[02/10] backtrace: Implement on top of <unwind-link.h>
Commit Message
This reimplements the generic version of backtrace.
---
debug/backtrace.c | 84 ++++++++++-------------------------------------
1 file changed, 17 insertions(+), 67 deletions(-)
Comments
On 2/17/21 11:02 AM, Florian Weimer via Libc-alpha wrote:
> This reimplements the generic version of backtrace.
LGTM.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> ---
> debug/backtrace.c | 84 ++++++++++-------------------------------------
> 1 file changed, 17 insertions(+), 67 deletions(-)
>
> diff --git a/debug/backtrace.c b/debug/backtrace.c
> index 5ded57bfc4..187d911a0d 100644
> --- a/debug/backtrace.c
> +++ b/debug/backtrace.c
> @@ -17,10 +17,7 @@
> License along with the GNU C Library; if not, see
> <https://www.gnu.org/licenses/>. */
>
> -#include <libc-lock.h>
> -#include <dlfcn.h>
> #include <execinfo.h>
> -#include <gnu/lib-names.h>
> #include <stdlib.h>
> #include <unwind.h>
> #include <unwind-link.h>
> @@ -28,47 +25,12 @@
> struct trace_arg
> {
> void **array;
> + struct unwind_link *unwind_link;
OK. Loaded unwinder.
> _Unwind_Word cfa;
> int cnt;
> int size;
> };
>
> -#ifdef SHARED
> -static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
> -static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
> -static _Unwind_Word (*unwind_getcfa) (struct _Unwind_Context *);
> -static void *libgcc_handle;
> -
> -
> -/* Dummy version in case libgcc_s does not contain the real code. */
> -static _Unwind_Word
> -dummy_getcfa (struct _Unwind_Context *ctx __attribute__ ((unused)))
> -{
> - return 0;
> -}
> -
> -
> -static void
> -init (void)
> -{
> - libgcc_handle = __libc_dlopen (LIBGCC_S_SO);
> -
> - if (libgcc_handle == NULL)
> - return;
> -
> - unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");
> - unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP");
> - if (unwind_getip == NULL)
> - unwind_backtrace = NULL;
> - unwind_getcfa = (__libc_dlsym (libgcc_handle, "_Unwind_GetCFA")
> - ?: dummy_getcfa);
> -}
> -#else
> -# define unwind_backtrace _Unwind_Backtrace
> -# define unwind_getip _Unwind_GetIP
> -# define unwind_getcfa _Unwind_GetCFA
> -#endif
> -
> static _Unwind_Reason_Code
> backtrace_helper (struct _Unwind_Context *ctx, void *a)
> {
> @@ -78,14 +40,16 @@ backtrace_helper (struct _Unwind_Context *ctx, void *a)
> Skip it. */
> if (arg->cnt != -1)
> {
> - arg->array[arg->cnt] = (void *) unwind_getip (ctx);
> + arg->array[arg->cnt]
> + = (void *) UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetIP) (ctx);
> if (arg->cnt > 0)
> arg->array[arg->cnt]
> = unwind_arch_adjustment (arg->array[arg->cnt - 1],
> arg->array[arg->cnt]);
>
> /* Check whether we make any progress. */
> - _Unwind_Word cfa = unwind_getcfa (ctx);
> + _Unwind_Word cfa
> + = UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetCFA) (ctx);
>
> if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt]
> && cfa == arg->cfa)
> @@ -100,20 +64,20 @@ backtrace_helper (struct _Unwind_Context *ctx, void *a)
> int
> __backtrace (void **array, int size)
> {
> - struct trace_arg arg = { .array = array, .cfa = 0, .size = size, .cnt = -1 };
> -
> - if (size <= 0)
> - return 0;
> -
> -#ifdef SHARED
> - __libc_once_define (static, once);
> -
> - __libc_once (once, init);
> - if (unwind_backtrace == NULL)
> + struct trace_arg arg =
> + {
> + .array = array,
> + .unwind_link = __libc_unwind_link_get (),
> + .cfa = 0,
> + .size = size,
> + .cnt = -1
> + };
> +
> + if (size <= 0 || arg.unwind_link == NULL)
> return 0;
> -#endif
>
> - unwind_backtrace (backtrace_helper, &arg);
> + UNWIND_LINK_PTR (arg.unwind_link, _Unwind_Backtrace)
> + (backtrace_helper, &arg);
>
> /* _Unwind_Backtrace seems to put NULL address above
> _start. Fix it up here. */
> @@ -123,17 +87,3 @@ __backtrace (void **array, int size)
> }
> weak_alias (__backtrace, backtrace)
> libc_hidden_def (__backtrace)
> -
> -
> -#ifdef SHARED
> -/* Free all resources if necessary. */
> -libc_freeres_fn (free_mem)
> -{
> - unwind_backtrace = NULL;
> - if (libgcc_handle != NULL)
> - {
> - __libc_dlclose (libgcc_handle);
> - libgcc_handle = NULL;
> - }
> -}
OK. Not needed because we handle the loaded libgcc in the unwind-link changes.
