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 FILE_LICENCE ( GPL2_OR_LATER );
20
21 /**
22 * @file
23 *
24 * ELF image format
25 *
26 * A "pure" ELF image is not a bootable image. There are various
27 * bootable formats based upon ELF (e.g. Multiboot), which share
28 * common ELF-related functionality.
29 */
30
31 #include <errno.h>
32 #include <elf.h>
33 #include <gpxe/uaccess.h>
34 #include <gpxe/segment.h>
35 #include <gpxe/image.h>
36 #include <gpxe/elf.h>
37
38 typedef Elf32_Ehdr Elf_Ehdr;
39 typedef Elf32_Phdr Elf_Phdr;
40 typedef Elf32_Off Elf_Off;
41
42 /**
43 * Load ELF segment into memory
44 *
45 * @v image ELF file
46 * @v phdr ELF program header
47 * @v ehdr ELF executable header
48 * @ret rc Return status code
49 */
elf_load_segment(struct image * image,Elf_Phdr * phdr,Elf_Ehdr * ehdr)50 static int elf_load_segment ( struct image *image, Elf_Phdr *phdr,
51 Elf_Ehdr *ehdr ) {
52 physaddr_t dest;
53 userptr_t buffer;
54 unsigned long e_offset;
55 int rc;
56
57 /* Do nothing for non-PT_LOAD segments */
58 if ( phdr->p_type != PT_LOAD )
59 return 0;
60
61 /* Check segment lies within image */
62 if ( ( phdr->p_offset + phdr->p_filesz ) > image->len ) {
63 DBGC ( image, "ELF %p segment outside image\n", image );
64 return -ENOEXEC;
65 }
66
67 /* Find start address: use physical address for preference,
68 * fall back to virtual address if no physical address
69 * supplied.
70 */
71 dest = phdr->p_paddr;
72 if ( ! dest )
73 dest = phdr->p_vaddr;
74 if ( ! dest ) {
75 DBGC ( image, "ELF %p segment loads to physical address 0\n",
76 image );
77 return -ENOEXEC;
78 }
79 buffer = phys_to_user ( dest );
80
81 DBGC ( image, "ELF %p loading segment [%x,%x) to [%x,%x,%x)\n", image,
82 phdr->p_offset, ( phdr->p_offset + phdr->p_filesz ),
83 phdr->p_paddr, ( phdr->p_paddr + phdr->p_filesz ),
84 ( phdr->p_paddr + phdr->p_memsz ) );
85
86 /* Verify and prepare segment */
87 if ( ( rc = prep_segment ( buffer, phdr->p_filesz,
88 phdr->p_memsz ) ) != 0 ) {
89 DBGC ( image, "ELF %p could not prepare segment: %s\n",
90 image, strerror ( rc ) );
91 return rc;
92 }
93
94 /* Copy image to segment */
95 memcpy_user ( buffer, 0, image->data, phdr->p_offset, phdr->p_filesz );
96
97 /* Set execution address, if it lies within this segment */
98 if ( ( e_offset = ( ehdr->e_entry - dest ) ) < phdr->p_filesz ) {
99 image->priv.phys = ehdr->e_entry;
100 DBGC ( image, "ELF %p found physical entry point at %lx\n",
101 image, image->priv.phys );
102 } else if ( ( e_offset = ( ehdr->e_entry - phdr->p_vaddr ) )
103 < phdr->p_filesz ) {
104 if ( ! image->priv.phys ) {
105 image->priv.phys = ( dest + e_offset );
106 DBGC ( image, "ELF %p found virtual entry point at %lx"
107 " (virt %lx)\n", image, image->priv.phys,
108 ( ( unsigned long ) ehdr->e_entry ) );
109 }
110 }
111
112 return 0;
113 }
114
115 /**
116 * Load ELF image into memory
117 *
118 * @v image ELF file
119 * @ret rc Return status code
120 */
elf_load(struct image * image)121 int elf_load ( struct image *image ) {
122 Elf_Ehdr ehdr;
123 Elf_Phdr phdr;
124 Elf_Off phoff;
125 unsigned int phnum;
126 int rc;
127
128 /* Image type must already have been set by caller */
129 assert ( image->type != NULL );
130
131 /* Read ELF header */
132 copy_from_user ( &ehdr, image->data, 0, sizeof ( ehdr ) );
133 if ( memcmp ( &ehdr.e_ident[EI_MAG0], ELFMAG, SELFMAG ) != 0 ) {
134 DBGC ( image, "ELF %p has invalid signature\n", image );
135 return -ENOEXEC;
136 }
137
138 /* Invalidate execution address */
139 image->priv.phys = 0;
140
141 /* Read ELF program headers */
142 for ( phoff = ehdr.e_phoff , phnum = ehdr.e_phnum ; phnum ;
143 phoff += ehdr.e_phentsize, phnum-- ) {
144 if ( phoff > image->len ) {
145 DBGC ( image, "ELF %p program header %d outside "
146 "image\n", image, phnum );
147 return -ENOEXEC;
148 }
149 copy_from_user ( &phdr, image->data, phoff, sizeof ( phdr ) );
150 if ( ( rc = elf_load_segment ( image, &phdr, &ehdr ) ) != 0 )
151 return rc;
152 }
153
154 /* Check for a valid execution address */
155 if ( ! image->priv.phys ) {
156 DBGC ( image, "ELF %p entry point %lx outside image\n",
157 image, ( ( unsigned long ) ehdr.e_entry ) );
158 return -ENOEXEC;
159 }
160
161 return 0;
162 }
163