1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright 2015 Mentor Graphics Corporation.
4 *
5 * vdsomunge - Host program which produces a shared object
6 * architecturally specified to be usable by both soft- and hard-float
7 * programs.
8 *
9 * The Procedure Call Standard for the ARM Architecture (ARM IHI
10 * 0042E) says:
11 *
12 *	6.4.1 VFP and Base Standard Compatibility
13 *
14 *	Code compiled for the VFP calling standard is compatible with
15 *	the base standard (and vice-versa) if no floating-point or
16 *	containerized vector arguments or results are used.
17 *
18 * And ELF for the ARM Architecture (ARM IHI 0044E) (Table 4-2) says:
19 *
20 *	If both EF_ARM_ABI_FLOAT_XXXX bits are clear, conformance to the
21 *	base procedure-call standard is implied.
22 *
23 * The VDSO is built with -msoft-float, as with the rest of the ARM
24 * kernel, and uses no floating point arguments or results.  The build
25 * process will produce a shared object that may or may not have the
26 * EF_ARM_ABI_FLOAT_SOFT flag set (it seems to depend on the binutils
27 * version; binutils starting with 2.24 appears to set it).  The
28 * EF_ARM_ABI_FLOAT_HARD flag should definitely not be set, and this
29 * program will error out if it is.
30 *
31 * If the soft-float flag is set, this program clears it.  That's all
32 * it does.
33 */
34
35#include <elf.h>
36#include <errno.h>
37#include <fcntl.h>
38#include <stdarg.h>
39#include <stdbool.h>
40#include <stdio.h>
41#include <stdlib.h>
42#include <string.h>
43#include <sys/mman.h>
44#include <sys/stat.h>
45#include <sys/types.h>
46#include <unistd.h>
47
48#define swab16(x) \
49	((((x) & 0x00ff) << 8) | \
50	 (((x) & 0xff00) >> 8))
51
52#define swab32(x) \
53	((((x) & 0x000000ff) << 24) | \
54	 (((x) & 0x0000ff00) <<  8) | \
55	 (((x) & 0x00ff0000) >>  8) | \
56	 (((x) & 0xff000000) >> 24))
57
58#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
59#define HOST_ORDER ELFDATA2LSB
60#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
61#define HOST_ORDER ELFDATA2MSB
62#endif
63
64/* Some of the ELF constants we'd like to use were added to <elf.h>
65 * relatively recently.
66 */
67#ifndef EF_ARM_EABI_VER5
68#define EF_ARM_EABI_VER5 0x05000000
69#endif
70
71#ifndef EF_ARM_ABI_FLOAT_SOFT
72#define EF_ARM_ABI_FLOAT_SOFT 0x200
73#endif
74
75#ifndef EF_ARM_ABI_FLOAT_HARD
76#define EF_ARM_ABI_FLOAT_HARD 0x400
77#endif
78
79static int failed;
80static const char *argv0;
81static const char *outfile;
82
83static void fail(const char *fmt, ...)
84{
85	va_list ap;
86
87	failed = 1;
88	fprintf(stderr, "%s: ", argv0);
89	va_start(ap, fmt);
90	vfprintf(stderr, fmt, ap);
91	va_end(ap);
92	exit(EXIT_FAILURE);
93}
94
95static void cleanup(void)
96{
97	if (failed && outfile != NULL)
98		unlink(outfile);
99}
100
101static Elf32_Word read_elf_word(Elf32_Word word, bool swap)
102{
103	return swap ? swab32(word) : word;
104}
105
106static Elf32_Half read_elf_half(Elf32_Half half, bool swap)
107{
108	return swap ? swab16(half) : half;
109}
110
111static void write_elf_word(Elf32_Word val, Elf32_Word *dst, bool swap)
112{
113	*dst = swap ? swab32(val) : val;
114}
115
116int main(int argc, char **argv)
117{
118	const Elf32_Ehdr *inhdr;
119	bool clear_soft_float;
120	const char *infile;
121	Elf32_Word e_flags;
122	const void *inbuf;
123	struct stat stat;
124	void *outbuf;
125	bool swap;
126	int outfd;
127	int infd;
128
129	atexit(cleanup);
130	argv0 = argv[0];
131
132	if (argc != 3)
133		fail("Usage: %s [infile] [outfile]\n", argv[0]);
134
135	infile = argv[1];
136	outfile = argv[2];
137
138	infd = open(infile, O_RDONLY);
139	if (infd < 0)
140		fail("Cannot open %s: %s\n", infile, strerror(errno));
141
142	if (fstat(infd, &stat) != 0)
143		fail("Failed stat for %s: %s\n", infile, strerror(errno));
144
145	inbuf = mmap(NULL, stat.st_size, PROT_READ, MAP_PRIVATE, infd, 0);
146	if (inbuf == MAP_FAILED)
147		fail("Failed to map %s: %s\n", infile, strerror(errno));
148
149	close(infd);
150
151	inhdr = inbuf;
152
153	if (memcmp(&inhdr->e_ident, ELFMAG, SELFMAG) != 0)
154		fail("Not an ELF file\n");
155
156	if (inhdr->e_ident[EI_CLASS] != ELFCLASS32)
157		fail("Unsupported ELF class\n");
158
159	swap = inhdr->e_ident[EI_DATA] != HOST_ORDER;
160
161	if (read_elf_half(inhdr->e_type, swap) != ET_DYN)
162		fail("Not a shared object\n");
163
164	if (read_elf_half(inhdr->e_machine, swap) != EM_ARM)
165		fail("Unsupported architecture %#x\n", inhdr->e_machine);
166
167	e_flags = read_elf_word(inhdr->e_flags, swap);
168
169	if (EF_ARM_EABI_VERSION(e_flags) != EF_ARM_EABI_VER5) {
170		fail("Unsupported EABI version %#x\n",
171		     EF_ARM_EABI_VERSION(e_flags));
172	}
173
174	if (e_flags & EF_ARM_ABI_FLOAT_HARD)
175		fail("Unexpected hard-float flag set in e_flags\n");
176
177	clear_soft_float = !!(e_flags & EF_ARM_ABI_FLOAT_SOFT);
178
179	outfd = open(outfile, O_RDWR | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
180	if (outfd < 0)
181		fail("Cannot open %s: %s\n", outfile, strerror(errno));
182
183	if (ftruncate(outfd, stat.st_size) != 0)
184		fail("Cannot truncate %s: %s\n", outfile, strerror(errno));
185
186	outbuf = mmap(NULL, stat.st_size, PROT_READ | PROT_WRITE, MAP_SHARED,
187		      outfd, 0);
188	if (outbuf == MAP_FAILED)
189		fail("Failed to map %s: %s\n", outfile, strerror(errno));
190
191	close(outfd);
192
193	memcpy(outbuf, inbuf, stat.st_size);
194
195	if (clear_soft_float) {
196		Elf32_Ehdr *outhdr;
197
198		outhdr = outbuf;
199		e_flags &= ~EF_ARM_ABI_FLOAT_SOFT;
200		write_elf_word(e_flags, &outhdr->e_flags, swap);
201	}
202
203	if (msync(outbuf, stat.st_size, MS_SYNC) != 0)
204		fail("Failed to sync %s: %s\n", outfile, strerror(errno));
205
206	return EXIT_SUCCESS;
207}
208