diff mbox series

[02/10] backtrace: Implement on top of <unwind-link.h>

Message ID 5d751702e5e7ff0f502b447a0206326396e8be0b.1613577607.git.fweimer@redhat.com
State New
Headers show
Series Unwinder interface consolidation | expand

Commit Message

Florian Weimer Feb. 17, 2021, 4:02 p.m. UTC 
This reimplements the generic version of backtrace.
---
 debug/backtrace.c | 84 ++++++++++-------------------------------------
 1 file changed, 17 insertions(+), 67 deletions(-)

Comments

Carlos O'Donell March 1, 2021, 1:54 p.m. UTC | #1 
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
>
diff mbox series

Patch

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;
   _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