[PATCH COMMITTED] Use libgcc unwinder for sparc backtraces, ifavailable.

[David Miller <davem at davemloft dot net>]

This is enough to get all of the test cases to pass, I plan
to enhance this code even more when I get some time by
adding a proper signal handler sniffer so that even without
unwind information we can give a nearly perfect backtrace.

	* sysdeps/sparc/backtrace.c: New file.
	* sysdeps/sparc/sparc32/backtrace.h: New file.
	* sysdeps/sparc/sparc32/sparcv9/backtrace.h: New file.
	* sysdeps/sparc/sparc64/backtrace.h: New file.
	* sysdeps/sparc/sparc64/backtrace.c: Delete.
	* sysdeps/sparc/Makefile (CFLAGS-backtrace.c): Add
	-funwind-tables.
---
 ChangeLog                                 |   10 ++
 sysdeps/sparc/Makefile                    |    4 +
 sysdeps/sparc/backtrace.c                 |  163 +++++++++++++++++++++++++++++
 sysdeps/sparc/sparc32/backtrace.h         |    7 ++
 sysdeps/sparc/sparc32/sparcv9/backtrace.h |    7 ++
 sysdeps/sparc/sparc64/backtrace.c         |   57 ----------
 sysdeps/sparc/sparc64/backtrace.h         |    7 ++
 7 files changed, 198 insertions(+), 57 deletions(-)
 create mode 100644 sysdeps/sparc/backtrace.c
 create mode 100644 sysdeps/sparc/sparc32/backtrace.h
 create mode 100644 sysdeps/sparc/sparc32/sparcv9/backtrace.h
 delete mode 100644 sysdeps/sparc/sparc64/backtrace.c
 create mode 100644 sysdeps/sparc/sparc64/backtrace.h

diff --git a/ChangeLog b/ChangeLog
index 9b53463..7d8eaf7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2013-01-21  David S. Miller  <davem@davemloft.net>
+
+	* sysdeps/sparc/backtrace.c: New file.
+	* sysdeps/sparc/sparc32/backtrace.h: New file.
+	* sysdeps/sparc/sparc32/sparcv9/backtrace.h: New file.
+	* sysdeps/sparc/sparc64/backtrace.h: New file.
+	* sysdeps/sparc/sparc64/backtrace.c: Delete.
+	* sysdeps/sparc/Makefile (CFLAGS-backtrace.c): Add
+	-funwind-tables.
+
 2013-01-21  Andreas Schwab  <schwab@suse.de>
 
 	[BZ #15020]
diff --git a/sysdeps/sparc/Makefile b/sysdeps/sparc/Makefile
index 3f0c096..31aaeae 100644
--- a/sysdeps/sparc/Makefile
+++ b/sysdeps/sparc/Makefile
@@ -3,6 +3,10 @@ long-double-fcts = yes
 
