The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/mips/mips/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: stable/8/sys/mips/mips/elf_trampoline.c 215938 2010-11-27 12:26:40Z jchandra $");
   27 #include <machine/asm.h>
   28 #include <sys/param.h>
   29 
   30 #ifdef __mips_n64
   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 #include "opt_kernname.h"
   46 
   47 extern char kernel_start[];
   48 extern char kernel_end[];
   49 
   50 static __inline void *
   51 memcpy(void *dst, const void *src, size_t len)
   52 {
   53         const char *s = src;
   54         char *d = dst;
   55 
   56         while (len) {
   57                 if (0 && len >= 4 && !((vm_offset_t)d & 3) &&
   58                     !((vm_offset_t)s & 3)) {
   59                         *(uint32_t *)d = *(uint32_t *)s;
   60                         s += 4;
   61                         d += 4;
   62                         len -= 4;
   63                 } else {
   64                         *d++ = *s++;
   65                         len--;
   66                 }
   67         }
   68         return (dst);
   69 }
   70 
   71 static __inline void
   72 bzero(void *addr, size_t count)
   73 {
   74         char *tmp = (char *)addr;
   75 
   76         while (count > 0) {
   77                 if (count >= 4 && !((vm_offset_t)tmp & 3)) {
   78                         *(uint32_t *)tmp = 0;
   79                         tmp += 4;
   80                         count -= 4;
   81                 } else {
   82                         *tmp = 0;
   83                         tmp++;
   84                         count--;
   85                 }
   86         }
   87 }
   88 
   89 /*
   90  * Relocate PT_LOAD segements of kernel ELF image to their respective
   91  * virtual addresses and return entry point
   92  */
   93 void *
   94 load_kernel(void * kstart)
   95 {
   96 #ifdef __mips_n64
   97         Elf64_Ehdr *eh;
   98         Elf64_Phdr phdr[64] /* XXX */;
   99         Elf64_Shdr shdr[64] /* XXX */;
  100 #else
  101         Elf32_Ehdr *eh;
  102         Elf32_Phdr phdr[64] /* XXX */;
  103         Elf32_Shdr shdr[64] /* XXX */;
  104 #endif
  105         int i, j;
  106         void *entry_point;
  107         vm_offset_t lastaddr = 0;
  108         int symtabindex = -1;
  109         int symstrindex = -1;
  110         
  111 #ifdef __mips_n64
  112         eh = (Elf64_Ehdr *)kstart;
  113 #else
  114         eh = (Elf32_Ehdr *)kstart;
  115 #endif
  116         entry_point = (void*)eh->e_entry;
  117         memcpy(phdr, (void *)(kstart + eh->e_phoff ),
  118             eh->e_phnum * sizeof(phdr[0]));
  119 
  120         memcpy(shdr, (void *)(kstart + eh->e_shoff),
  121             sizeof(*shdr) * eh->e_shnum);
  122 
  123         if (eh->e_shnum * eh->e_shentsize != 0 && eh->e_shoff != 0) {
  124                 for (i = 0; i < eh->e_shnum; i++) {
  125                         if (shdr[i].sh_type == SHT_SYMTAB) {
  126                                 /*
  127                                  * XXX: check if .symtab is in PT_LOAD?
  128                                  */
  129                                 if (shdr[i].sh_offset != 0 && 
  130                                     shdr[i].sh_size != 0) {
  131                                         symtabindex = i;
  132                                         symstrindex = shdr[i].sh_link;
  133                                 }
  134                         }
  135                 }
  136         }
  137 
  138         /*
  139          * Copy loadable segments
  140          */
  141         for (i = 0; i < eh->e_phnum; i++) {
  142                 volatile char c;
  143 
  144                 if (phdr[i].p_type != PT_LOAD)
  145                         continue;
  146                 
  147                 memcpy((void *)(phdr[i].p_vaddr),
  148                     (void*)(kstart + phdr[i].p_offset), phdr[i].p_filesz);
  149 
  150                 /* Clean space from oversized segments, eg: bss. */
  151                 if (phdr[i].p_filesz < phdr[i].p_memsz)
  152                         bzero((void *)(phdr[i].p_vaddr + phdr[i].p_filesz), 
  153                             phdr[i].p_memsz - phdr[i].p_filesz);
  154 
  155                 if (lastaddr < phdr[i].p_vaddr + phdr[i].p_memsz)
  156                         lastaddr = phdr[i].p_vaddr + phdr[i].p_memsz;
  157         }
  158 
  159         /* Now grab the symbol tables. */
  160         if (symtabindex >= 0 && symstrindex >= 0) {
  161                 *(Elf_Size *)lastaddr = SYMTAB_MAGIC;
  162                 lastaddr += sizeof(Elf_Size);
  163                 *(Elf_Size *)lastaddr = shdr[symtabindex].sh_size +
  164                     shdr[symstrindex].sh_size + 2*sizeof(Elf_Size);
  165                 lastaddr += sizeof(Elf_Size);
  166                 /* .symtab size */
  167                 *(Elf_Size *)lastaddr = shdr[symtabindex].sh_size;
  168                 lastaddr += sizeof(shdr[symtabindex].sh_size);
  169                 /* .symtab data */
  170                 memcpy((void*)lastaddr,
  171                     shdr[symtabindex].sh_offset + kstart,
  172                     shdr[symtabindex].sh_size);
  173                 lastaddr += shdr[symtabindex].sh_size;
  174 
  175                 /* .strtab size */
  176                 *(Elf_Size *)lastaddr = shdr[symstrindex].sh_size;
  177                 lastaddr += sizeof(shdr[symstrindex].sh_size);
  178 
  179                 /* .strtab data */
  180                 memcpy((void*)lastaddr,
  181                     shdr[symstrindex].sh_offset + kstart,
  182                     shdr[symstrindex].sh_size);
  183         } else
  184                 /* Do not take any chances */
  185                 *(Elf_Size *)lastaddr = 0;
  186 
  187         return entry_point;
  188 }
  189 
  190 void
  191 _startC(register_t a0, register_t a1, register_t a2, register_t a3)
  192 {
  193         unsigned int * code;
  194         int i;
  195         void (*entry_point)(register_t, register_t, register_t, register_t);
  196 
  197         /* 
  198          * Relocate segment to the predefined memory location
  199          * Most likely it will be KSEG0/KSEG1 address
  200          */
  201         entry_point = load_kernel(kernel_start);
  202 
  203         /* Pass saved registers to original _start */
  204         entry_point(a0, a1, a2, a3);
  205 }

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