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MINOR: debug: opportunistically load libthread_db.so.1 with set-dumpable=libs

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When loading libs into the core dump, let's also try to load
libthread_db.so.1 that gdb usually requires. It can significantly help
decoding the threads for systems which require it, and the file is quite
small. It can appear at a few different locations and is generally next
to libpthread.so, or alternately libc, so we first look where we found
them, and fall back to a few other common places. The file is really
small, a few tens of kB usually.
This commit is contained in:
Willy Tarreau 2026-03-18 11:17:22 +01:00
parent e07c9ee575
commit b93137ce67
1 changed files with 32 additions and 1 deletions
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33
src/tools.c
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@ -6038,6 +6038,7 @@ struct dl_collect_ctx {
size_t size;
char *prefix;
int pos;
char libpthread_path[PATH_MAX];
};
static int dl_collect_libs_cb(struct dl_phdr_info *info, size_t size, void *data)
@ -6066,6 +6067,18 @@ static int dl_collect_libs_cb(struct dl_phdr_info *info, size_t size, void *data
load_file_into_tar(&ctx->storage, &ctx->size, ctx->prefix, dbg, NULL, "haproxy-libs-dump");
}
/* check if we're loading libpthread or libc, and if so, keep a copy of its path */
if (!ctx->libpthread_path[0]) {
const char *basename = strrchr(fname, '/');
if (basename &&
(strncmp(basename, "/libpthread.so", 14) == 0 ||
strncmp(basename, "/libc.so", 8) == 0)) {
/* Note: this will trim the trailing slash */
strncpy(ctx->libpthread_path, fname,
MIN(basename - fname, sizeof(ctx->libpthread_path)));
}
}
leave:
/* increment the object's number */
ctx->pos++;
@ -6075,11 +6088,13 @@ static int dl_collect_libs_cb(struct dl_phdr_info *info, size_t size, void *data
/* dumps lib names and optionally address ranges */
void collect_libs(void)
{
struct dl_collect_ctx ctx = { .storage = NULL, .size = 0, .pos = 0 };
struct dl_collect_ctx ctx = { .storage = NULL, .size = 0, .pos = 0, .libpthread_path = "" };
const char *libthr_paths[] = { ctx.libpthread_path, "/usr/lib64", "/lib64", "/usr/lib", "/lib", NULL };
ulong pagesize = sysconf(_SC_PAGESIZE);
char dir_name[16];
size_t new_size;
void *page;
int i;
/* prepend a directory named after the starting pid */
snprintf(dir_name, sizeof(dir_name), "core-%u", getpid());
@ -6088,6 +6103,22 @@ void collect_libs(void)
/* callbacks will (re-)allocate ctx->storage */
dl_iterate_phdr(dl_collect_libs_cb, &ctx);
/* if we've found libpthread, there's likely a libthread_db.so.1 next
* to it, for use with gdb, and ctx.libpthread_path will point to it,
* and with it, libthr_paths[0]. Otherwise we search in a few other
* common paths.
*/
for (i = 0; libthr_paths[i]; i++) {
char path[PATH_MAX];
if (!*libthr_paths[i])
continue;
snprintf(path, sizeof(path), "%s/libthread_db.so.1", DISGUISE(libthr_paths[i]));
if (load_file_into_tar(&ctx.storage, &ctx.size, ctx.prefix, path, NULL, "haproxy-libs-dump") == 0)
break;
}
/* now that the archive is complete, we need to close it by appending
* two empty 512B blocks. We'll also place it aligned in an isolated
* mapped area so that it uses its own segment in a core dump for