PowerPC: stacktrace function refactor and fixes

This patch fixes the stacktrace creating when the function is
interrupted by a signal. For Linux, the vDSO signal trampoline symbol is
compared against LR from stack backchain and handled different in that
case (since the signal trampoline layout a different stack frame).

Because of this extensive change the PowerPC stacktrace code has now
been refactored to split in Linux and Darwin specific codes.

src/stacktrace.cc

@@ -109,7 +109,11 @@ struct GetStackImplementation {
 #endif // i386 || x86_64
 
 #if defined(__ppc__) || defined(__PPC__)
-#define STACKTRACE_INL_HEADER "stacktrace_powerpc-inl.h"
+#if defined(__linux__)
+#define STACKTRACE_INL_HEADER "stacktrace_powerpc-linux-inl.h"
+#else
+#define STACKTRACE_INL_HEADER "stacktrace_powerpc-darwin-inl.h"
+#endif
 #define GST_SUFFIX ppc
 #include "stacktrace_impl_setup-inl.h"
 #undef GST_SUFFIX

src/stacktrace_powerpc-darwin-inl.h

@@ -0,0 +1,158 @@
+// Copyright (c) 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// ---
+// Produce stack trace.  ABI documentation reference can be found at:
+// * PowerPC32 ABI: https://www.power.org/documentation/
+// power-architecture-32-bit-abi-supplement-1-0-embeddedlinuxunified/
+// * PowerPC64 ABI:
+// http://www.linux-foundation.org/spec/ELF/ppc64/PPC-elf64abi-1.9.html#STACK
+
+#ifndef BASE_STACKTRACE_POWERPC_INL_H_
+#define BASE_STACKTRACE_POWERPC_INL_H_
+// Note: this file is included into stacktrace.cc more than once.
+// Anything that should only be defined once should be here:
+
+#include <stdint.h>   // for uintptr_t
+#include <stdlib.h>   // for NULL
+#include <gperftools/stacktrace.h>
+
+// Given a pointer to a stack frame, locate and return the calling
+// stackframe, or return NULL if no stackframe can be found. Perform sanity
+// checks (the strictness of which is controlled by the boolean parameter
+// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
+template<bool STRICT_UNWINDING>
+static void **NextStackFrame(void **old_sp) {
+  void **new_sp = (void **) *old_sp;
+
+  // Check that the transition from frame pointer old_sp to frame
+  // pointer new_sp isn't clearly bogus
+  if (STRICT_UNWINDING) {
+    // With the stack growing downwards, older stack frame must be
+    // at a greater address that the current one.
+    if (new_sp <= old_sp) return NULL;
+    // Assume stack frames larger than 100,000 bytes are bogus.
+    if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000) return NULL;
+  } else {
+    // In the non-strict mode, allow discontiguous stack frames.
+    // (alternate-signal-stacks for example).
+    if (new_sp == old_sp) return NULL;
+    // And allow frames upto about 1MB.
+    if ((new_sp > old_sp)
+        && ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000)) return NULL;
+  }
+  if ((uintptr_t)new_sp & (sizeof(void *) - 1)) return NULL;
+  return new_sp;
+}
+
+// This ensures that GetStackTrace stes up the Link Register properly.
+void StacktracePowerPCDummyFunction() __attribute__((noinline));
+void StacktracePowerPCDummyFunction() { __asm__ volatile(""); }
+#endif  // BASE_STACKTRACE_POWERPC_INL_H_
+
+// Note: this part of the file is included several times.
+// Do not put globals below.
+
+// The following 4 functions are generated from the code below:
+//   GetStack{Trace,Frames}()
+//   GetStack{Trace,Frames}WithContext()
+//
+// These functions take the following args:
+//   void** result: the stack-trace, as an array
+//   int* sizes: the size of each stack frame, as an array
+//               (GetStackFrames* only)
+//   int max_depth: the size of the result (and sizes) array(s)
+//   int skip_count: how many stack pointers to skip before storing in result
+//   void* ucp: a ucontext_t* (GetStack{Trace,Frames}WithContext only)
+int GET_STACK_TRACE_OR_FRAMES {
+  void **sp;
+  // Apple OS X uses an old version of gnu as -- both Darwin 7.9.0 (Panther)
+  // and Darwin 8.8.1 (Tiger) use as 1.38.  This means we have to use a
+  // different asm syntax.  I don't know quite the best way to discriminate
+  // systems using the old as from the new one; I've gone with __APPLE__.
+  // TODO(csilvers): use autoconf instead, to look for 'as --version' == 1 or 2
+  __asm__ volatile ("mr %0,r1" : "=r" (sp));
+
+  // On PowerPC, the "Link Register" or "Link Record" (LR), is a stack
+  // entry that holds the return address of the subroutine call (what
+  // instruction we run after our function finishes).  This is the
+  // same as the stack-pointer of our parent routine, which is what we
+  // want here.  While the compiler will always(?) set up LR for
+  // subroutine calls, it may not for leaf functions (such as this one).
+  // This routine forces the compiler (at least gcc) to push it anyway.
+  StacktracePowerPCDummyFunction();
+
+#if IS_STACK_FRAMES
+  // Note we do *not* increment skip_count here for the SYSV ABI.  If
+  // we did, the list of stack frames wouldn't properly match up with
+  // the list of return addresses.  Note this means the top pc entry
+  // is probably bogus for linux/ppc (and other SYSV-ABI systems).
+#else
+  // The LR save area is used by the callee, so the top entry is bogus.
+  skip_count++;
+#endif
+
+  int n = 0;
+  while (sp && n < max_depth) {
+    // The GetStackFrames routine is called when we are in some
+    // informational context (the failure signal handler for example).
+    // Use the non-strict unwinding rules to produce a stack trace
+    // that is as complete as possible (even if it contains a few
+    // bogus entries in some rare cases).
+    void **next_sp = NextStackFrame<!IS_STACK_FRAMES>(sp);
+
+    if (skip_count > 0) {
+      skip_count--;
+    } else {
+      // PowerPC has 3 main ABIs, which say where in the stack the
+      // Link Register is.  For DARWIN and AIX (used by apple and
+      // linux ppc64), it's in sp[2].  For SYSV (used by linux ppc),
+      // it's in sp[1].
+#if defined(__PPC64__)
+      // This check is in case the compiler doesn't define _CALL_AIX/etc.
+      result[n] = *(sp+2);
+#elif defined(__linux)
+      // This check is in case the compiler doesn't define _CALL_SYSV.
+      result[n] = *(sp+1);
+#endif
+
+#if IS_STACK_FRAMES
+      if (next_sp > sp) {
+        sizes[n] = (uintptr_t)next_sp - (uintptr_t)sp;
+      } else {
+        // A frame-size of 0 is used to indicate unknown frame size.
+        sizes[n] = 0;
+      }
+#endif
+      n++;
+    }
+    sp = next_sp;
+  }
+  return n;
+}

