PowerPC: fix backtrace to handle signal trampolines

This patch fixes backtrace for PPC32 and PPC64 to correctly handle
signal trampolines. The 'debug/tst-backtrace6.c' also check for
SA_SIGINFO handling, where is triggers another vDSO symbols for PPC32.

ChangeLog

@@ -1,3 +1,20 @@
+2013-07-23  Adhemerval Zanella  <azanella@linux.vnet.ibm.com>
+
+	[BZ #15867]
+	* sysdeps/powerpc/powerpc32/backtrace.c (__backtrace): Handle signal
+	trampoline stack frame information.
+	* sysdeps/powerpc/powerpc64/backtrace.c (__backtrace): Likewise.
+	* sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h
+	(__vdso_sigtramp_rt64): New variable: PPC64 signal trampoline.
+	(__vdso_sigtramp32): New variable: PPC32 signal trampoline.
+	(__vdso_sigtramp_rt32): New variable: PPC32 signal trampoline.
+	* sysdeps/unix/sysv/linux/powerpc/init-first.c
+	(_libc_vdso_platform_setup): Initialize the signal trampolines.
+	* debug/tst-backtrace5.c (fn): Add an option set modify sigaction
+	sa_flags value.
+	* debug/tst-backtrace6.c: New file: check backtrace for signal frames,
+	interrupting a syscall and set with option SA_SIGINFO.
+
 2013-08-20  Joseph Myers  <joseph@codesourcery.com>
 
 	[BZ #15531]

debug/Makefile

@@ -130,16 +130,18 @@ CFLAGS-tst-backtrace2.c += -funwind-tables
 CFLAGS-tst-backtrace3.c += -funwind-tables
 CFLAGS-tst-backtrace4.c += -funwind-tables
 CFLAGS-tst-backtrace5.c += -funwind-tables
+CFLAGS-tst-backtrace6.c += -funwind-tables
 LDFLAGS-tst-backtrace2 = -rdynamic
 LDFLAGS-tst-backtrace3 = -rdynamic
 LDFLAGS-tst-backtrace4 = -rdynamic
 LDFLAGS-tst-backtrace5 = -rdynamic
+LDFLAGS-tst-backtrace6 = -rdynamic
 
 tests = backtrace-tst tst-longjmp_chk tst-chk1 tst-chk2 tst-chk3 \
 	tst-lfschk1 tst-lfschk2 tst-lfschk3 test-strcpy_chk test-stpcpy_chk \
 	tst-chk4 tst-chk5 tst-chk6 tst-lfschk4 tst-lfschk5 tst-lfschk6 \
 	tst-longjmp_chk2 tst-backtrace2 tst-backtrace3 tst-backtrace4 \
-	tst-backtrace5
+	tst-backtrace5 tst-backtrace6
 
 tests-ifunc := $(stpcpy_chk strcpy_chk:%=test-%-ifunc)
 tests += $(tests-ifunc)

debug/tst-backtrace5.c

@@ -28,6 +28,10 @@
 
 #include "tst-backtrace.h"
 
+#ifndef SIGACTION_FLAGS
+# define SIGACTION_FLAGS 0
+#endif
+
 static int do_test (void);
 #define TEST_FUNCTION do_test ()
 #include "../test-skeleton.c"
@@ -91,7 +95,7 @@ handle_signal (int signum)
 }
 
