[PATCH] Support backtrace () on IA-64, make it work even with -fomit-frame-pointer on AMD64

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

sysdeps/generic/backtrace.c doesn't work on IA-64 and with
-fomit-frame-pointer doesn't work on AMD64.
But all IA-64 code has .IA_64.unwind* and AMD64 uses
-fasynchronous-unwind-tables by default.
The following patch uses unwind info for backtrace instead
of stack frame walking by hand on these arches.

segfault.c will need similar treatment, but I don't think it is
good idea to duplicate the whole file.
Either the portion which records backtrace needs to be macroized,
such that sysdeps/ia64/segfault.c can use its own version,
or we could change backtrace's API such that e.g.
backtrace (NULL, size) would return number of frames which would
return the same value as backtrace (array, size), but without
storing anything into array, then segfault.c could do:
int cnt = backtrace (NULL, 65536);
arr = alloca (cnt * sizeof (void *));
cnt = backtrace (arr, cnt);

(or even INT_MAX instead of 65536, though limiting the backtrace
size IMHO makes sense).

2003-10-03  Jakub Jelinek  <jakub@redhat.com>

	* sysdeps/ia64/backtrace.c: New file.
	* sysdeps/x86_64/backtrace.c: New file.

--- libc/sysdeps/ia64/backtrace.c.jj	2003-10-03 14:36:36.000000000 +0200
+++ libc/sysdeps/ia64/backtrace.c	2003-10-03 14:52:09.000000000 +0200
@@ -0,0 +1,79 @@
+/* Return backtrace of current program state.
+   Copyright (C) 2003 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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <dlfcn.h>
+#include <execinfo.h>
+#include <stdlib.h>
+#include <unwind.h>
+
+struct trace_arg
+{
+  void **array;
+  int cnt, size;
+};
+
+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);
+  if (++arg->cnt == arg->size)
+    return _URC_END_OF_STACK;
+  return _URC_NO_REASON;
+}
+
+int
+__backtrace (array, size)
+     void **array;
+     int size;
+{
+  struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
+  static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
+
+  if (unwind_backtrace == NULL)
+    {
+      void *handle = __libc_dlopen ("libgcc_s.so.1");
+      _Unwind_Reason_Code (*fn) (_Unwind_Trace_Fn, void *);
+
+      if (handle == NULL)
+	return 0;
+
+      fn = __libc_dlsym (handle, "_Unwind_Backtrace");
+      if (fn == NULL)
+	fn = (void *) -1;
+      unwind_backtrace = fn;
+    }
+  if (unwind_backtrace == (void *) -1)
+    return 0;
+
+  if (size >= 1)
+    unwind_backtrace (backtrace_helper, &arg);
+
+  /* _Unwind_Backtrace on IA-64 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/sysdeps/x86_64/backtrace.c.jj	2003-10-03 15:02:54.000000000 +0200
+++ libc/sysdeps/x86_64/backtrace.c	2003-10-03 15:02:49.000000000 +0200
@@ -0,0 +1 @@
+#include "../ia64/backtrace.c"

	Jakub