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/*
* Extracts the libs archives from a core dump
*
* Copyright (C) 2026 Willy Tarreau <w@1wt.eu>
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
/* Note: builds with no option under glibc, and can be built as a minimal
* uploadable static executable using nolibc as well:
gcc -o libs-from-core -nostdinc -nostdlib -s -Os -static -fno-ident \
-fno-exceptions -fno-asynchronous-unwind-tables -fno-unwind-tables \
-Wl,--gc-sections,--orphan-handling=discard,-znoseparate-code \
-I /path/to/nolibc-sysroot/include libs-from-core.c
*/
#define _GNU_SOURCE
#include <sys/mman.h>
#include <sys/stat.h>
#include <elf.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
void usage(const char *progname)
{
const char *slash = strrchr(progname, '/');
if (slash)
progname = slash + 1;
fprintf(stderr,
"Usage: %s [-q] <core_file>\n"
"Locate a libs archive from an haproxy core dump and dump it to stdout.\n"
"Arguments:\n"
" -q Query mode: only report offset and length, do not dump\n"
" core_file Core dump produced by haproxy\n",
progname);
}
int main(int argc, char **argv)
{
Elf64_Ehdr *ehdr;
Elf64_Phdr *phdr;
struct stat st;
uint8_t *mem;
int i, fd;
const char *fname;
int quiet = 0;
int arg;
for (arg = 1; arg < argc; arg++) {
if (*argv[arg] != '-')
break;
if (strcmp(argv[arg], "-q") == 0)
quiet = 1;
else if (strcmp(argv[arg], "--") == 0) {
arg++;
break;
}
}
if (arg < argc) {
fname = argv[arg];
} else {
usage(argv[0]);
exit(1);
}
fd = open(fname, O_RDONLY);
/* Let's just map the core dump as an ELF header */
fstat(fd, &st);
mem = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
if (mem == MAP_FAILED) {
perror("mmap()");
exit(1);
}
/* get the program headers */
ehdr = (Elf64_Ehdr *)mem;
/* check that it's really a core. Should be "\x7fELF" */
if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0) {
fprintf(stderr, "ELF magic not found.\n");
exit(1);
}
if (ehdr->e_ident[EI_CLASS] != ELFCLASS64) {
fprintf(stderr, "Only 64-bit ELF supported.\n");
exit(1);
}
if (ehdr->e_type != ET_CORE) {
fprintf(stderr, "ELF type %d, not a core dump.\n", ehdr->e_type);
exit(1);
}
/* OK we can safely go with program headers */
phdr = (Elf64_Phdr *)(mem + ehdr->e_phoff);
for (i = 0; i < ehdr->e_phnum; i++) {
uint64_t size = phdr[i].p_filesz;
uint64_t offset = phdr[i].p_offset;
int ret = 0;
if (phdr[i].p_type != PT_LOAD)
continue;
//fprintf(stderr, "Scanning segment %d...\n", ehdr->e_phnum);
//fprintf(stderr, "\r%-5d: off=%lx va=%lx sz=%lx ", i, (long)offset, (long)phdr[i].p_vaddr, (long)size);
if (!size)
continue;
if (size < 512) // minimum for a tar header
continue;
/* tar magic */
if (memcmp(mem + offset + 257, "ustar\0""00", 8) != 0)
continue;
/* uid, gid */
if (memcmp(mem + offset + 108, "0000000\0""0000000\0", 16) != 0)
continue;
/* link name */
if (memcmp(mem + offset + 157, "haproxy-libs-dump\0", 18) != 0)
continue;
/* OK that's really it */
if (quiet)
printf("offset=%#lx size=%#lx\n", offset, size);
else
ret = (write(1, mem + offset, size) == size) ? 0 : 1;
return ret;
}
//fprintf(stderr, "\r%75s\n", "\r");
fprintf(stderr, "libs archive not found. Was 'set-dumpable' set to 'libs' ?\n");
return 1;
}
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