 NO_INLINE int
-fn (int c)
+fn (int c, int flags)
 {
   pid_t parent_pid, child_pid;
   int pipefd[2];
@@ -100,12 +104,13 @@ fn (int c)
 
   if (c > 0)
     {
-      fn (c - 1);
+      fn (c - 1, flags);
       return x;
     }
 
   memset (&act, 0, sizeof (act));
   act.sa_handler = handle_signal;
+  act.sa_flags = flags;
   sigemptyset (&act.sa_mask);
   sigaction (SIGUSR1, &act, NULL);
   parent_pid = getpid ();
@@ -131,6 +136,6 @@ fn (int c)
 NO_INLINE static int
 do_test (void)
 {
-  fn (2);
+  fn (2, SIGACTION_FLAGS);
   return ret;
 }

debug/tst-backtrace6.c

@@ -0,0 +1,21 @@
+/* Test backtrace and backtrace_symbols for signal frames, where a
+   system call was interrupted by a signal.
+   Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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/>.  */
+
+#define SIGACTION_FLAGS SA_SIGINFO
+#include <debug/tst-backtrace5.c>

sysdeps/powerpc/powerpc32/backtrace.c

@@ -18,6 +18,9 @@
 
 #include <execinfo.h>
 #include <stddef.h>
+#include <string.h>
+#include <signal.h>
+#include <bits/libc-vdso.h>
 
 /* This is the stack layout we see with every stack frame.
    Note that every routine is required by the ABI to lay out the stack
@@ -35,6 +38,46 @@ struct layout
   void *return_address;
 };
 
+#define SIGNAL_FRAMESIZE 64
+
+/* Since the signal handler is just like any other function it needs to
+   save/restore its LR and it will save it into callers stack frame.
+   Since a signal handler doesn't have a caller, the kernel creates a
+   dummy frame to make it look like it has a caller.  */
+struct signal_frame_32 {
+  char               dummy[SIGNAL_FRAMESIZE];
+  struct sigcontext  sctx;
+  mcontext_t         mctx;
+  /* We don't care about the rest, since IP value is at 'mctx' field.  */
+};
+
+static inline int
+is_sigtramp_address (unsigned int nip)
+{
+#ifdef SHARED
+  if (nip == (unsigned int)__vdso_sigtramp32)
+    return 1;
+#endif
+  return 0;
+}
+
+struct rt_signal_frame_32 {
+  char               dummy[SIGNAL_FRAMESIZE + 16];
+  siginfo_t          info;
+  struct ucontext    uc;
+  /* We don't care about the rest, since IP value is at 'uc' field.  */
+};
+
+static inline int
+is_sigtramp_address_rt (unsigned int nip)
+{
+#ifdef SHARED
+  if (nip == (unsigned int)__vdso_sigtramp_rt32)
+    return 1;
+#endif
+  return 0;
+}
+
 int
 __backtrace (void **array, int size)
 {
@@ -50,7 +93,28 @@ __backtrace (void **array, int size)
   for (				count = 0;
        current != NULL && 	count < size;
        current = current->next, count++)
-    array[count] = current->return_address;
+    {
+      gregset_t *gregset = NULL;
+
+      array[count] = current->return_address;
+
+      /* Check if the symbol is the signal trampoline and get the interrupted
+       * symbol address from the trampoline saved area.  */
+      if (is_sigtramp_address ((unsigned int)current->return_address))
+	{
+	  struct signal_frame_32 *sigframe =
+	    (struct signal_frame_32*) current;
+          gregset = &sigframe->mctx.gregs;
+        }
+      else if (is_sigtramp_address_rt ((unsigned int)current->return_address))
+	{
+	  struct rt_signal_frame_32 *sigframe =
+            (struct rt_signal_frame_32*) current;
+          gregset = &sigframe->uc.uc_mcontext.uc_regs->gregs;
+        }
+      if (gregset)
+	array[++count] = (void*)((*gregset)[PT_NIP]);
+    }
 
   /* It's possible the second-last stack frame can't return
      (that is, it's __libc_start_main), in which case

sysdeps/powerpc/powerpc64/backtrace.c

@@ -18,6 +18,9 @@
 
 #include <execinfo.h>
 #include <stddef.h>
+#include <string.h>
+#include <signal.h>
+#include <bits/libc-vdso.h>
 
 /* This is the stack layout we see with every stack frame.
    Note that every routine is required by the ABI to lay out the stack
@@ -38,6 +41,27 @@ struct layout
   void *return_address;
 };
 
