[03/10] arm: Implement backtrace on top of <unwind-link.h>

  ---
 sysdeps/arm/backtrace.c | 77 +++++++++++------------------------------
 1 file changed, 20 insertions(+), 57 deletions(-)
  

On 2/17/21 11:02 AM, Florian Weimer via Libc-alpha wrote:

LGTM. The arm version.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> ---
>  sysdeps/arm/backtrace.c | 77 +++++++++++------------------------------
>  1 file changed, 20 insertions(+), 57 deletions(-)
> 
> diff --git a/sysdeps/arm/backtrace.c b/sysdeps/arm/backtrace.c
> index 3ed975fb96..193f2410ba 100644
> --- a/sysdeps/arm/backtrace.c
> +++ b/sysdeps/arm/backtrace.c
> @@ -17,58 +17,36 @@
>     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 <stdlib.h>
> -#include <unwind.h>
> +#include <unwind-link.h>
>  
>  struct trace_arg
>  {
>    void **array;
> +  struct unwind_link *unwind_link;
>    int cnt, size;
>  };
>  
>  #ifdef SHARED
> -static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
> -static _Unwind_VRS_Result (*unwind_vrs_get) (_Unwind_Context *,
> -					     _Unwind_VRS_RegClass,
> -					     _uw,
> -					     _Unwind_VRS_DataRepresentation,
> -					     void *);
> -
> -static void *libgcc_handle;
> -
> -static void
> -init (void)
> -{
> -  libgcc_handle = __libc_dlopen ("libgcc_s.so.1");
> -
> -  if (libgcc_handle == NULL)
> -    return;
> -
> -  unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");
> -  unwind_vrs_get = __libc_dlsym (libgcc_handle, "_Unwind_VRS_Get");
> -  if (unwind_vrs_get == NULL)
> -    unwind_backtrace = NULL;
> -}
> -
>  /* This function is identical to "_Unwind_GetGR", except that it uses
>     "unwind_vrs_get" instead of "_Unwind_VRS_Get".  */
>  static inline _Unwind_Word
> -unwind_getgr (_Unwind_Context *context, int regno)
> +unwind_getgr (struct unwind_link *unwind_link,
> +	      _Unwind_Context *context, int regno)
>  {
>    _uw val;
> -  unwind_vrs_get (context, _UVRSC_CORE, regno, _UVRSD_UINT32, &val);
> +  UNWIND_LINK_PTR (unwind_link, _Unwind_VRS_Get)
> +    (context, _UVRSC_CORE, regno, _UVRSD_UINT32, &val);
>    return val;
>  }
>  
>  /* This macro is identical to the _Unwind_GetIP macro, except that it
>     uses "unwind_getgr" instead of "_Unwind_GetGR".  */
> -# define unwind_getip(context) \
> -  (unwind_getgr (context, 15) & ~(_Unwind_Word)1)
> -#else
> -# define unwind_backtrace _Unwind_Backtrace
> +#define unwind_getip(context) \
> +  (unwind_getgr (arg->unwind_link, context, 15) & ~(_Unwind_Word)1)
> +
> +#else /* !SHARED */
>  # define unwind_getip _Unwind_GetIP
>  #endif
>  
> @@ -89,20 +67,19 @@ backtrace_helper (struct _Unwind_Context *ctx, void *a)
>  int
>  __backtrace (void **array, int size)
>  {
> -  struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
> -
> -  if (size <= 0)
> -    return 0;
> -
> -#ifdef SHARED
> -  __libc_once_define (static, once);
> +  struct trace_arg arg =
> +    {
> +     .array = array,
> +     .unwind_link = __libc_unwind_link_get (),
> +     .size = size,
> +     .cnt = -1
> +    };
>  
> -  __libc_once (once, init);
> -  if (unwind_backtrace == NULL)
> +  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);
>  
>    if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
>      --arg.cnt;
> @@ -110,17 +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
>