
 131         memcpy(phdr, (void *)(kstart + eh->e_phoff),
 132             eh->e_phnum * sizeof(phdr[0]));
 133
 134         memcpy(shdr, (void *)(kstart + eh->e_shoff),
 135             sizeof(*shdr) * eh->e_shnum);
 136
 137         if (eh->e_shnum * eh->e_shentsize != 0 && eh->e_shoff != 0) {
 138                 for (i = 0; i < eh->e_shnum; i++) {
 139                         if (shdr[i].sh_type == SHT_SYMTAB) {
 140                                 /*
 141                                  * XXX: check if .symtab is in PT_LOAD?
 142                                  */
 143                                 if (shdr[i].sh_offset != 0 &&
 144                                     shdr[i].sh_size != 0) {
 145                                         symtabindex = i;
 146                                         symstrindex = shdr[i].sh_link;
 147                                 }
 148                         }
 149                 }
 150         }
 151
 152         /*
 153          * Copy loadable segments
 154          */
 155         for (i = 0; i < eh->e_phnum; i++) {
 156                 volatile char c;
 157
 158                 if (phdr[i].p_type != PT_LOAD)
 159                         continue;
 160
 161                 memcpy(mkptr(phdr[i].p_vaddr),
 162                     (void*)(kstart + phdr[i].p_offset), phdr[i].p_filesz);
 163
 164                 /* Clean space from oversized segments, eg: bss. */
 165                 if (phdr[i].p_filesz < phdr[i].p_memsz)
 166                         bzero(mkptr(phdr[i].p_vaddr + phdr[i].p_filesz),
 167                             phdr[i].p_memsz - phdr[i].p_filesz);
 168
 169                 if (loadend < phdr[i].p_vaddr + phdr[i].p_memsz)
 170                         loadend = phdr[i].p_vaddr + phdr[i].p_memsz;
 171         }
 172
 173         /* Now grab the symbol tables. */
 174         lastaddr = (intptr_t)(int)loadend;
 175         if (symtabindex >= 0 && symstrindex >= 0) {
 176                 tmp = SYMTAB_MAGIC;
 177                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
 178                 lastaddr += sizeof(Elf_Size);
 179                 tmp = shdr[symtabindex].sh_size +
 180                     shdr[symstrindex].sh_size + 2*sizeof(Elf_Size);
 181                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
 182                 lastaddr += sizeof(Elf_Size);
 183                 /* .symtab size */
 184                 tmp = shdr[symtabindex].sh_size;
 185                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
 186                 lastaddr += sizeof(shdr[symtabindex].sh_size);
 187                 /* .symtab data */
 188                 memcpy((void*)lastaddr,
 189                     shdr[symtabindex].sh_offset + kstart,
 190                     shdr[symtabindex].sh_size);
 191                 lastaddr += shdr[symtabindex].sh_size;
 192
 193                 /* .strtab size */
 194                 tmp = shdr[symstrindex].sh_size;
 195                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
 196                 lastaddr += sizeof(shdr[symstrindex].sh_size);
 197
 198                 /* .strtab data */
 199                 memcpy((void*)lastaddr,
 200                     shdr[symstrindex].sh_offset + kstart,
 201                     shdr[symstrindex].sh_size);
 202         } else {
 203                 /* Do not take any chances */
 204                 tmp = 0;
 205                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
 206         }
 207
 208         return entry_point;
 209 }
 210
 211 void
 212 _startC(register_t a0, register_t a1, register_t a2, register_t a3)
 213 {
 214         unsigned int * code;
 215         int i;
 216         void (*entry_point)(register_t, register_t, register_t, register_t);
 217
 218         /*
 219          * Relocate segment to the predefined memory location
 220          * Most likely it will be KSEG0/KSEG1 address
 221          */
 222         entry_point = load_kernel(kernel_start);
 223
 224         /* Pass saved registers to original _start */
 225         entry_point(a0, a1, a2, a3);
 226 }