Re: [PATCH 06/10] sparc: Implement backtrace on top <unwind-link.h>

[Carlos O'Donell <carlos@redhat.com>]

On 2/17/21 11:03 AM, Florian Weimer via Libc-alpha wrote:

LGTM. And the sparc version.

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

> ---
>  sysdeps/sparc/backtrace.c | 66 +++++++++------------------------------
>  1 file changed, 15 insertions(+), 51 deletions(-)
> 
> diff --git a/sysdeps/sparc/backtrace.c b/sysdeps/sparc/backtrace.c
> index 62196f0538..1bad755b7f 100644
> --- a/sysdeps/sparc/backtrace.c
> +++ b/sysdeps/sparc/backtrace.c
> @@ -21,9 +21,8 @@
>  #include <stddef.h>
>  #include <sysdep.h>
>  #include <sys/trap.h>
> -#include <dlfcn.h>
> -#include <unwind.h>
>  #include <backtrace.h>
> +#include <unwind-link.h>
>  
>  struct layout
>  {
> @@ -36,45 +35,12 @@ struct layout
>  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.1");
> -
> -  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)
>  {
> @@ -85,11 +51,12 @@ backtrace_helper (struct _Unwind_Context *ctx, void *a)
>       Skip it.  */
>    if (arg->cnt != -1)
>      {
> -      ip = unwind_getip (ctx);
> +      ip = UNWIND_LINK_PTR (arg->unwind_link, _Unwind_GetIP) (ctx);
>        arg->array[arg->cnt] = (void *) ip;
>  
>        /* 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)
> @@ -104,23 +71,19 @@ 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 };
> -  bool use_unwinder;
>    int count;
> +  struct trace_arg arg =
> +    {
> +     .array = array,
> +     .unwind_link = __libc_unwind_link_get (),
> +     .size = size,
> +     .cnt = -1,
> +    };
>  
>    if (size <= 0)
>      return 0;
>  
> -  use_unwinder = true;
> -#ifdef SHARED
> -  __libc_once_define (static, once);
> -
> -  __libc_once (once, init);
> -  if (unwind_backtrace == NULL)
> -    use_unwinder = false;
> -#endif
> -
> -  if (use_unwinder == false)
> +  if (arg.unwind_link == NULL)
>      {
>        struct layout *current;
>        unsigned long fp, i7;
> @@ -145,7 +108,8 @@ __backtrace (void **array, int size)
>      }
>    else
>      {
> -      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.  */
> 


-- 
Cheers,
Carlos.