> -#endif
>
@@ -17,10 +17,7 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-#include <libc-lock.h>
-#include <dlfcn.h>
#include <execinfo.h>
-#include <gnu/lib-names.h>
#include <stdlib.h>
#include <unwind.h>
#include <unwind-link.h>
@@ -28,47 +25,12 @@
struct trace_arg
{
void **array;
+ struct unwind_link *unwind_link;
_Unwind_Word cfa;
int cnt;
int size;
};
-#ifdef SHARED
-static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
-static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
-static _Unwind_Word (*unwind_getcfa) (struct _Unwind_Context *);
-static void *libgcc_handle;
-
-
-/* Dummy version in case libgcc_s does not contain the real code. */
-static _Unwind_Word
-dummy_getcfa (struct _Unwind_Context *ctx __attribute__ ((unused)))
-{
- return 0;
-}
-
-
-static void
-init (void)
-{
- libgcc_handle = __libc_dlopen (LIBGCC_S_SO);
-
- if (libgcc_handle == NULL)
- return;
-
- unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");
- unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP");
- if (unwind_getip == NULL)
- unwind_backtrace = NULL;
- unwind_getcfa = (__libc_dlsym (libgcc_handle, "_Unwind_GetCFA")
- ?: dummy_getcfa);
-}
-#else
-# define unwind_backtrace _Unwind_Backtrace
-# define unwind_getip _Unwind_GetIP
-# define unwind_getcfa _Unwind_GetCFA
-#endif
-
static _Unwind_Reason_Code
backtrace_helper (struct _Unwind_Context *ctx, void *a)
{
@@ -78,14 +40,16 @@ backtrace_helper (struct _Unwind_Context *ctx, void *a)
Skip it. */
if (arg->cnt != -1)
{
- arg->array[arg->cnt] = (void *) unwind_getip (ctx);
+ arg->array[arg->cnt]
+ = (void *) UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetIP) (ctx);
if (arg->cnt > 0)
arg->array[arg->cnt]
= unwind_arch_adjustment (arg->array[arg->cnt - 1],
arg->array[arg->cnt]);
/* Check whether we make any progress. */
- _Unwind_Word cfa = unwind_getcfa (ctx);
+ _Unwind_Word cfa
+ = UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetCFA) (ctx);
if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt]
&& cfa == arg->cfa)
@@ -100,20 +64,20 @@ backtrace_helper (struct _Unwind_Context *ctx, void *a)
int
__backtrace (void **array, int size)
{
- struct trace_arg arg = { .array = array, .cfa = 0, .size = size, .cnt = -1 };
-
- if (size <= 0)
- return 0;
-
-#ifdef SHARED
- __libc_once_define (static, once);
-
- __libc_once (once, init);
- if (unwind_backtrace == NULL)
+ struct trace_arg arg =
+ {
+ .array = array,
+ .unwind_link = __libc_unwind_link_get (),
+ .cfa = 0,
+ .size = size,
+ .cnt = -1
+ };
+
+ if (size <= 0 || arg.unwind_link == NULL)
return 0;
-#endif
- unwind_backtrace (backtrace_helper, &arg);
+ UNWIND_LINK_PTR (arg.unwind_link, _Unwind_Backtrace)
+ (backtrace_helper, &arg);
/* _Unwind_Backtrace seems to put NULL address above
_start. Fix it up here. */
@@ -123,17 +87,3 @@ __backtrace (void **array, int size)
}
weak_alias (__backtrace, backtrace)
libc_hidden_def (__backtrace)
-
-
-#ifdef SHARED
-/* Free all resources if necessary. */
-libc_freeres_fn (free_mem)
-{
- unwind_backtrace = NULL;
- if (libgcc_handle != NULL)
- {
- __libc_dlclose (libgcc_handle);
- libgcc_handle = NULL;
- }
-}
-#endif