Rockbox open source high quality audio player as a Music Player Daemon
mpris
rockbox
mpd
libadwaita
audio
rust
zig
deno
firmware: add simple ELF loader for static binaries
This is a small & simple ELF loader which just copies
program segments from disk to memory. It only supports
static binaries right now.
Change-Id: I8944feb5b9dafcc5c56e12383aed25e2718ad7ea
authored by
Aidan MacDonald
and committed by
Solomon Peachy
a610998e
21ba79d4
+466
+4
firmware/SOURCES
+4
firmware/SOURCES
+175
firmware/elf_loader.c
+175
firmware/elf_loader.c
···
1
+
/***************************************************************************
2
+
* __________ __ ___.
3
+
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
4
+
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
5
+
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
6
+
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
7
+
* \/ \/ \/ \/ \/
8
+
* $Id$
9
+
*
10
+
* Copyright (C) 2026 Aidan MacDonald
11
+
*
12
+
* This program is free software; you can redistribute it and/or
13
+
* modify it under the terms of the GNU General Public License
14
+
* as published by the Free Software Foundation; either version 2
15
+
* of the License, or (at your option) any later version.
16
+
*
17
+
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
18
+
* KIND, either express or implied.
19
+
*
20
+
****************************************************************************/
21
+
#include "elf_loader.h"
22
+
#include "elf-target.h"
23
+
#include "file.h"
24
+
25
+
#if defined(ROCKBOX_LITTLE_ENDIAN)
26
+
# define NATIVE_ELF_DATA ELFDATA2LSB
27
+
#elif defined(ROCKBOX_BIG_ENDIAN)
28
+
# define NATIVE_ELF_DATA ELFDATA2MSB
29
+
#else
30
+
# error "Unknown endianness!"
31
+
#endif
32
+
33
+
_Static_assert(TARGET_ELF_DATA == NATIVE_ELF_DATA,
34
+
"ELF binaries with foreign endianness not supported");
35
+
36
+
static int elf_validate_header(const struct elf_header *header)
37
+
{
38
+
if (header->ei_magic[0] != ELFMAG0 ||
39
+
header->ei_magic[1] != ELFMAG1 ||
40
+
header->ei_magic[2] != ELFMAG2 ||
41
+
header->ei_magic[3] != ELFMAG3)
42
+
return ELF_ERR_BADMAGIC;
43
+
44
+
if (header->ei_class != TARGET_ELF_CLASS ||
45
+
header->ei_data != TARGET_ELF_DATA)
46
+
return ELF_ERR_UNSUPP_ARCH;
47
+
48
+
if (header->ei_version != EV_CURRENT ||
49
+
header->e_version != EV_CURRENT)
50
+
return ELF_ERR_UNSUPP_VERSION;
51
+
52
+
if (header->ei_osabi != TARGET_ELF_OSABI ||
53
+
header->ei_abiversion != TARGET_ELF_ABIVERSION)
54
+
return ELF_ERR_UNSUPP_OS;
55
+
56
+
if (header->e_type != ET_EXEC)
57
+
return ELF_ERR_UNSUPP_TYPE;
58
+
59
+
if (header->e_machine != TARGET_ELF_MACHINE)
60
+
return ELF_ERR_UNSUPP_ARCH;
61
+
62
+
if (header->e_phoff == 0)
63
+
return ELF_ERR_EMPTY;
64
+
65
+
if (header->e_phentsize < sizeof(struct elf_phdr))
66
+
return ELF_ERR_UNSUPP_PHSIZE;
67
+
68
+
if (header->e_phnum == PN_XNUM)
69
+
return ELF_ERR_TOO_MANY_PHDRS;
70
+
71
+
return ELF_OK;
72
+
}
73
+
74
+
static int elf_validate_phdr(const struct elf_phdr *phdr,
75
+
const struct elf_load_context *ctx)
76
+
{
77
+
if (phdr->p_type != PT_LOAD)
78
+
return ELF_ERR_UNSUPP_PHDR;
79
+
80
+
if (phdr->p_filesz > phdr->p_memsz)
81
+
return ELF_ERR_INVALID_PHDR;
82
+
83
+
/* Ignore headers which occupy zero memory */
84
+
if (phdr->p_memsz == 0)
85
+
return 0;
86
+
87
+
for (size_t i = 0; i < ctx->num_mmap; ++i)
88
+
{
89
+
const struct elf_memory_map *entry = &ctx->mmap[i];
90
+
if (phdr->p_vaddr >= entry->addr &&
91
+
phdr->p_vaddr < entry->addr + entry->size &&
92
+
phdr->p_memsz <= entry->size)
93
+
{
94
+
if ((phdr->p_flags & entry->flags) != phdr->p_flags)
95
+
return ELF_ERR_MEM_INCOMPAT_FLAGS;
96
+
97
+
return ELF_OK;
98
+
}
99
+
}
100
+
101
+
return ELF_ERR_MEM_UNMAPPED;
102
+
}
103
+
104
+
int elf_loadfd(int fd,
105
+