src/stacktrace_powerpc-linux-inl.h

@@ -1,11 +1,11 @@
 // -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
 // Copyright (c) 2007, Google Inc.
 // All rights reserved.
-// 
+//
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
-// 
+//
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ -15,7 +15,7 @@
 //     * Neither the name of Google Inc. nor the names of its
 // contributors may be used to endorse or promote products derived from
 // this software without specific prior written permission.
-// 
+//
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
@@ -31,11 +31,11 @@
 // ---
 // Author: Craig Silverstein
 //
-// Produce stack trace.  I'm guessing (hoping!) the code is much like
+// Produce stack trace.  ABI documentation reference can be found at:
-// for x86.  For apple machines, at least, it seems to be; see
+// * PowerPC32 ABI: https://www.power.org/documentation/
-//    http://developer.apple.com/documentation/mac/runtimehtml/RTArch-59.html
+// power-architecture-32-bit-abi-supplement-1-0-embeddedlinuxunified/
-//    http://www.linux-foundation.org/spec/ELF/ppc64/PPC-elf64abi-1.9.html#STACK
+// * PowerPC64 ABI:
-// Linux has similar code: http://patchwork.ozlabs.org/linuxppc/patch?id=8882
+// http://www.linux-foundation.org/spec/ELF/ppc64/PPC-elf64abi-1.9.html#STACK
 
 #ifndef BASE_STACKTRACE_POWERPC_INL_H_
 #define BASE_STACKTRACE_POWERPC_INL_H_
@@ -45,15 +45,36 @@
 #include <stdint.h>   // for uintptr_t
 #include <stdlib.h>   // for NULL
 #include <gperftools/stacktrace.h>
+#include <base/vdso_support.h>
 
+#if defined(HAVE_SYS_UCONTEXT_H)
+#include <sys/ucontext.h>
+#elif defined(HAVE_UCONTEXT_H)
+#include <ucontext.h>  // for ucontext_t
+#endif
+typedef ucontext ucontext_t;
+
+// PowerPC64 Little Endian follows BE wrt. backchain, condition register,
+// and LR save area, so no need to adjust the reading struct.
 struct layout_ppc {
   struct layout_ppc *next;
-#if defined(__APPLE__) || (defined(__linux) && defined(__PPC64__))
+#ifdef __PPC64__
   long condition_register;
 #endif
   void *return_addr;
 };
 
+// Signal callbacks are handled by the vDSO symbol:
+//
+// * PowerPC64 Linux (arch/powerpc/kernel/vdso64/sigtramp.S):
+//   __kernel_sigtramp_rt64
+// * PowerPC32 Linux (arch/powerpc/kernel/vdso32/sigtramp.S):
+//   __kernel_sigtramp32
+//   __kernel_sigtramp_rt32
+//
+// So a backtrace may need to specially handling if the symbol readed is
+// the signal trampoline.
+
 // Given a pointer to a stack frame, locate and return the calling
 // stackframe, or return NULL if no stackframe can be found. Perform sanity
 // checks (the strictness of which is controlled by the boolean parameter
@@ -102,19 +123,6 @@ void StacktracePowerPCDummyFunction() { __asm__ volatile(""); }
 # define LOAD "lwz"
 #endif
 
