elf_trampoline.c

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    1 /*-
    2  * Copyright (c) 2005 Olivier Houchard.  All rights reserved.
    3  *
    4  * Redistribution and use in source and binary forms, with or without
    5  * modification, are permitted provided that the following conditions
    6  * are met:
    7  * 1. Redistributions of source code must retain the above copyright
    8  *    notice, this list of conditions and the following disclaimer.
    9  * 2. Redistributions in binary form must reproduce the above copyright
   10  *    notice, this list of conditions and the following disclaimer in the
   11  *    documentation and/or other materials provided with the distribution.
   12  *
   13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   23  */
   24 
   25 #include <sys/cdefs.h>
   26 __FBSDID("$FreeBSD: releng/9.0/sys/mips/mips/elf_trampoline.c 224105 2011-07-16 17:22:01Z jchandra $");
   27 #include <machine/asm.h>
   28 #include <sys/param.h>
   29 
   30 #if ELFSIZE == 64
   31 #include <sys/elf64.h>
   32 #else
   33 #include <sys/elf32.h>
   34 #endif
   35 #include <sys/inflate.h>
   36 #include <machine/elf.h>
   37 #include <machine/cpufunc.h>
   38 #include <machine/stdarg.h>
   39 
   40 /*
   41  * Since we are compiled outside of the normal kernel build process, we
   42  * need to include opt_global.h manually.
   43  */
   44 #include "opt_global.h"
   45 
   46 #ifndef KERNNAME
   47 #error Kernel name not provided
   48 #endif
   49 
   50 extern char kernel_start[];
   51 extern char kernel_end[];
   52 
   53 static __inline void *
   54 memcpy(void *dst, const void *src, size_t len)
   55 {
   56         const char *s = src;
   57         char *d = dst;
   58 
   59         while (len) {
   60                 if (0 && len >= 4 && !((vm_offset_t)d & 3) &&
   61                     !((vm_offset_t)s & 3)) {
   62                         *(uint32_t *)d = *(uint32_t *)s;
   63                         s += 4;
   64                         d += 4;
   65                         len -= 4;
   66                 } else {
   67                         *d++ = *s++;
   68                         len--;
   69                 }
   70         }
   71         return (dst);
   72 }
   73 
   74 static __inline void
   75 bzero(void *addr, size_t count)
   76 {
   77         char *tmp = (char *)addr;
   78 
   79         while (count > 0) {
   80                 if (count >= 4 && !((vm_offset_t)tmp & 3)) {
   81                         *(uint32_t *)tmp = 0;
   82                         tmp += 4;
   83                         count -= 4;
   84                 } else {
   85                         *tmp = 0;
   86                         tmp++;
   87                         count--;
   88                 }
   89         }
   90 }
   91 
   92 /*
   93  * Convert number to pointer, truncate on 64->32 case, sign extend
   94  * in 32->64 case
   95  */
   96 #define mkptr(x)        ((void *)(intptr_t)(int)(x))
   97 
   98 /*
   99  * Relocate PT_LOAD segements of kernel ELF image to their respective
  100  * virtual addresses and return entry point
  101  */
  102 void *
  103 load_kernel(void * kstart)
  104 {
  105 #if ELFSIZE == 64
  106         Elf64_Ehdr *eh;
  107         Elf64_Phdr phdr[64] /* XXX */;
  108         Elf64_Shdr shdr[64] /* XXX */;
  109 #else
  110         Elf32_Ehdr *eh;
  111         Elf32_Phdr phdr[64] /* XXX */;
  112         Elf32_Shdr shdr[64] /* XXX */;
  113 #endif
  114         int i, j;
  115         void *entry_point;
  116         vm_offset_t loadend = 0;
  117         intptr_t lastaddr;
  118         int symtabindex = -1;
  119         int symstrindex = -1;
  120         Elf_Size tmp;
  121         
  122 #if ELFSIZE == 64
  123         eh = (Elf64_Ehdr *)kstart;
  124 #else
  125         eh = (Elf32_Ehdr *)kstart;
  126 #endif
  127         entry_point = mkptr(eh->e_entry);
  128         memcpy(phdr, (void *)(kstart + eh->e_phoff),
  129             eh->e_phnum * sizeof(phdr[0]));
  130 
  131         memcpy(shdr, (void *)(kstart + eh->e_shoff),
  132             sizeof(*shdr) * eh->e_shnum);
  133 
  134         if (eh->e_shnum * eh->e_shentsize != 0 && eh->e_shoff != 0) {
  135                 for (i = 0; i < eh->e_shnum; i++) {
  136                         if (shdr[i].sh_type == SHT_SYMTAB) {
  137                                 /*
  138                                  * XXX: check if .symtab is in PT_LOAD?