const struct elf_load_context *ctx,
106
+
void **entrypoint)
107
+
{
108
+
struct elf_header ehdr;
109
+
struct elf_phdr phdr;
110
+
ssize_t nread;
111
+
int err;
112
+
113
+
nread = read(fd, &ehdr, sizeof(ehdr));
114
+
if (nread != (ssize_t)sizeof(ehdr))
115
+
return ELF_ERR_IO;
116
+
117
+
err = elf_validate_header(&ehdr);
118
+
if (err != ELF_OK)
119
+
return err;
120
+
121
+
/*
122
+
* Iterate over program headers, copying segments to memory
123
+
*/
124
+
for (size_t ph_index = 0; ph_index < ehdr.e_phnum; ++ph_index)
125
+
{
126
+
off_t ph_off = ehdr.e_phoff + (ph_index * ehdr.e_phentsize);
127
+
if (lseek(fd, ph_off, SEEK_SET) == (off_t)-1)
128
+
return ELF_ERR_IO;
129
+
130
+
nread = read(fd, &phdr, sizeof(phdr));
131
+
if (nread != (ssize_t)sizeof(phdr))
132
+
return ELF_ERR_IO;
133
+
134
+
err = elf_validate_phdr(&phdr, ctx);
135
+
if (err)
136
+
return err;
137
+
138
+
/* Load file data to memory if needed */
139
+
if (phdr.p_filesz > 0)
140
+
{
141
+
if (lseek(fd, phdr.p_offset, SEEK_SET) == (off_t)-1)
142
+
return ELF_ERR_IO;
143
+
144
+
nread = read(fd, (void *)phdr.p_vaddr, phdr.p_filesz);
145
+
if (nread < 0 || (uint32_t)nread != phdr.p_filesz)
146
+
return ELF_ERR_IO;
147
+
}
148
+
149
+
/* Zero out any memory not backed by file data */
150
+
if (phdr.p_memsz > phdr.p_filesz)
151
+
{
152
+
void *addr = (void *)phdr.p_vaddr + phdr.p_filesz;
153
+
size_t size = phdr.p_memsz - phdr.p_filesz;
154
+
155
+
memset(addr, 0, size);
156
+
}
157
+
}
158
+
159
+
*entrypoint = (void *)ehdr.e_entry;
160
+
return ELF_OK;
161
+
}
162
+
163
+
int elf_loadpath(const char *filename,
164
+
const struct elf_load_context *ctx,
165
+
void **entrypoint)
166
+
{
167
+
int fd = open(filename, O_RDONLY);
168
+
if (fd < 0)
169
+
return ELF_ERR_FILE_NOT_FOUND;
170
+
171
+
int err = elf_loadfd(fd, ctx, entrypoint);
172
+
173
+
close(fd);
174
+
return err;
175
+
}
+50
firmware/include/elf-target.h
+50
firmware/include/elf-target.h
···
1
+
/***************************************************************************
2
+
* __________ __ ___.
3
+
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
4
+
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
5
+
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
6
+
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
7
+
* \/ \/ \/ \/ \/
8
+
* $Id$
9
+
*
10
+
* Copyright (C) 2026 Aidan MacDonald
11
+
*
12
+
* This program is free software; you can redistribute it and/or
13
+
* modify it under the terms of the GNU General Public License
14
+
* as published by the Free Software Foundation; either version 2
15
+
* of the License, or (at your option) any later version.
16
+
*
17
+
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
18
+
* KIND, either express or implied.
19
+
*
20
+
****************************************************************************/
21
+
#ifndef __ELF_TARGET_H__
22
+
#define __ELF_TARGET_H__
23
+
24
+
#include "elf.h"
25
+
#include "config.h"
26
+
27
+
#define TARGET_ELF_CLASS ELFCLASS32
28
+
#define TARGET_ELF_OSABI ELFOSABI_SYSV
29
+
#define TARGET_ELF_ABIVERSION 0
30
+
#define elf_phdr elf32_phdr
31
+
32
+
#if defined(CPU_ARM)
33
+
# define TARGET_ELF_MACHINE EM_ARM
34
+
#elif defined(CPU_MIPS)
35
+
# define TARGET_ELF_MACHINE EM_MIPS
36
+
#elif defined(CPU_COLDFIRE)
37
+
# define TARGET_ELF_MACHINE EM_68K
38
+
#else
39
+
# error "Unknown CPU architecture!"
40
+
#endif
41
+
42
+
#if defined(ROCKBOX_LITTLE_ENDIAN)
43
+
# define TARGET_ELF_DATA ELFDATA2LSB
44
+
#elif defined(ROCKBOX_BIG_ENDIAN)
45
+
# define TARGET_ELF_DATA ELFDATA2MSB
46
+
#else
47
+
# error "Unknown endianness!"
48
+
#endif
49
+
50
+
#endif /* __ELF_TARGET_H__ */
+143
firmware/include/elf.h
+143
firmware/include/elf.h
···
1
+
/***************************************************************************
2
+
* __________ __ ___.
