aboutsummaryrefslogtreecommitdiff
path: root/arch/arm/vdso/vdsomunge.c
blob: f6455273b2f8768a303db0ccc4a4e875df08eb71 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
/*
 * Copyright 2015 Mentor Graphics Corporation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; version 2 of the
 * License.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 * vdsomunge - Host program which produces a shared object
 * architecturally specified to be usable by both soft- and hard-float
 * programs.
 *
 * The Procedure Call Standard for the ARM Architecture (ARM IHI
 * 0042E) says:
 *
 *	6.4.1 VFP and Base Standard Compatibility
 *
 *	Code compiled for the VFP calling standard is compatible with
 *	the base standard (and vice-versa) if no floating-point or
 *	containerized vector arguments or results are used.
 *
 * And ELF for the ARM Architecture (ARM IHI 0044E) (Table 4-2) says:
 *
 *	If both EF_ARM_ABI_FLOAT_XXXX bits are clear, conformance to the
 *	base procedure-call standard is implied.
 *
 * The VDSO is built with -msoft-float, as with the rest of the ARM
 * kernel, and uses no floating point arguments or results.  The build
 * process will produce a shared object that may or may not have the
 * EF_ARM_ABI_FLOAT_SOFT flag set (it seems to depend on the binutils
 * version; binutils starting with 2.24 appears to set it).  The
 * EF_ARM_ABI_FLOAT_HARD flag should definitely not be set, and this
 * program will error out if it is.
 *
 * If the soft-float flag is set, this program clears it.  That's all
 * it does.
 */

#include <elf.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#define swab16(x) \
	((((x) & 0x00ff) << 8) | \
	 (((x) & 0xff00) >> 8))

#define swab32(x) \
	((((x) & 0x000000ff) << 24) | \
	 (((x) & 0x0000ff00) <<  8) | \
	 (((x) & 0x00ff0000) >>  8) | \
	 (((x) & 0xff000000) >> 24))

#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
#define HOST_ORDER ELFDATA2LSB
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
#define HOST_ORDER ELFDATA2MSB
#endif

/* Some of the ELF constants we'd like to use were added to <elf.h>
 * relatively recently.
 */
#ifndef EF_ARM_EABI_VER5
#define EF_ARM_EABI_VER5 0x05000000
#endif

#ifndef EF_ARM_ABI_FLOAT_SOFT
#define EF_ARM_ABI_FLOAT_SOFT 0x200
#endif

#ifndef EF_ARM_ABI_FLOAT_HARD
#define EF_ARM_ABI_FLOAT_HARD 0x400
#endif

static int failed;
static const char *argv0;
static const char *outfile;

static void fail(const char *fmt, ...)
{
	va_list ap;

	failed = 1;
	fprintf(stderr, "%s: ", argv0);
	va_start(ap, fmt);
	vfprintf(stderr, fmt, ap);
	va_end(ap);
	exit(EXIT_FAILURE);
}

static void cleanup(void)
{
	if (failed && outfile != NULL)
		unlink(outfile);
}

static Elf32_Word read_elf_word(Elf32_Word word, bool swap)
{
	return swap ? swab32(word) : word;
}

static Elf32_Half read_elf_half(Elf32_Half half, bool swap)
{
	return swap ? swab16(half) : half;
}

static void write_elf_word(Elf32_Word val, Elf32_Word *dst, bool swap)
{
	*dst = swap ? swab32(val) : val;
}

int main(int argc, char **argv)
{
	const Elf32_Ehdr *inhdr;
	bool clear_soft_float;
	const char *infile;
	Elf32_Word e_flags;
	const void *inbuf;
	struct stat stat;
	void *outbuf;
	bool swap;
	int outfd;
	int infd;

	atexit(cleanup);
	argv0 = argv[0];

	if (argc != 3)
		fail("Usage: %s [infile] [outfile]\n", argv[0]);

	infile = argv[1];
	outfile = argv[2];

	infd = open(infile, O_RDONLY);
	if (infd < 0)
		fail("Cannot open %s: %s\n", infile, strerror(errno));

	if (fstat(infd, &stat) != 0)
		fail("Failed stat for %s: %s\n", infile, strerror(errno));

	inbuf = mmap(NULL, stat.st_size, PROT_READ, MAP_PRIVATE, infd, 0);
	if (inbuf == MAP_FAILED)
		fail("Failed to map %s: %s\n", infile, strerror(errno));

	close(infd);

	inhdr = inbuf;

	if (memcmp(&inhdr->e_ident, ELFMAG, SELFMAG) != 0)
		fail("Not an ELF file\n");

	if (inhdr->e_ident[EI_CLASS] != ELFCLASS32)
		fail("Unsupported ELF class\n");

	swap = inhdr->e_ident[EI_DATA] != HOST_ORDER;

	if (read_elf_half(inhdr->e_type, swap) != ET_DYN)
		fail("Not a shared object\n");

	if (read_elf_half(inhdr->e_machine, swap) != EM_ARM)
		fail("Unsupported architecture %#x\n", inhdr->e_machine);

	e_flags = read_elf_word(inhdr->e_flags, swap);

	if (EF_ARM_EABI_VERSION(e_flags) != EF_ARM_EABI_VER5) {
		fail("Unsupported EABI version %#x\n",
		     EF_ARM_EABI_VERSION(e_flags));
	}

	if (e_flags & EF_ARM_ABI_FLOAT_HARD)
		fail("Unexpected hard-float flag set in e_flags\n");

	clear_soft_float = !!(e_flags & EF_ARM_ABI_FLOAT_SOFT);

	outfd = open(outfile, O_RDWR | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
	if (outfd < 0)
		fail("Cannot open %s: %s\n", outfile, strerror(errno));

	if (ftruncate(outfd, stat.st_size) != 0)
		fail("Cannot truncate %s: %s\n", outfile, strerror(errno));

	outbuf = mmap(NULL, stat.st_size, PROT_READ | PROT_WRITE, MAP_SHARED,
		      outfd, 0);
	if (outbuf == MAP_FAILED)
		fail("Failed to map %s: %s\n", outfile, strerror(errno));

	close(outfd);

	memcpy(outbuf, inbuf, stat.st_size);

	if (clear_soft_float) {
		Elf32_Ehdr *outhdr;

		outhdr = outbuf;
		e_flags &= ~EF_ARM_ABI_FLOAT_SOFT;
		write_elf_word(e_flags, &outhdr->e_flags, swap);
	}

	if (msync(outbuf, stat.st_size, MS_SYNC) != 0)
		fail("Failed to sync %s: %s\n", outfile, strerror(errno));

	return EXIT_SUCCESS;
}