[PATCH v3 11/16] Print backtrace in a signal-safe manner
Peter Hutterer
peter.hutterer at who-t.net
Thu May 10 23:24:25 PDT 2012
On Mon, Apr 16, 2012 at 11:14:28AM -0700, Chase Douglas wrote:
> Backtraces are often printed in signal context, such as when a segfault
> occurs.
>
> Signed-off-by: Chase Douglas <chase.douglas at canonical.com>
> ---
> os/backtrace.c | 49 +++++++++++++++++++++++++++++--------------------
> 1 files changed, 29 insertions(+), 20 deletions(-)
>
> diff --git a/os/backtrace.c b/os/backtrace.c
> index 81348f4..d41c3f3 100644
> --- a/os/backtrace.c
> +++ b/os/backtrace.c
> @@ -45,29 +45,37 @@ xorg_backtrace(void)
> int size, i;
> Dl_info info;
>
> - ErrorF("\n");
> - ErrorF("Backtrace:\n");
> + ErrorSigSafe("\n");
> + ErrorSigSafe("Backtrace:\n");
> size = backtrace(array, 64);
is backtrace() itself signal-safe? the man pages suggest not yet it appears
to have worked well so far.
This commit should also be moved forward - it should go in before the
BUG_WARN updates
Cheers,
Peter
> for (i = 0; i < size; i++) {
> int rc = dladdr(array[i], &info);
>
> if (rc == 0) {
> - ErrorF("%d: ?? [%p]\n", i, array[i]);
> + ErrorSigSafe("%u: ?? [%p]\n", i, array[i]);
> continue;
> }
> mod = (info.dli_fname && *info.dli_fname) ? info.dli_fname : "(vdso)";
> if (info.dli_saddr)
> - ErrorF("%d: %s (%s+0x%lx) [%p]\n", i, mod,
> - info.dli_sname,
> - (long unsigned int) ((char *) array[i] -
> - (char *) info.dli_saddr), array[i]);
> + ErrorSigSafe(
> + "%u: %s (%s+0x%x) [%p]\n",
> + i,
> + mod,
> + info.dli_sname,
> + (long unsigned int)((char *) array[i] -
> + (char *) info.dli_saddr),
> + array[i]);
> else
> - ErrorF("%d: %s (%p+0x%lx) [%p]\n", i, mod,
> - info.dli_fbase,
> - (long unsigned int) ((char *) array[i] -
> - (char *) info.dli_fbase), array[i]);
> + ErrorSigSafe(
> + "%u: %s (%s+0x%x) [%p]\n",
> + i,
> + mod,
> + info.dli_fbase,
> + (long unsigned int)((char *) array[i] -
> + (char *) info.dli_fbase),
> + array[i]);
> }
> - ErrorF("\n");
> + ErrorSigSafe("\n");
> }
>
> #else /* not glibc or glibc < 2.1 */
> @@ -105,7 +113,7 @@ xorg_backtrace_frame(uintptr_t pc, int signo, void *arg)
> strcpy(signame, "unknown");
> }
>
> - ErrorF("** Signal %d (%s)\n", signo, signame);
> + ErrorSigSafe("** Signal %u (%s)\n", signo, signame);
> }
>
> snprintf(header, sizeof(header), "%d: 0x%lx", depth, pc);
> @@ -123,7 +131,8 @@ xorg_backtrace_frame(uintptr_t pc, int signo, void *arg)
> symname = "<section start>";
> offset = pc - (uintptr_t) dlinfo.dli_fbase;
> }
> - ErrorF("%s: %s:%s+0x%lx\n", header, dlinfo.dli_fname, symname, offset);
> + ErrorSigSafe("%s: %s:%s+0x%x\n", header, dlinfo.dli_fname, symname,
> + offset);
>
> }
> else {
> @@ -131,7 +140,7 @@ xorg_backtrace_frame(uintptr_t pc, int signo, void *arg)
> * probably poke elfloader here, but haven't written that code yet,
> * so we just print the pc.
> */
> - ErrorF("%s\n", header);
> + ErrorSigSafe("%s\n", header);
> }
>
> return 0;
> @@ -183,7 +192,7 @@ xorg_backtrace_pstack(void)
>
> if (bytesread > 0) {
> btline[bytesread] = 0;
> - ErrorF("%s", btline);
> + ErrorSigSafe("%s", btline);
> }
> else if ((bytesread < 0) || ((errno != EINTR) && (errno != EAGAIN)))
> done = 1;
> @@ -203,8 +212,8 @@ void
> xorg_backtrace(void)
> {
>
> - ErrorF("\n");
> - ErrorF("Backtrace:\n");
> + ErrorSigSafe("\n");
> + ErrorSigSafe("Backtrace:\n");
>
> #ifdef HAVE_PSTACK
> /* First try fork/exec of pstack - otherwise fall back to walkcontext
> @@ -221,9 +230,9 @@ xorg_backtrace(void)
> walkcontext(&u, xorg_backtrace_frame, &depth);
> else
> #endif
> - ErrorF("Failed to get backtrace info: %s\n", strerror(errno));
> + ErrorSigSafe("Failed to get backtrace info: %s\n", strerror(errno));
> }
> - ErrorF("\n");
> + ErrorSigSafe("\n");
> }
>
> #else
> --
> 1.7.9.1
>
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