loader/i386/multiboot_elfxx.c

   1 /*
   2  *  GRUB  --  GRand Unified Bootloader
   3  *  Copyright (C) 1999,2000,2001,2002,2003,2004,2005,2007,2008,2009  Free Software Foundation, Inc.
   4  *
   5  *  GRUB is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation, either version 3 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  GRUB is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #if defined(MULTIBOOT_LOAD_ELF32)
  20 # define XX             32
  21 # define E_MACHINE      EM_386
  22 # define ELFCLASSXX     ELFCLASS32
  23 # define Elf_Ehdr       Elf32_Ehdr
  24 # define Elf_Phdr       Elf32_Phdr
  25 #elif defined(MULTIBOOT_LOAD_ELF64)
  26 # define XX             64
  27 # define E_MACHINE      EM_X86_64
  28 # define ELFCLASSXX     ELFCLASS64
  29 # define Elf_Ehdr       Elf64_Ehdr
  30 # define Elf_Phdr       Elf64_Phdr
  31 #else
  32 #error "I'm confused"
  33 #endif
  34
  35 #define CONCAT(a,b)     CONCAT_(a, b)
  36 #define CONCAT_(a,b)    a ## b
  37
  38 /* Check if BUFFER contains ELF32 (or ELF64).  */
  39 static int
  40 CONCAT(grub_multiboot_is_elf, XX) (void *buffer)
  41 {
  42   Elf_Ehdr *ehdr = (Elf_Ehdr *) buffer;
  43
  44   return ehdr->e_ident[EI_CLASS] == ELFCLASSXX;
  45 }
  46
  47 static grub_err_t
  48 CONCAT(grub_multiboot_load_elf, XX) (grub_file_t file, void *buffer)
  49 {
  50   Elf_Ehdr *ehdr = (Elf_Ehdr *) buffer;
  51   char *phdr_base;
  52   int lowest_segment = -1, highest_segment = -1;
  53   int i;
  54
  55   if (ehdr->e_ident[EI_CLASS] != ELFCLASSXX)
  56     return grub_error (GRUB_ERR_UNKNOWN_OS, "invalid ELF class");
  57
  58   if (ehdr->e_ident[EI_MAG0] != ELFMAG0
  59       || ehdr->e_ident[EI_MAG1] != ELFMAG1
  60       || ehdr->e_ident[EI_MAG2] != ELFMAG2
  61       || ehdr->e_ident[EI_MAG3] != ELFMAG3
  62       || ehdr->e_version != EV_CURRENT
  63       || ehdr->e_ident[EI_DATA] != ELFDATA2LSB
  64       || ehdr->e_machine != E_MACHINE)
  65     return grub_error(GRUB_ERR_UNKNOWN_OS, "no valid ELF header found");
  66
  67   if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
  68     return grub_error (GRUB_ERR_UNKNOWN_OS, "invalid ELF file type");
  69
  70   /* FIXME: Should we support program headers at strange locations?  */
  71   if (ehdr->e_phoff + ehdr->e_phnum * ehdr->e_phentsize > MULTIBOOT_SEARCH)
  72     return grub_error (GRUB_ERR_BAD_OS, "program header at a too high offset");
  73
  74 #ifdef MULTIBOOT_LOAD_ELF64
  75   /* We still in 32-bit mode.  */
  76   if (ehdr->e_entry > 0xffffffff)
  77     return grub_error (GRUB_ERR_BAD_OS, "invalid entry point for ELF64");
  78 #endif
  79
  80   phdr_base = (char *) buffer + ehdr->e_phoff;
  81 #define phdr(i)                 ((Elf_Phdr *) (phdr_base + (i) * ehdr->e_phentsize))
  82
  83   for (i = 0; i < ehdr->e_phnum; i++)
  84     if (phdr(i)->p_type == PT_LOAD && phdr(i)->p_filesz != 0)
  85       {
  86         /* Beware that segment 0 isn't necessarily loadable */
  87         if (lowest_segment == -1
  88             || phdr(i)->p_paddr < phdr(lowest_segment)->p_paddr)
  89           lowest_segment = i;
  90         if (highest_segment == -1
  91             || phdr(i)->p_paddr > phdr(highest_segment)->p_paddr)
  92           highest_segment = i;
  93       }
  94
  95   if (lowest_segment == -1)
  96     return grub_error (GRUB_ERR_BAD_OS, "ELF contains no loadable segments");
  97
  98   code_size = (phdr(highest_segment)->p_paddr + phdr(highest_segment)->p_memsz) - phdr(lowest_segment)->p_paddr;
  99   grub_multiboot_payload_dest = phdr(lowest_segment)->p_paddr;
 100
 101   grub_multiboot_payload_size += code_size;
 102   playground = grub_malloc (RELOCATOR_SIZEOF(forward) + grub_multiboot_payload_size + RELOCATOR_SIZEOF(backward));
 103   if (! playground)
 104     return grub_errno;
 105
 106   grub_multiboot_payload_orig = (long) playground + RELOCATOR_SIZEOF(forward);
 107
 108   /* Load every loadable segment in memory.  */
 109   for (i = 0; i < ehdr->e_phnum; i++)
 110     {
 111       if (phdr(i)->p_type == PT_LOAD && phdr(i)->p_filesz != 0)
 112         {
 113           char *load_this_module_at = (char *) (grub_multiboot_payload_orig + (long) (phdr(i)->p_paddr - phdr(lowest_segment)->p_paddr));
 114
 115           grub_dprintf ("multiboot_loader", "segment %d: paddr=0x%lx, memsz=0x%lx, vaddr=0x%lx\n",
 116                         i, (long) phdr(i)->p_paddr, (long) phdr(i)->p_memsz, (long) phdr(i)->p_vaddr);
 117
 118           if (grub_file_seek (file, (grub_off_t) phdr(i)->p_offset)
 119               == (grub_off_t) -1)
 120             return grub_error (GRUB_ERR_BAD_OS,
 121                                "invalid offset in program header");
 122
 123           if (grub_file_read (file, load_this_module_at, phdr(i)->p_filesz)
 124               != (grub_ssize_t) phdr(i)->p_filesz)
 125             return grub_error (GRUB_ERR_BAD_OS,
 126                                "couldn't read segment from file");
 127
 128           if (phdr(i)->p_filesz < phdr(i)->p_memsz)
 129             grub_memset (load_this_module_at + phdr(i)->p_filesz, 0,
 130                          phdr(i)->p_memsz - phdr(i)->p_filesz);
 131         }
 132     }
 133
 134   for (i = 0; i < ehdr->e_phnum; i++)
 135     if (phdr(i)->p_vaddr <= ehdr->e_entry
 136         && phdr(i)->p_vaddr + phdr(i)->p_memsz > ehdr->e_entry)
 137       {
 138         grub_multiboot_payload_entry_offset = (ehdr->e_entry - phdr(i)->p_vaddr)
 139           + (phdr(i)->p_paddr  - phdr(lowest_segment)->p_paddr);
 140         break;
 141       }
 142
 143   if (i == ehdr->e_phnum)
 144     return grub_error (GRUB_ERR_BAD_OS, "entry point isn't in a segment");
 145
 146 #undef phdr
 147
 148   return grub_errno;
 149 }
 150
 151 #undef XX
 152 #undef E_MACHINE
 153 #undef ELFCLASSXX
 154 #undef Elf_Ehdr
 155 #undef Elf_Phdr