src/image/elf.c

   1 /*
   2  * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 /**
  20  * @file
  21  *
  22  * ELF image format
  23  *
  24  */
  25
  26 #include <errno.h>
  27 #include <elf.h>
  28 #include <gpxe/uaccess.h>
  29 #include <gpxe/segment.h>
  30 #include <gpxe/image.h>
  31 #include <gpxe/elf.h>
  32
  33 struct image_type elf_image_type __image_type ( PROBE_NORMAL );
  34
  35 typedef Elf32_Ehdr      Elf_Ehdr;
  36 typedef Elf32_Phdr      Elf_Phdr;
  37 typedef Elf32_Off       Elf_Off;
  38
  39 /**
  40  * Execute ELF image
  41  *
  42  * @v image             ELF file
  43  * @ret rc              Return status code
  44  */
  45 static int elf_exec ( struct image *image __unused ) {
  46         return -ENOTSUP;
  47 }
  48
  49 /**
  50  * Load ELF segment into memory
  51  *
  52  * @v image             ELF file
  53  * @v phdr              ELF program header
  54  * @ret rc              Return status code
  55  */
  56 static int elf_load_segment ( struct image *image, Elf_Phdr *phdr ) {
  57         physaddr_t dest;
  58         userptr_t buffer;
  59         int rc;
  60
  61         /* Do nothing for non-PT_LOAD segments */
  62         if ( phdr->p_type != PT_LOAD )
  63                 return 0;
  64
  65         /* Check segment lies within image */
  66         if ( ( phdr->p_offset + phdr->p_filesz ) > image->len ) {
  67                 DBG ( "ELF segment outside ELF file\n" );
  68                 return -ENOEXEC;
  69         }
  70
  71         /* Find start address: use physical address for preference,
  72          * fall back to virtual address if no physical address
  73          * supplied.
  74          */
  75         dest = phdr->p_paddr;
  76         if ( ! dest )
  77                 dest = phdr->p_vaddr;
  78         if ( ! dest ) {
  79                 DBG ( "ELF segment loads to physical address 0\n" );
  80                 return -ENOEXEC;
  81         }
  82         buffer = phys_to_user ( dest );
  83
  84         DBG ( "ELF loading segment [%lx,%lx) to [%lx,%lx,%lx)\n",
  85               phdr->p_offset, ( phdr->p_offset + phdr->p_filesz ),
  86               phdr->p_paddr, ( phdr->p_paddr + phdr->p_filesz ),
  87               ( phdr->p_paddr + phdr->p_memsz ) );
  88
  89         /* Verify and prepare segment */
  90         if ( ( rc = prep_segment ( buffer, phdr->p_filesz,
  91                                    phdr->p_memsz ) ) != 0 ) {
  92                 DBG ( "ELF could not prepare segment: %s\n", strerror ( rc ) );
  93                 return rc;
  94         }
  95
  96         /* Copy image to segment */
  97         memcpy_user ( buffer, 0, image->data, phdr->p_offset, phdr->p_filesz );
  98
  99         return 0;
 100 }
 101
 102 /**
 103  * Load ELF image into memory
 104  *
 105  * @v image             ELF file
 106  * @ret rc              Return status code
 107  */
 108 int elf_load ( struct image *image ) {
 109         Elf_Ehdr ehdr;
 110         Elf_Phdr phdr;
 111         Elf_Off phoff;
 112         unsigned int phnum;
 113         int rc;
 114
 115         /* Read ELF header */
 116         copy_from_user ( &ehdr, image->data, 0, sizeof ( ehdr ) );
 117         if ( memcmp ( &ehdr.e_ident[EI_MAG0], ELFMAG, SELFMAG ) != 0 ) {
 118                 DBG ( "Invalid ELF signature\n" );
 119                 return -ENOEXEC;
 120         }
 121
 122         /* This is an ELF image, valid or otherwise */
 123         if ( ! image->type )
 124                 image->type = &elf_image_type;
 125
 126         /* Read ELF program headers */
 127         for ( phoff = ehdr.e_phoff , phnum = ehdr.e_phnum ; phnum ;
 128               phoff += ehdr.e_phentsize, phnum-- ) {
 129                 if ( phoff > image->len ) {
 130                         DBG ( "ELF program header %d outside ELF image\n",
 131                               phnum );
 132                         return -ENOEXEC;
 133                 }
 134                 copy_from_user ( &phdr, image->data, phoff, sizeof ( phdr ) );
 135                 if ( ( rc = elf_load_segment ( image, &phdr ) ) != 0 )
 136                         return rc;
 137         }
 138
 139         /* Record execution entry point in image private data field */
 140         image->priv.phys = ehdr.e_entry;
 141
 142         return 0;
 143 }
 144
 145 /** ELF image type */
 146 struct image_type elf_image_type __image_type ( PROBE_NORMAL ) = {
 147         .name = "ELF",
 148         .load = elf_load,
 149         .exec = elf_exec,
 150 };