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/*
* Post-process a vdso elf image for inclusion into qemu.
*
* Copyright 2023 Linaro, Ltd.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include <stdlib.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <endian.h>
#include <unistd.h>
#include "elf.h"
#define bswap_(p) _Generic(*(p), \
uint16_t: __builtin_bswap16, \
uint32_t: __builtin_bswap32, \
uint64_t: __builtin_bswap64, \
int16_t: __builtin_bswap16, \
int32_t: __builtin_bswap32, \
int64_t: __builtin_bswap64)
#define bswaps(p) (*(p) = bswap_(p)(*(p)))
static void output_reloc(FILE *outf, void *buf, void *loc)
{
fprintf(outf, " 0x%08tx,\n", loc - buf);
}
static const char *sigreturn_sym;
static const char *rt_sigreturn_sym;
static unsigned sigreturn_addr;
static unsigned rt_sigreturn_addr;
#define N 32
#define elfN(x) elf32_##x
#define ElfN(x) Elf32_##x
#include "gen-vdso-elfn.c.inc"
#undef N
#undef elfN
#undef ElfN
#define N 64
#define elfN(x) elf64_##x
#define ElfN(x) Elf64_##x
#include "gen-vdso-elfn.c.inc"
#undef N
#undef elfN
#undef ElfN
int main(int argc, char **argv)
{
FILE *inf, *outf;
long total_len;
const char *prefix = "vdso";
const char *inf_name;
const char *outf_name = NULL;
unsigned char *buf;
bool need_bswap;
while (1) {
int opt = getopt(argc, argv, "o:p:r:s:");
if (opt < 0) {
break;
}
switch (opt) {
case 'o':
outf_name = optarg;
break;
case 'p':
prefix = optarg;
break;
case 'r':
rt_sigreturn_sym = optarg;
break;
case 's':
sigreturn_sym = optarg;
break;
default:
usage:
fprintf(stderr, "usage: [-p prefix] [-r rt-sigreturn-name] "
"[-s sigreturn-name] -o output-file input-file\n");
return EXIT_FAILURE;
}
}
if (optind >= argc || outf_name == NULL) {
goto usage;
}
inf_name = argv[optind];
/*
* Open the input and output files.
*/
inf = fopen(inf_name, "rb");
if (inf == NULL) {
goto perror_inf;
}
outf = fopen(outf_name, "w");
if (outf == NULL) {
goto perror_outf;
}
/*
* Read the input file into a buffer.
* We expect the vdso to be small, on the order of one page,
* therefore we do not expect a partial read.
*/
fseek(inf, 0, SEEK_END);
total_len = ftell(inf);
fseek(inf, 0, SEEK_SET);
buf = malloc(total_len);
if (buf == NULL) {
goto perror_inf;
}
errno = 0;
if (fread(buf, 1, total_len, inf) != total_len) {
if (errno) {
goto perror_inf;
}
fprintf(stderr, "%s: incomplete read\n", inf_name);
return EXIT_FAILURE;
}
fclose(inf);
/*
* Write out the vdso image now, before we make local changes.
*/
fprintf(outf,
"/* Automatically generated from linux-user/gen-vdso.c. */\n"
"\n"
"static const uint8_t %s_image[] = {",
prefix);
for (long i = 0; i < total_len; ++i) {
if (i % 12 == 0) {
fputs("\n ", outf);
}
fprintf(outf, " 0x%02x,", buf[i]);
}
fprintf(outf, "\n};\n\n");
/*
* Identify which elf flavor we're processing.
* The first 16 bytes of the file are e_ident.
*/
if (buf[EI_MAG0] != ELFMAG0 || buf[EI_MAG1] != ELFMAG1 ||
buf[EI_MAG2] != ELFMAG2 || buf[EI_MAG3] != ELFMAG3) {
fprintf(stderr, "%s: not an elf file\n", inf_name);
return EXIT_FAILURE;
}
switch (buf[EI_DATA]) {
case ELFDATA2LSB:
need_bswap = BYTE_ORDER != LITTLE_ENDIAN;
break;
case ELFDATA2MSB:
need_bswap = BYTE_ORDER != BIG_ENDIAN;
break;
default:
fprintf(stderr, "%s: invalid elf EI_DATA (%u)\n",
inf_name, buf[EI_DATA]);
return EXIT_FAILURE;
}
/*
* We need to relocate the VDSO image. The one built into the kernel
* is built for a fixed address. The one we built for QEMU is not,
* since that requires close control of the guest address space.
*
* Output relocation addresses as we go.
*/
fprintf(outf, "static const unsigned %s_relocs[] = {\n", prefix);
switch (buf[EI_CLASS]) {
case ELFCLASS32:
elf32_process(outf, buf, need_bswap);
break;
case ELFCLASS64:
elf64_process(outf, buf, need_bswap);
break;
default:
fprintf(stderr, "%s: invalid elf EI_CLASS (%u)\n",
inf_name, buf[EI_CLASS]);
return EXIT_FAILURE;
}
fprintf(outf, "};\n\n"); /* end vdso_relocs. */
fprintf(outf, "static const VdsoImageInfo %s_image_info = {\n", prefix);
fprintf(outf, " .image = %s_image,\n", prefix);
fprintf(outf, " .relocs = %s_relocs,\n", prefix);
fprintf(outf, " .image_size = sizeof(%s_image),\n", prefix);
fprintf(outf, " .reloc_count = ARRAY_SIZE(%s_relocs),\n", prefix);
fprintf(outf, " .sigreturn_ofs = 0x%x,\n", sigreturn_addr);
fprintf(outf, " .rt_sigreturn_ofs = 0x%x,\n", rt_sigreturn_addr);
fprintf(outf, "};\n");
/*
* Everything should have gone well.
*/
if (fclose(outf)) {
goto perror_outf;
}
return EXIT_SUCCESS;
perror_inf:
perror(inf_name);
return EXIT_FAILURE;
perror_outf:
perror(outf_name);
return EXIT_FAILURE;
}
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