3
+
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
4
+
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
5
+
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
6
+
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
7
+
* \/ \/ \/ \/ \/
8
+
* $Id$
9
+
*
10
+
* Copyright (C) 2026 Aidan MacDonald
11
+
*
12
+
* This program is free software; you can redistribute it and/or
13
+
* modify it under the terms of the GNU General Public License
14
+
* as published by the Free Software Foundation; either version 2
15
+
* of the License, or (at your option) any later version.
16
+
*
17
+
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
18
+
* KIND, either express or implied.
19
+
*
20
+
****************************************************************************/
21
+
#ifndef __ELF_H__
22
+
#define __ELF_H__
23
+
24
+
#include <stdint.h>
25
+
26
+
/* Field offsets in the e_ident array */
27
+
#define EI_MAG0 0
28
+
#define EI_MAG1 1
29
+
#define EI_MAG2 2
30
+
#define EI_MAG3 3
31
+
#define EI_CLASS 4
32
+
#define EI_DATA 5
33
+
#define EI_VERSION 6
34
+
#define EI_OSABI 7
35
+
#define EI_ABIVERSION 8
36
+
#define EI_PAD 9
37
+
#define EI_NIDENT 16
38
+
39
+
/* Values for ei_magic */
40
+
#define ELFMAG0 0x7f
41
+
#define ELFMAG1 'E'
42
+
#define ELFMAG2 'L'
43
+
#define ELFMAG3 'F'
44
+
45
+
/* Values for ei_class */
46
+
#define ELFCLASSNONE 0
47
+
#define ELFCLASS32 1
48
+
#define ELFCLASS64 2
49
+
50
+
/* Values for ei_data */
51
+
#define ELFDATANONE 0
52
+
#define ELFDATA2LSB 1
53
+
#define ELFDATA2MSB 2
54
+
55
+
/* Values for ei_version and e_version */
56
+
#define EV_NONE 0
57
+
#define EV_CURRENT 1
58
+
59
+
/* Values for ei_osabi */
60
+
#define ELFOSABI_NONE ELFOSABI_SYSV
61
+
#define ELFOSABI_SYSV 0
62
+
63
+
/* Values for e_type */
64
+
#define ET_NONE 0
65
+
#define ET_REL 1
66
+
#define ET_EXEC 2
67
+
#define ET_DYN 3
68
+
#define ET_CORE 4
69
+
70
+
/* Values for e_machine */
71
+
#define EM_NONE 0
72
+
#define EM_68K 4
73
+
#define EM_MIPS 8
74
+
#define EM_ARM 40
75
+
76
+
/*
77
+
* Special value for e_phnum when the real number of
78
+
* program headers is too large.
79
+
*/
80
+
#define PN_XNUM 0xFFFFu
81
+
82
+
/* ELF basic types */
83
+
typedef uint32_t elf_addr_t;
84
+
typedef uint32_t elf_off_t;
85
+
86
+
/* ELF file header */
87
+
struct elf_header
88
+
{
89
+
union {
90
+
uint8_t e_ident[EI_NIDENT];
91
+
struct {
92
+
uint8_t ei_magic[4];
93
+
uint8_t ei_class;
94
+
uint8_t ei_data;
95
+
uint8_t ei_version;
96
+
uint8_t ei_osabi;
97
+
uint8_t ei_abiversion;
98
+
};
99
+
};
100
+
101
+
uint16_t e_type;
102
+
uint16_t e_machine;
103
+
uint32_t e_version;
104
+
elf_addr_t e_entry;
105
+
elf_off_t e_phoff;
106
+
elf_off_t e_shoff;
107
+
uint32_t e_flags;
108
+
uint16_t e_ehsize;
109
+
uint16_t e_phentsize;
110
+
uint16_t e_phnum;
111
+
uint16_t e_shentsize;
112
+
uint16_t e_shnum;
113
+
uint16_t e_shstrndx;
114
+
};
115
+
116
+
/* Values for p_type */
117
+
#define PT_NULL 0
118
+
#define PT_LOAD 1
119
+
#define PT_DYNAMIC 2
120
+
#define PT_INTERP 3
121
+
#define PT_NOTE 4
122
+
#define PT_SHLIB 5
123
+
#define PT_PHDR 6
124
+
125
+
/* Values for p_flags */
126
+
#define PF_X (1 << 0) /* Segment is executable */
127
+
#define PF_W (1 << 1) /* Segment is writable */
128
+
#define PF_R (1 << 2) /* Segment is readable */
129
+
130
+
/* ELF 32-bit program header */
131
+
struct elf32_phdr
132
+
{
133
+
uint32_t p_type;
134
+
elf_off_t p_offset;
135
+
elf_addr_t p_vaddr;
136
+
elf_addr_t p_paddr;
137
+
uint32_t p_filesz;
138
+
uint32_t p_memsz;
139
+
uint32_t p_flags;
140
+
uint32_t p_align;
141
+
};
142
+
143
+
#endif /* __ELF_H__ */
+94
firmware/include/elf_loader.h
+94
firmware/include/elf_loader.h
···
1
+
/***************************************************************************
2
+
* __________ __ ___.