+/* Since the signal handler is just like any other function it needs to
+   save/restore its LR and it will save it into callers stack frame.
+   Since a signal handler doesn't have a caller, the kernel creates a
+   dummy frame to make it look like it has a caller.  */
+struct signal_frame_64 {
+#define SIGNAL_FRAMESIZE 128
+  char            dummy[SIGNAL_FRAMESIZE];
+  struct ucontext uc;
+  /* We don't care about the rest, since the IP value is at 'uc' field.  */
+};
+
+static inline int
+is_sigtramp_address (unsigned long nip)
+{
+#ifdef SHARED
+  if (nip == (unsigned long)__vdso_sigtramp_rt64)
+    return 1;
+#endif
+  return 0;
+}
+
 int
 __backtrace (void **array, int size)
 {
@@ -53,7 +77,17 @@ __backtrace (void **array, int size)
   for (				count = 0;
        current != NULL && 	count < size;
        current = current->next, count++)
-    array[count] = current->return_address;
+    {
+      array[count] = current->return_address;
+
+      /* Check if the symbol is the signal trampoline and get the interrupted
+       * symbol address from the trampoline saved area.  */
+      if (is_sigtramp_address ((unsigned long)current->return_address))
+        {
+	  struct signal_frame_64 *sigframe = (struct signal_frame_64*) current;
+          array[++count] = (void*)sigframe->uc.uc_mcontext.gp_regs[PT_NIP];
+	}
+    }
 
   /* It's possible the second-last stack frame can't return
      (that is, it's __libc_start_main), in which case

sysdeps/unix/sysv/linux/powerpc/bits/libc-vdso.h

@@ -34,6 +34,13 @@ extern void *__vdso_getcpu;
 
 extern void *__vdso_time;
 
+#if defined(__PPC64__) || defined(__powerpc64__)
+extern void *__vdso_sigtramp_rt64;
+#else
+extern void *__vdso_sigtramp32;
+extern void *__vdso_sigtramp_rt32;
+#endif
+
 /* This macro is needed for PPC64 to return a skeleton OPD entry of a vDSO
    symbol.  This works because _dl_vdso_vsym always return the function
    address, and no vDSO symbols use the TOC or chain pointers from the OPD

sysdeps/unix/sysv/linux/powerpc/init-first.c

@@ -29,6 +29,12 @@ void *__vdso_clock_getres;
 void *__vdso_get_tbfreq;
 void *__vdso_getcpu;
 void *__vdso_time;
+#if defined(__PPC64__) || defined(__powerpc64__)
+void *__vdso_sigtramp_rt64;
+#else
+void *__vdso_sigtramp32;
+void *__vdso_sigtramp_rt32;
+#endif
 
 static inline void
 _libc_vdso_platform_setup (void)
@@ -46,6 +52,16 @@ _libc_vdso_platform_setup (void)
   __vdso_getcpu = _dl_vdso_vsym ("__kernel_getcpu", &linux2615);
 
   __vdso_time = _dl_vdso_vsym ("__kernel_time", &linux2615);
+
+  /* PPC64 uses only one signal trampoline symbol, while PPC32 will use
+     two depending if SA_SIGINFO is used (__kernel_sigtramp_rt32) or not
+     (__kernel_sigtramp32).  */
+#if defined(__PPC64__) || defined(__powerpc64__)
+  __vdso_sigtramp_rt64 = _dl_vdso_vsym ("__kernel_sigtramp_rt64", &linux2615);
+#else
+  __vdso_sigtramp32 = _dl_vdso_vsym ("__kernel_sigtramp32", &linux2615);
+  __vdso_sigtramp_rt32 = _dl_vdso_vsym ("__kernel_sigtramp_rt32", &linux2615);
+#endif
 }
 
 # define VDSO_SETUP _libc_vdso_platform_setup