 pie-ccflag = -fPIE
 
+ifeq ($(subdir),debug)
+CFLAGS-backtrace.c += -funwind-tables
+endif
+
 ifeq ($(subdir),gmon)
 sysdep_routines += sparc-mcount
 endif
diff --git a/sysdeps/sparc/backtrace.c b/sysdeps/sparc/backtrace.c
new file mode 100644
index 0000000..89f976b
--- /dev/null
+++ b/sysdeps/sparc/backtrace.c
@@ -0,0 +1,163 @@
+/* Return backtrace of current program state.
+   Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by David S. Miller <davem@davemloft.net>
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#include <execinfo.h>
+#include <stddef.h>
+#include <bp-checks.h>
+#include <sysdep.h>
+#include <sys/trap.h>
+#include <dlfcn.h>
+#include <unwind.h>
+#include <backtrace.h>
+
+struct layout
+{
+  unsigned long locals[8];
+  unsigned long ins[6];
+  unsigned long next;
+  void *__unbounded return_address;
+};
+
+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.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)
+{
+  struct trace_arg *arg = a;
+  _Unwind_Ptr ip;
+
+  /* We are first called with address in the __backtrace function.
+     Skip it.  */
+  if (arg->cnt != -1)
+    {
+      ip = unwind_getip (ctx);
+      arg->array[arg->cnt] = (void *) ip;
+
+      /* 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 };
+  bool use_unwinder;
+  int count;
+
+  if (!size)
+    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)
+    {
+      struct layout *current;
+      unsigned long fp, i7;
+
+      asm volatile ("mov %%fp, %0" : "=r"(fp));
+      asm volatile ("mov %%i7, %0" : "=r"(i7));
+      current = (struct layout *__unbounded) (fp + BACKTRACE_STACK_BIAS);
+      current = BOUNDED_1 (current);
+
+      array[0] = (void *__unbounded) i7;
+
+      if (size == 1)
+	return 1;
+
+      backtrace_flush_register_windows();
+      for (count = 1; count < size; count++)
+	{
+	  array[count] = current->return_address;
+	  if (!current->next)
+	    break;
+	  current = (struct layout *__unbounded) (current->next
+						  + BACKTRACE_STACK_BIAS);
+	  current = BOUNDED_1 (current);
+	}
+    }
+  else
+    {
+      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;
+      count = arg.cnt != -1 ? arg.cnt : 0;
+    }
+  return count;
+}
+weak_alias (__backtrace, backtrace)
+libc_hidden_def (__backtrace)
diff --git a/sysdeps/sparc/sparc32/backtrace.h b/sysdeps/sparc/sparc32/backtrace.h
new file mode 100644
index 0000000..089f8b4
--- /dev/null
+++ b/sysdeps/sparc/sparc32/backtrace.h
@@ -0,0 +1,7 @@
+/* Private macros for guiding the backtrace implementation, sparc32
+   version.  */
+
+#define backtrace_flush_register_windows() \
+	asm volatile ("ta %0" : : "i" (ST_FLUSH_WINDOWS))
+
+#define BACKTRACE_STACK_BIAS	0
diff --git a/sysdeps/sparc/sparc32/sparcv9/backtrace.h b/sysdeps/sparc/sparc32/sparcv9/backtrace.h
new file mode 100644
index 0000000..8d6c756
--- /dev/null
+++ b/sysdeps/sparc/sparc32/sparcv9/backtrace.h
@@ -0,0 +1,7 @@
+/* Private macros for guiding the backtrace implementation, sparc32 v9
+   version.  */
+
+#define backtrace_flush_register_windows() \
+	asm volatile ("flushw")
+
+#define BACKTRACE_STACK_BIAS	0
diff --git a/sysdeps/sparc/sparc64/backtrace.c b/sysdeps/sparc/sparc64/backtrace.c
deleted file mode 100644
index 230ca1f..0000000
--- a/sysdeps/sparc/sparc64/backtrace.c
+++ /dev/null
@@ -1,57 +0,0 @@
-/* Return backtrace of current program state.
-   Copyright (C) 2008-2013 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by David S. Miller <davem@davemloft.net>
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Library General Public License as
-   published by the Free Software Foundation; either version 2 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
-   Library General Public License for more details.
-
-   You should have received a copy of the GNU Library General Public
-   License along with the GNU C Library; see the file COPYING.LIB.  If
-   not, see <http://www.gnu.org/licenses/>.  */
-
-#include <execinfo.h>
-#include <stddef.h>
-#include <bp-checks.h>
-#include <sysdep.h>
-
-struct layout
-{
-  unsigned long locals[8];
-  unsigned long ins[6];
-  unsigned long next;
-  void *__unbounded return_address;
-};
-
-int
-__backtrace (void **array, int size)
-{
-  struct layout *current;
-  unsigned long fp;
-  int count;
-
-  asm volatile ("flushw");
-  asm volatile ("mov %%fp, %0" : "=r"(fp));
-  current = (struct layout *__unbounded) (fp + STACK_BIAS);
-  current = BOUNDED_1 (current);
-
-  for (count = 0; count < size; count++)
-    {
-      array[count] = current->return_address;
-      if (!current->next)
-	break;
-      current = (struct layout *__unbounded) (current->next + STACK_BIAS);
-      current = BOUNDED_1 (current);
-    }
-
-  return count;
-}
-weak_alias (__backtrace, backtrace)
-libc_hidden_def (__backtrace)
diff --git a/sysdeps/sparc/sparc64/backtrace.h b/sysdeps/sparc/sparc64/backtrace.h
new file mode 100644
index 0000000..b9c95c5
--- /dev/null
+++ b/sysdeps/sparc/sparc64/backtrace.h
@@ -0,0 +1,7 @@
+/* Private macros for guiding the backtrace implementation, sparc64
+   version.  */
+
+#define backtrace_flush_register_windows() \
+	asm volatile ("flushw")
+
+#define BACKTRACE_STACK_BIAS	STACK_BIAS
-- 
1.7.10.4