  139                                  */
  140                                 if (shdr[i].sh_offset != 0 && 
  141                                     shdr[i].sh_size != 0) {
  142                                         symtabindex = i;
  143                                         symstrindex = shdr[i].sh_link;
  144                                 }
  145                         }
  146                 }
  147         }
  148 
  149         /*
  150          * Copy loadable segments
  151          */
  152         for (i = 0; i < eh->e_phnum; i++) {
  153                 volatile char c;
  154 
  155                 if (phdr[i].p_type != PT_LOAD)
  156                         continue;
  157                 
  158                 memcpy(mkptr(phdr[i].p_vaddr),
  159                     (void*)(kstart + phdr[i].p_offset), phdr[i].p_filesz);
  160 
  161                 /* Clean space from oversized segments, eg: bss. */
  162                 if (phdr[i].p_filesz < phdr[i].p_memsz)
  163                         bzero(mkptr(phdr[i].p_vaddr + phdr[i].p_filesz),
  164                             phdr[i].p_memsz - phdr[i].p_filesz);
  165 
  166                 if (loadend < phdr[i].p_vaddr + phdr[i].p_memsz)
  167                         loadend = phdr[i].p_vaddr + phdr[i].p_memsz;
  168         }
  169 
  170         /* Now grab the symbol tables. */
  171         lastaddr = (intptr_t)(int)loadend;
  172         if (symtabindex >= 0 && symstrindex >= 0) {
  173                 tmp = SYMTAB_MAGIC;
  174                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  175                 lastaddr += sizeof(Elf_Size);
  176                 tmp = shdr[symtabindex].sh_size +
  177                     shdr[symstrindex].sh_size + 2*sizeof(Elf_Size);
  178                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  179                 lastaddr += sizeof(Elf_Size);
  180                 /* .symtab size */
  181                 tmp = shdr[symtabindex].sh_size;
  182                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  183                 lastaddr += sizeof(shdr[symtabindex].sh_size);
  184                 /* .symtab data */
  185                 memcpy((void*)lastaddr,
  186                     shdr[symtabindex].sh_offset + kstart,
  187                     shdr[symtabindex].sh_size);
  188                 lastaddr += shdr[symtabindex].sh_size;
  189 
  190                 /* .strtab size */
  191                 tmp = shdr[symstrindex].sh_size;
  192                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  193                 lastaddr += sizeof(shdr[symstrindex].sh_size);
  194 
  195                 /* .strtab data */
  196                 memcpy((void*)lastaddr,
  197                     shdr[symstrindex].sh_offset + kstart,
  198                     shdr[symstrindex].sh_size);
  199         } else {
  200                 /* Do not take any chances */
  201                 tmp = 0;
  202                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  203         }
  204 
  205         return entry_point;
  206 }
  207 
  208 void
  209 _startC(register_t a0, register_t a1, register_t a2, register_t a3)
  210 {
  211         unsigned int * code;
  212         int i;
  213         void (*entry_point)(register_t, register_t, register_t, register_t);
  214 
  215         /* 
  216          * Relocate segment to the predefined memory location
  217          * Most likely it will be KSEG0/KSEG1 address
  218          */
  219         entry_point = load_kernel(kernel_start);
  220 
  221         /* Pass saved registers to original _start */
  222         entry_point(a0, a1, a2, a3);
  223 }

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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