Use x86_64 backtrace as generic version.

No glibc configuration uses the present debug/backtrace.c, whereas
several #include the x86_64 version.  The x86_64 version is
effectively a generic one (using _Unwind_Backtrace from libgcc, which
works much more reliably than the built-in functions used by
debug/backtrace.c).  This patch moves it to debug/backtrace.c and
removes all the #includes of the x86_64 version from other
architectures which are no longer required.

I do not know whether all the other architecture-specific backtrace
implementations that are based on _Unwind_Backtrace are required, or
whether, where their differences from the generic version do something
useful, suitable hooks could be added to the generic version to reduce
the duplication involved.

Tested with build-many-glibcs.py that installed stripped shared
libraries are unchanged by this patch.

	* sysdeps/x86_64/backtrace.c: Move to ....
	* debug/backtrace.c: ... here.
	* sysdeps/aarch64/backtrace.c: Remove file.
	* sysdeps/alpha/backtrace.c: Likewise.
	* sysdeps/hppa/backtrace.c: Likewise.
	* sysdeps/ia64/backtrace.c: Likewise.
	* sysdeps/mips/backtrace.c: Likewise.
	* sysdeps/nios2/backtrace.c: Likewise.
	* sysdeps/riscv/backtrace.c: Likewise.
	* sysdeps/sh/backtrace.c: Likewise.
	* sysdeps/tile/backtrace.c: Likewise.

1 files changed, 0 insertions, 134 deletions

diff --git a/sysdeps/x86_64/backtrace.c b/sysdeps/x86_64/backtrace.c
deleted file mode 100644
index d423cc053a..0000000000
--- a/sysdeps/x86_64/backtrace.c
+++ /dev/null
@@ -1,134 +0,0 @@
-/* Return backtrace of current program state.
-   Copyright (C) 2003-2018 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://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>
-
-struct trace_arg
-{
-  void **array;
-  _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)
-{
-  struct trace_arg *arg = a;
-
-  /* We are first called with address in the __backtrace function.
-     Skip it.  */
-  if (arg->cnt != -1)
-    {
-      arg->array[arg->cnt] = (void *) unwind_getip (ctx);
-
-      /* Check whether we make any progress.  */
-      _Unwind_Word cfa = unwind_getcfa (ctx);
-
-      if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt]
-	 && cfa == arg->cfa)
-       return _URC_END_OF_STACK;
-      arg->cfa = cfa;
-    }
-  if (++arg->cnt == arg->size)
-    return _URC_END_OF_STACK;
-  return _URC_NO_REASON;
-}
-
-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)
-    return 0;
-#endif
-
-  unwind_backtrace (backtrace_helper, &arg);
-
-  /* _Unwind_Backtrace seems to put NULL address above
-     _start.  Fix it up here.  */
-  if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
-    --arg.cnt;
-  return arg.cnt != -1 ? arg.cnt : 0;
-}
-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