elf_trampoline.c

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    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 <machine/elf.h>
   45 #include <machine/cpufunc.h>
   46 #include <machine/stdarg.h>
   47 
   48 #ifndef KERNNAME
   49 #error Kernel name not provided
   50 #endif
   51 
   52 extern char kernel_start[];
   53 extern char kernel_end[];
   54 
   55 static __inline void *
   56 memcpy(void *dst, const void *src, size_t len)
   57 {
   58         const char *s = src;
   59         char *d = dst;
   60 
   61         while (len) {
   62                 if (0 && len >= 4 && !((vm_offset_t)d & 3) &&
   63                     !((vm_offset_t)s & 3)) {
   64                         *(uint32_t *)d = *(uint32_t *)s;
   65                         s += 4;
   66                         d += 4;
   67                         len -= 4;
   68                 } else {
   69                         *d++ = *s++;
   70                         len--;
   71                 }
   72         }
   73         return (dst);
   74 }
   75 
   76 static __inline void
   77 bzero(void *addr, size_t count)
   78 {
   79         char *tmp = (char *)addr;
   80 
   81         while (count > 0) {
   82                 if (count >= 4 && !((vm_offset_t)tmp & 3)) {
   83                         *(uint32_t *)tmp = 0;
   84                         tmp += 4;
   85                         count -= 4;
   86                 } else {
   87                         *tmp = 0;
   88                         tmp++;
   89                         count--;
   90                 }
   91         }
   92 }
   93 
   94 /*
   95  * Convert number to pointer, truncate on 64->32 case, sign extend
   96  * in 32->64 case
   97  */
   98 #define mkptr(x)        ((void *)(intptr_t)(int)(x))
   99 
  100 /*
  101  * Relocate PT_LOAD segments of kernel ELF image to their respective
  102  * virtual addresses and return entry point
  103  */
  104 void *
  105 load_kernel(void * kstart)
  106 {
  107 #if ELFSIZE == 64
  108         Elf64_Ehdr *eh;
  109         Elf64_Phdr phdr[64] /* XXX */;
  110         Elf64_Shdr shdr[64] /* XXX */;
  111 #else
  112         Elf32_Ehdr *eh;
  113         Elf32_Phdr phdr[64] /* XXX */;
  114         Elf32_Shdr shdr[64] /* XXX */;
  115 #endif
  116         int i, j;
  117         void *entry_point;
  118         vm_offset_t loadend = 0;
  119         intptr_t lastaddr;
  120         int symtabindex = -1;
  121         int symstrindex = -1;
  122         Elf_Size tmp;
  123         
  124 #if ELFSIZE == 64
  125         eh = (Elf64_Ehdr *)kstart;
  126 #else
  127         eh = (Elf32_Ehdr *)kstart;
  128 #endif
  129         entry_point = mkptr(eh->e_entry);
  130         memcpy(phdr, (void *)(kstart + eh->e_phoff),
  131             eh->e_phnum * sizeof(phdr[0]));
  132 
  133         memcpy(shdr, (void *)(kstart + eh->e_shoff),
  134             sizeof(*shdr) * eh->e_shnum);
  135 
  136         if (eh->e_shnum * eh->e_shentsize != 0 && eh->e_shoff != 0) {
  137                 for (i = 0; i < eh->e_shnum; i++) {
  138                         if (shdr[i].sh_type == SHT_SYMTAB) {
  139                                 /*
  140                                  * XXX: check if .symtab is in PT_LOAD?
  141                                  */
  142                                 if (shdr[i].sh_offset != 0 && 
  143                                     shdr[i].sh_size != 0) {
  144                                         symtabindex = i;
  145                                         symstrindex = shdr[i].sh_link;
  146                                 }
  147                         }
  148                 }
  149         }
  150 
  151         /*
  152          * Copy loadable segments
  153          */
  154         for (i = 0; i < eh->e_phnum; i++) {
  155                 volatile char c;
  156 
  157                 if (phdr[i].p_type != PT_LOAD)
  158                         continue;
  159                 
  160                 memcpy(mkptr(phdr[i].p_vaddr),
  161                     (void*)(kstart + phdr[i].p_offset), phdr[i].p_filesz);
  162 
  163                 /* Clean space from oversized segments, eg: bss. */
  164                 if (phdr[i].p_filesz < phdr[i].p_memsz)
  165                         bzero(mkptr(phdr[i].p_vaddr + phdr[i].p_filesz),
  166                             phdr[i].p_memsz - phdr[i].p_filesz);
  167 
  168                 if (loadend < phdr[i].p_vaddr + phdr[i].p_memsz)
  169                         loadend = phdr[i].p_vaddr + phdr[i].p_memsz;
  170         }
  171 
  172         /* Now grab the symbol tables. */
  173         lastaddr = (intptr_t)(int)loadend;
  174         if (symtabindex >= 0 && symstrindex >= 0) {
  175                 tmp = SYMTAB_MAGIC;
  176                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  177                 lastaddr += sizeof(Elf_Size);
  178                 tmp = shdr[symtabindex].sh_size +
  179                     shdr[symstrindex].sh_size + 2*sizeof(Elf_Size);
  180                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  181                 lastaddr += sizeof(Elf_Size);
  182                 /* .symtab size */
  183                 tmp = shdr[symtabindex].sh_size;
  184                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  185                 lastaddr += sizeof(shdr[symtabindex].sh_size);
  186                 /* .symtab data */
  187                 memcpy((void*)lastaddr,
  188                     shdr[symtabindex].sh_offset + kstart,
  189                     shdr[symtabindex].sh_size);
  190                 lastaddr += shdr[symtabindex].sh_size;
  191 
  192                 /* .strtab size */
  193                 tmp = shdr[symstrindex].sh_size;
  194                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  195                 lastaddr += sizeof(shdr[symstrindex].sh_size);
  196 
  197                 /* .strtab data */
  198                 memcpy((void*)lastaddr,
  199                     shdr[symstrindex].sh_offset + kstart,
  200                     shdr[symstrindex].sh_size);
  201         } else {
  202                 /* Do not take any chances */
  203                 tmp = 0;
  204                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  205         }
  206 
  207         return entry_point;
  208 }
  209 
  210 void
  211 _startC(register_t a0, register_t a1, register_t a2, register_t a3)
  212 {
  213         unsigned int * code;
  214         int i;
  215         void (*entry_point)(register_t, register_t, register_t, register_t);
  216 
  217         /* 
  218          * Relocate segment to the predefined memory location
  219          * Most likely it will be KSEG0/KSEG1 address
  220          */
  221         entry_point = load_kernel(kernel_start);
  222 
  223         /* Pass saved registers to original _start */
  224         entry_point(a0, a1, a2, a3);
  225 }

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FreeBSD/Linux Kernel Cross Reference sys/mips/mips/elf_trampoline.c

FreeBSD/Linux Kernel Cross Reference
sys/mips/mips/elf_trampoline.c