3
+
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
4
+
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
5
+
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
6
+
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
7
+
* \/ \/ \/ \/ \/
8
+
* $Id$
9
+
*
10
+
* Copyright (C) 2026 Aidan MacDonald
11
+
*
12
+
* This program is free software; you can redistribute it and/or
13
+
* modify it under the terms of the GNU General Public License
14
+
* as published by the Free Software Foundation; either version 2
15
+
* of the License, or (at your option) any later version.
16
+
*
17
+
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
18
+
* KIND, either express or implied.
19
+
*
20
+
****************************************************************************/
21
+
#ifndef __ELF_LOADER_H__
22
+
#define __ELF_LOADER_H__
23
+
24
+
/*
25
+
* Primitive ELF loader -- allows loading an ELF binary from
26
+
* a file descriptor into RAM. Only static binaries linked at
27
+
* a fixed address are supported.
28
+
*
29
+
* The caller supplies a memory map which limits where the
30
+
* ELF file can be loaded; if a program header requests any
31
+
* memory outside of this mapping, loading will fail. There
32
+
* is no support for relocation, PIC code, or any form of
33
+
* dynamic linking.
34
+
*
35
+
* The loader can return the entry point of the ELF binary.
36
+
* It does not support arbitrary symbol lookups.
37
+
*/
38
+
39
+
#include <stdint.h>
40
+
#include <stddef.h>
41
+
42
+
enum elf_error
43
+
{
44
+
ELF_OK,
45
+
ELF_ERR_FILE_NOT_FOUND,
46
+
ELF_ERR_IO,
47
+
ELF_ERR_EMPTY,
48
+
ELF_ERR_BADMAGIC,
49
+
ELF_ERR_UNSUPP_ARCH,
50
+
ELF_ERR_UNSUPP_OS,
51
+
ELF_ERR_UNSUPP_VERSION,
52
+
ELF_ERR_UNSUPP_TYPE,
53
+
ELF_ERR_UNSUPP_FORMAT,
54
+
ELF_ERR_UNSUPP_PHSIZE,
55
+
ELF_ERR_TOO_MANY_PHDRS,
56
+
ELF_ERR_UNSUPP_PHDR,
57
+
ELF_ERR_INVALID_PHDR,
58
+
ELF_ERR_MEM_INCOMPAT_FLAGS,
59
+
ELF_ERR_MEM_UNMAPPED,
60
+
};
61
+
62
+
/*
63
+
* Describes an entry in the virtual memory map specified
64
+
* when loading an ELF file.
65
+
*
66
+
* ELF segments must fit completely within a single entry
67
+
* in the memory map. Segments crossing multiple mappings
68
+
* are rejected even if the mappings are contiguous.
69
+
*
70
+
* A segment may also be rejected if it has flags (R/W/X)
71
+
* not present in the corresponding memory map entry.
72
+
*/
73
+
struct elf_memory_map
74
+
{
75
+
uintptr_t addr;
76
+
size_t size;
77
+
uint32_t flags;
78
+
};
79
+
80
+
struct elf_load_context
81
+
{
82
+
const struct elf_memory_map *mmap;
83
+
size_t num_mmap;
84
+
};
85
+
86
+
int elf_loadfd(int fd,
87
+
const struct elf_load_context *ctx,
88
+
void **entrypoint);
89
+
90
+
int elf_loadpath(const char *filename,
91
+
const struct elf_load_context *ctx,
92
+
void **entrypoint);
93
+
94
+
#endif /* __ELF_LOADER_H__ */