[PATCH] os: use libunwind to generate backtraces

[Kristian Høgsberg]

On Sat, Feb 16, 2013 at 10:45 AM, Marcin Slusarz
<marcin.slusarz at gmail.com> wrote:
> Libunwind generates backtraces much more reliably than glibc's "backtrace".

Wow, didn't know about libunwind, it looks amazing.  Do you mind if
port this and use in weston?

Kristian

> Signed-off-by: Marcin Slusarz <marcin.slusarz at gmail.com>
> ---
>  configure.ac            |  7 +++++
>  include/dix-config.h.in |  3 +++
>  os/Makefile.am          |  5 ++++
>  os/backtrace.c          | 70 +++++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 85 insertions(+)
>
> diff --git a/configure.ac b/configure.ac
> index 9415a54..4a292da 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -309,6 +309,13 @@ AC_CHECK_HEADER([execinfo.h],[
>      ])]
>  )
>
> +PKG_CHECK_MODULES(LIBUNWIND, libunwind, [HAVE_LIBUNWIND=yes], [HAVE_LIBUNWIND=no])
> +if test "x$HAVE_LIBUNWIND" = xyes; then
> +       AC_DEFINE(HAVE_LIBUNWIND, 1, [Have libunwind support])
> +fi
> +AM_CONDITIONAL(HAVE_LIBUNWIND, [test "x$HAVE_LIBUNWIND" = xyes])
> +
> +
>  dnl ---------------------------------------------------------------------------
>  dnl Bus options and CPU capabilities.  Replaces logic in
>  dnl hw/xfree86/os-support/bus/Makefile.am, among others.
> diff --git a/include/dix-config.h.in b/include/dix-config.h.in
> index 578f249..5102263 100644
> --- a/include/dix-config.h.in
> +++ b/include/dix-config.h.in
> @@ -60,6 +60,9 @@
>  /* Has backtrace support */
>  #undef HAVE_BACKTRACE
>
> +/* Has libunwind support */
> +#undef HAVE_LIBUNWIND
> +
>  /* Define to 1 if you have the <byteswap.h> header file. */
>  #undef HAVE_BYTESWAP_H
>
> diff --git a/os/Makefile.am b/os/Makefile.am
> index 8891485..364b6da 100644
> --- a/os/Makefile.am
> +++ b/os/Makefile.am
> @@ -34,6 +34,11 @@ if XDMCP
>  libos_la_SOURCES += $(XDMCP_SRCS)
>  endif
>
> +if HAVE_LIBUNWIND
> +AM_CFLAGS += $(LIBUNWIND_CFLAGS)
> +libos_la_LIBADD += $(LIBUNWIND_LIBS)
> +endif
> +
>  EXTRA_DIST = $(SECURERPC_SRCS) $(XDMCP_SRCS)
>
>  if SPECIAL_DTRACE_OBJECTS
> diff --git a/os/backtrace.c b/os/backtrace.c
> index daac60c..02aeb03 100644
> --- a/os/backtrace.c
> +++ b/os/backtrace.c
> @@ -30,6 +30,75 @@
>  #include <errno.h>
>  #include <string.h>
>
> +#ifdef HAVE_LIBUNWIND
> +
> +#define UNW_LOCAL_ONLY
> +#include <libunwind.h>
> +
> +#ifndef _GNU_SOURCE
> +#define _GNU_SOURCE
> +#endif
> +#include <dlfcn.h>
> +
> +void
> +xorg_backtrace(void)
> +{
> +    unw_cursor_t cursor;
> +    unw_context_t context;
> +    unw_word_t off;
> +    unw_proc_info_t pip;
> +    int ret, i = 0;
> +    char procname[256];
> +    const char *filename;
> +    Dl_info dlinfo;
> +
> +    pip.unwind_info = NULL;
> +    ret = unw_getcontext(&context);
> +    if (ret) {
> +        ErrorFSigSafe("unw_getcontext: %d\n", ret);
> +        return;
> +    }
> +
> +    ret = unw_init_local(&cursor, &context);
> +    if (ret) {
> +        ErrorFSigSafe("unw_init_local: %d\n", ret);
> +        return;
> +    }
> +
> +    ErrorFSigSafe("\n");
> +    ErrorFSigSafe("Backtrace:\n");
> +    ret = unw_step(&cursor);
> +    while (ret > 0) {
> +        ret = unw_get_proc_info(&cursor, &pip);
> +        if (ret) {
> +            ErrorFSigSafe("unw_get_proc_info: %d\n", ret);
> +            break;
> +        }
> +
> +        ret = unw_get_proc_name(&cursor, procname, 256, &off);
> +        if (ret && ret != -UNW_ENOMEM) {
> +            if (ret != -UNW_EUNSPEC)
> +                ErrorFSigSafe("unw_get_proc_name: %d\n", ret);
> +            procname[0] = '?';
> +            procname[1] = 0;
> +        }
> +
> +        if (dladdr((void *)(pip.start_ip + off), &dlinfo) && dlinfo.dli_fname &&
> +                *dlinfo.dli_fname)
> +            filename = dlinfo.dli_fname;
> +        else
> +            filename = "?";
> +
> +        ErrorFSigSafe("%u: %s (%s%s+0x%x) [%p]\n", i++, filename, procname,
> +            ret == -UNW_ENOMEM ? "..." : "", (int)off, (void *)(pip.start_ip + off));
> +
> +        ret = unw_step(&cursor);
> +        if (ret < 0)
> +            ErrorFSigSafe("unw_step: %d\n", ret);
> +    }
> +    ErrorFSigSafe("\n");
> +}
> +#else
>  #ifdef HAVE_BACKTRACE
>  #ifndef _GNU_SOURCE
>  #define _GNU_SOURCE
> @@ -246,3 +315,4 @@ xorg_backtrace(void)
>
>  #endif
>  #endif
> +#endif
> --
> 1.8.1
>
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