-#if defined(__linux__) && defined(__PPC__)
-# define TOP_STACK "%0,0(1)"
-#elif defined(__MACH__) && defined(__APPLE__)
-// Apple OS X uses an old version of gnu as -- both Darwin 7.9.0 (Panther)
-// and Darwin 8.8.1 (Tiger) use as 1.38.  This means we have to use a
-// different asm syntax.  I don't know quite the best way to discriminate
-// systems using the old as from the new one; I've gone with __APPLE__.
-// TODO(csilvers): use autoconf instead, to look for 'as --version' == 1 or 2
-# define TOP_STACK "%0,0(r1)"
-#endif
-
-
-
 // The following 4 functions are generated from the code below:
 //   GetStack{Trace,Frames}()
 //   GetStack{Trace,Frames}WithContext()
@@ -130,17 +138,35 @@ static int GET_STACK_TRACE_OR_FRAMES {
   layout_ppc *current;
   int n;
 
-  // Force GCC to spill LR.
-  asm volatile ("" : "=l"(current));
-
   // Get the address on top-of-stack
-  asm volatile (LOAD " " TOP_STACK : "=r"(current));
+  current = reinterpret_cast<layout_ppc*> (__builtin_frame_address (0));
+  // And ignore the current symbol
+  current = current->next;
 
   StacktracePowerPCDummyFunction();
 
   n = 0;
   skip_count++; // skip parent's frame due to indirection in
                 // stacktrace.cc
+
+  base::VDSOSupport vdso;
+  base::ElfMemImage::SymbolInfo rt_sigreturn_symbol_info;
+#ifdef __PPC64__
+  const void *sigtramp64_vdso = 0;
+  if (vdso.LookupSymbol("__kernel_sigtramp_rt64", "LINUX_2.6.15", STT_NOTYPE,
+                        &rt_sigreturn_symbol_info))
+    sigtramp64_vdso = rt_sigreturn_symbol_info.address;
+#else
+  const void *sigtramp32_vdso = 0;
+  if (vdso.LookupSymbol("__kernel_sigtramp32", "LINUX_2.6.15", STT_NOTYPE,
+                        &rt_sigreturn_symbol_info))
+    sigtramp32_vdso = rt_sigreturn_symbol_info.address;
+  const void *sigtramp32_rt_vdso = 0;
+  if (vdso.LookupSymbol("__kernel_sigtramp_rt32", "LINUX_2.6.15", STT_NOTYPE,
+                        &rt_sigreturn_symbol_info))
+    sigtramp32_rt_vdso = rt_sigreturn_symbol_info.address;
+#endif
+
   while (current && n < max_depth) {
 
     // The GetStackFrames routine is called when we are in some
@@ -153,6 +179,35 @@ static int GET_STACK_TRACE_OR_FRAMES {
       skip_count--;
     } else {
       result[n] = current->return_addr;
+#ifdef __PPC64__
+      if (sigtramp64_vdso && (sigtramp64_vdso == current->return_addr)) {
+        struct signal_frame_64 {
+          char dummy[128];
+          ucontext_t uc;
+        // We don't care about the rest, since the IP value is at 'uc' field.
+        } *sigframe = reinterpret_cast<signal_frame_64*>(current);
+        result[n] = (void*) sigframe->uc.uc_mcontext.gp_regs[PT_NIP];
+      }
+#else
+      if (sigtramp32_vdso && (sigtramp32_vdso == current->return_addr)) {
+        struct signal_frame_32 {
+          char dummy[64];
+          struct sigcontext sctx;
+          mcontext_t mctx;
+          // We don't care about the rest, since IP value is at 'mctx' field.
+        } *sigframe = reinterpret_cast<signal_frame_32*>(current);
+        result[n] = (void*) sigframe->mctx.gregs[PT_NIP];
+      } else if (sigtramp32_rt_vdso && (sigtramp32_rt_vdso == current->return_addr)) {
+        struct rt_signal_frame_32 {
+          char dummy[64 + 16];
+          siginfo_t info;
+          struct ucontext uc;
+          // We don't care about the rest, since IP value is at 'uc' field.A
+        } *sigframe = reinterpret_cast<rt_signal_frame_32*>(current);
+        result[n] = (void*) sigframe->uc.uc_mcontext.uc_regs->gregs[PT_NIP];
+      }
+#endif
+
 #if IS_STACK_FRAMES
       if (next > current) {
         sizes[n] = (uintptr_t)next - (uintptr_t)current;