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 #include <grub/i386/relocator.h>
  36
  37 #define CONCAT(a,b)     CONCAT_(a, b)
  38 #define CONCAT_(a,b)    a ## b
  39
  40 /* Check if BUFFER contains ELF32 (or ELF64).  */
  41 static int
  42 CONCAT(grub_multiboot_is_elf, XX) (void *buffer)
  43 {
  44   Elf_Ehdr *ehdr = (Elf_Ehdr *) buffer;
  45
  46   return ehdr->e_ident[EI_CLASS] == ELFCLASSXX;
  47 }
  48
  49 static grub_err_t
  50 CONCAT(grub_multiboot_load_elf, XX) (grub_file_t file, void *buffer)
  51 {
  52   Elf_Ehdr *ehdr = (Elf_Ehdr *) buffer;
  53   char *phdr_base;
  54   int lowest_segment = -1, highest_segment = -1;
  55   int i;
  56
  57   if (ehdr->e_ident[EI_CLASS] != ELFCLASSXX)
  58     return grub_error (GRUB_ERR_UNKNOWN_OS, "invalid ELF class");
  59
  60   if (ehdr->e_ident[EI_MAG0] != ELFMAG0
  61       || ehdr->e_ident[EI_MAG1] != ELFMAG1
  62       || ehdr->e_ident[EI_MAG2] != ELFMAG2
  63       || ehdr->e_ident[EI_MAG3] != ELFMAG3
  64       || ehdr->e_version != EV_CURRENT
  65       || ehdr->e_ident[EI_DATA] != ELFDATA2LSB
  66       || ehdr->e_machine != E_MACHINE)
  67     return grub_error(GRUB_ERR_UNKNOWN_OS, "no valid ELF header found");
  68
  69   if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
  70     return grub_error (GRUB_ERR_UNKNOWN_OS, "invalid ELF file type");
  71
  72   /* FIXME: Should we support program headers at strange locations?  */
  73   if (ehdr->e_phoff + ehdr->e_phnum * ehdr->e_phentsize > MULTIBOOT_SEARCH)
  74     return grub_error (GRUB_ERR_BAD_OS, "program header at a too high offset");
  75
  76 #ifdef MULTIBOOT_LOAD_ELF64
  77   /* We still in 32-bit mode.  */
  78   if (ehdr->e_entry > 0xffffffff)
  79     return grub_error (GRUB_ERR_BAD_OS, "invalid entry point for ELF64");
  80 #endif
  81
  82   phdr_base = (char *) buffer + ehdr->e_phoff;
  83 #define phdr(i)                 ((Elf_Phdr *) (phdr_base + (i) * ehdr->e_phentsize))
  84
  85   for (i = 0; i < ehdr->e_phnum; i++)
  86     if (phdr(i)->p_type == PT_LOAD && phdr(i)->p_filesz != 0)
  87       {
  88         /* Beware that segment 0 isn't necessarily loadable */
  89         if (lowest_segment == -1
  90             || phdr(i)->p_paddr < phdr(lowest_segment)->p_paddr)
  91           lowest_segment = i;
  92         if (highest_segment == -1
  93             || phdr(i)->p_paddr > phdr(highest_segment)->p_paddr)
  94           highest_segment = i;
  95       }
  96
  97   if (lowest_segment == -1)
  98     return grub_error (GRUB_ERR_BAD_OS, "ELF contains no loadable segments");
  99
 100   code_size = (phdr(highest_segment)->p_paddr + phdr(highest_segment)->p_memsz) - phdr(lowest_segment)->p_paddr;
 101   grub_multiboot_payload_dest = phdr(lowest_segment)->p_paddr;
 102
 103   grub_multiboot_pure_size += code_size;
 104
 105   alloc_mbi = grub_multiboot_get_mbi_size ();
 106   grub_multiboot_payload_orig
 107     = grub_relocator32_alloc (grub_multiboot_pure_size + alloc_mbi + 65536);
 108
 109   if (!grub_multiboot_payload_orig)
 110     return grub_errno;
 111
 112   /* Load every loadable segment in memory.  */
 113   for (i = 0; i < ehdr->e_phnum; i++)
 114     {
 115       if (phdr(i)->p_type == PT_LOAD && phdr(i)->p_filesz != 0)
 116         {
 117           char *load_this_module_at = (char *) (grub_multiboot_payload_orig + (long) (phdr(i)->p_paddr - phdr(lowest_segment)->p_paddr));
 118
 119           grub_dprintf ("multiboot_loader", "segment %d: paddr=0x%lx, memsz=0x%lx, vaddr=0x%lx\n",
 120                         i, (long) phdr(i)->p_paddr, (long) phdr(i)->p_memsz, (long) phdr(i)->p_vaddr);
 121
 122           if (grub_file_seek (file, (grub_off_t) phdr(i)->p_offset)
 123               == (grub_off_t) -1)
 124             return grub_error (GRUB_ERR_BAD_OS,
 125                                "invalid offset in program header");
 126
 127           if (grub_file_read (file, load_this_module_at, phdr(i)->p_filesz)
 128               != (grub_ssize_t) phdr(i)->p_filesz)
 129             return grub_error (GRUB_ERR_BAD_OS,
 130                                "couldn't read segment from file");
 131
 132           if (phdr(i)->p_filesz < phdr(i)->p_memsz)
 133             grub_memset (load_this_module_at + phdr(i)->p_filesz, 0,
 134                          phdr(i)->p_memsz - phdr(i)->p_filesz);
 135         }
 136     }
 137
 138   for (i = 0; i < ehdr->e_phnum; i++)
 139     if (phdr(i)->p_vaddr <= ehdr->e_entry
 140         && phdr(i)->p_vaddr + phdr(i)->p_memsz > ehdr->e_entry)
 141       {
 142         grub_multiboot_payload_eip = grub_multiboot_payload_dest
 143           + (ehdr->e_entry - phdr(i)->p_vaddr) + (phdr(i)->p_paddr  - phdr(lowest_segment)->p_paddr);
 144         break;
 145       }
 146
 147   if (i == ehdr->e_phnum)
 148     return grub_error (GRUB_ERR_BAD_OS, "entry point isn't in a segment");
 149
 150 #undef phdr
 151
 152   return grub_errno;
 153 }
 154
 155 #undef XX
 156 #undef E_MACHINE
 157 #undef ELFCLASSXX
 158 #undef Elf_Ehdr
 159 #undef Elf_Phdr