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: releng/11.1/sys/mips/mips/elf_trampoline.c 256171 2013-10-09 00:22:21Z adrian $");
   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 
   36 /*
   37  * Since we are compiled outside of the normal kernel build process, we
   38  * need to include opt_global.h manually.
   39  */
   40 #include "opt_global.h"
   41 
   42 #include <sys/inflate.h>
   43 #include <machine/elf.h>
   44 #include <machine/cpufunc.h>
   45 #include <machine/stdarg.h>
   46 
   47 #ifndef KERNNAME
   48 #error Kernel name not provided
   49 #endif
   50 
   51 extern char kernel_start[];
   52 extern char kernel_end[];
   53 
   54 static __inline void *
   55 memcpy(void *dst, const void *src, size_t len)
   56 {
   57         const char *s = src;
   58         char *d = dst;
   59 
   60         while (len) {
   61                 if (0 && len >= 4 && !((vm_offset_t)d & 3) &&
   62                     !((vm_offset_t)s & 3)) {
   63                         *(uint32_t *)d = *(uint32_t *)s;
   64                         s += 4;
   65                         d += 4;
   66                         len -= 4;
   67                 } else {
   68                         *d++ = *s++;
   69                         len--;
   70                 }
   71         }
   72         return (dst);
   73 }
   74 
   75 static __inline void
   76 bzero(void *addr, size_t count)
   77 {
   78         char *tmp = (char *)addr;
   79 
   80         while (count > 0) {
   81                 if (count >= 4 && !((vm_offset_t)tmp & 3)) {
   82                         *(uint32_t *)tmp = 0;
   83                         tmp += 4;
   84                         count -= 4;
   85                 } else {
   86                         *tmp = 0;
   87                         tmp++;
   88                         count--;
   89                 }
   90         }
   91 }
   92 
   93 /*
   94  * Convert number to pointer, truncate on 64->32 case, sign extend
   95  * in 32->64 case
   96  */
   97 #define mkptr(x)        ((void *)(intptr_t)(int)(x))
   98 
   99 /*
  100  * Relocate PT_LOAD segements of kernel ELF image to their respective
  101  * virtual addresses and return entry point
  102  */
  103 void *
  104 load_kernel(void * kstart)
  105 {
  106 #if ELFSIZE == 64
  107         Elf64_Ehdr *eh;
  108         Elf64_Phdr phdr[64] /* XXX */;
  109         Elf64_Shdr shdr[64] /* XXX */;
  110 #else
  111         Elf32_Ehdr *eh;
  112         Elf32_Phdr phdr[64] /* XXX */;
  113         Elf32_Shdr shdr[64] /* XXX */;
  114 #endif
  115         int i, j;
  116         void *entry_point;
  117         vm_offset_t loadend = 0;
  118         intptr_t lastaddr;
  119         int symtabindex = -1;
  120         int symstrindex = -1;
  121         Elf_Size tmp;
  122         
  123 #if ELFSIZE == 64
  124         eh = (Elf64_Ehdr *)kstart;
  125 #else
  126         eh = (Elf32_Ehdr *)kstart;
  127 #endif
  128         entry_point = mkptr(eh->e_entry);
  129         memcpy(phdr, (void *)(kstart + eh->e_phoff),
  130             eh->e_phnum * sizeof(phdr[0]));
  131 
  132         memcpy(shdr, (void *)(kstart + eh->e_shoff),
  133             sizeof(*shdr) * eh->e_shnum);
  134 
  135         if (eh->e_shnum * eh->e_shentsize != 0 && eh->e_shoff != 0) {
  136                 for (i = 0; i < eh->e_shnum; i++) {
  137                         if (shdr[i].sh_type == SHT_SYMTAB) {
  138                                 /*
  139                                  * XXX: check if .symtab is in PT_LOAD?
  140                                  */
  141                                 if (shdr[i].sh_offset != 0 && 
  142                                     shdr[i].sh_size != 0) {
  143                                         symtabindex = i;
  144                                         symstrindex = shdr[i].sh_link;
  145                                 }
  146                         }
  147                 }
  148         }
  149 
  150         /*
  151          * Copy loadable segments
  152          */
  153         for (i = 0; i < eh->e_phnum; i++) {
  154                 volatile char c;
  155 
  156                 if (phdr[i].p_type != PT_LOAD)
  157                         continue;
  158                 
  159                 memcpy(mkptr(phdr[i].p_vaddr),
  160                     (void*)(kstart + phdr[i].p_offset), phdr[i].p_filesz);
  161 
  162                 /* Clean space from oversized segments, eg: bss. */
  163                 if (phdr[i].p_filesz < phdr[i].p_memsz)
  164                         bzero(mkptr(phdr[i].p_vaddr + phdr[i].p_filesz),
  165                             phdr[i].p_memsz - phdr[i].p_filesz);
  166 
  167                 if (loadend < phdr[i].p_vaddr + phdr[i].p_memsz)
  168                         loadend = phdr[i].p_vaddr + phdr[i].p_memsz;
  169         }
  170 
  171         /* Now grab the symbol tables. */
  172         lastaddr = (intptr_t)(int)loadend;
  173         if (symtabindex >= 0 && symstrindex >= 0) {
  174                 tmp = SYMTAB_MAGIC;
  175                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  176                 lastaddr += sizeof(Elf_Size);
  177                 tmp = shdr[symtabindex].sh_size +
  178                     shdr[symstrindex].sh_size + 2*sizeof(Elf_Size);
  179                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  180                 lastaddr += sizeof(Elf_Size);
  181                 /* .symtab size */
  182                 tmp = shdr[symtabindex].sh_size;
  183                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  184                 lastaddr += sizeof(shdr[symtabindex].sh_size);
  185                 /* .symtab data */
  186                 memcpy((void*)lastaddr,
  187                     shdr[symtabindex].sh_offset + kstart,
  188                     shdr[symtabindex].sh_size);
  189                 lastaddr += shdr[symtabindex].sh_size;
  190 
  191                 /* .strtab size */
  192                 tmp = shdr[symstrindex].sh_size;
  193                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  194                 lastaddr += sizeof(shdr[symstrindex].sh_size);
  195 
  196                 /* .strtab data */
  197                 memcpy((void*)lastaddr,
  198                     shdr[symstrindex].sh_offset + kstart,
  199                     shdr[symstrindex].sh_size);
  200         } else {
  201                 /* Do not take any chances */
  202                 tmp = 0;
  203                 memcpy((void *)lastaddr, &tmp, sizeof(tmp));
  204         }
  205 
  206         return entry_point;
  207 }
  208 
  209 void
  210 _startC(register_t a0, register_t a1, register_t a2, register_t a3)
  211 {
  212         unsigned int * code;
  213         int i;
  214         void (*entry_point)(register_t, register_t, register_t, register_t);
  215 
  216         /* 
  217          * Relocate segment to the predefined memory location
  218          * Most likely it will be KSEG0/KSEG1 address
  219          */
  220         entry_point = load_kernel(kernel_start);
  221 
  222         /* Pass saved registers to original _start */
  223         entry_point(a0, a1, a2, a3);
  224 }

Cache object: c219b1c4bd72602423ba6254d5421804


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