1// Copyright (c) 2013 Google Inc.
2// All rights reserved.
3//
4// Redistribution and use in source and binary forms, with or without
5// modification, are permitted provided that the following conditions are
6// met:
7//
8// * Redistributions of source code must retain the above copyright
9// notice, this list of conditions and the following disclaimer.
10// * Redistributions in binary form must reproduce the above
11// copyright notice, this list of conditions and the following disclaimer
12// in the documentation and/or other materials provided with the
13// distribution.
14// * Neither the name of Google Inc. nor the names of its
15// contributors may be used to endorse or promote products derived from
16// this software without specific prior written permission.
17//
18// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29
30// stackwalker_ppc64.cc: ppc64-specific stackwalker.
31//
32// See stackwalker_ppc64.h for documentation.
33
34
35#include "common/scoped_ptr.h"
36#include "processor/stackwalker_ppc64.h"
37#include "google_breakpad/processor/call_stack.h"
38#include "google_breakpad/processor/memory_region.h"
39#include "google_breakpad/processor/stack_frame_cpu.h"
40#include "processor/logging.h"
41
42#include <stdio.h>
43
44namespace google_breakpad {
45
46
47StackwalkerPPC64::StackwalkerPPC64(const SystemInfo* system_info,
48 const MDRawContextPPC64* context,
49 MemoryRegion* memory,
50 const CodeModules* modules,
51 StackFrameSymbolizer* resolver_helper)
52 : Stackwalker(system_info, memory, modules, resolver_helper),
53 context_(context) {
54}
55
56
57StackFrame* StackwalkerPPC64::GetContextFrame() {
58 if (!context_) {
59 BPLOG(ERROR) << "Can't get context frame without context";
60 return NULL;
61 }
62
63 StackFramePPC64* frame = new StackFramePPC64();
64
65 // The instruction pointer is stored directly in a register, so pull it
66 // straight out of the CPU context structure.
67 frame->context = *context_;
68 frame->context_validity = StackFramePPC64::CONTEXT_VALID_ALL;
69 frame->trust = StackFrame::FRAME_TRUST_CONTEXT;
70 frame->instruction = frame->context.srr0;
71
72 return frame;
73}
74
75
76StackFrame* StackwalkerPPC64::GetCallerFrame(const CallStack* stack,
77 bool stack_scan_allowed) {
78 if (!memory_ || !stack) {
79 BPLOG(ERROR) << "Can't get caller frame without memory or stack";
80 return NULL;
81 }
82
83 // The instruction pointers for previous frames are saved on the stack.
84 // The typical ppc64 calling convention is for the called procedure to store
85 // its return address in the calling procedure's stack frame at 8(%r1),
86 // and to allocate its own stack frame by decrementing %r1 (the stack
87 // pointer) and saving the old value of %r1 at 0(%r1). Because the ppc64 has
88 // no hardware stack, there is no distinction between the stack pointer and
89 // frame pointer, and what is typically thought of as the frame pointer on
90 // an x86 is usually referred to as the stack pointer on a ppc64.
91
92 StackFramePPC64* last_frame = static_cast<StackFramePPC64*>(
93 stack->frames()->back());
94
95 // A caller frame must reside higher in memory than its callee frames.
96 // Anything else is an error, or an indication that we've reached the
97 // end of the stack.
98 uint64_t stack_pointer;
99 if (!memory_->GetMemoryAtAddress(last_frame->context.gpr[1],
100 &stack_pointer) ||
101 stack_pointer <= last_frame->context.gpr[1]) {
102 return NULL;
103 }
104
105 // Mac OS X/Darwin gives 1 as the return address from the bottom-most
106 // frame in a stack (a thread's entry point). I haven't found any
107 // documentation on this, but 0 or 1 would be bogus return addresses,
108 // so check for them here and return false (end of stack) when they're
109 // hit to avoid having a phantom frame.
110 uint64_t instruction;
111 if (!memory_->GetMemoryAtAddress(stack_pointer + 16, &instruction) ||
112 instruction <= 1) {
113 return NULL;
114 }
115
116 scoped_ptr<StackFramePPC64> frame(new StackFramePPC64());
117
118 frame->context = last_frame->context;
119 frame->context.srr0 = instruction;
120 frame->context.gpr[1] = stack_pointer;
121 frame->context_validity = StackFramePPC64::CONTEXT_VALID_SRR0 |
122 StackFramePPC64::CONTEXT_VALID_GPR1;
123 frame->trust = StackFrame::FRAME_TRUST_FP;
124
125 // Should we terminate the stack walk? (end-of-stack or broken invariant)
126 if (TerminateWalk(instruction,
127 stack_pointer,
128 last_frame->context.gpr[1],
129 stack->frames()->size() == 1)) {
130 return NULL;
131 }
132
133 // frame->context.srr0 is the return address, which is one instruction
134 // past the branch that caused us to arrive at the callee. Set
135 // frame_ppc64->instruction to eight less than that. Since all ppc64
136 // instructions are 8 bytes wide, this is the address of the branch
137 // instruction. This allows source line information to match up with the
138 // line that contains a function call. Callers that require the exact
139 // return address value may access the context.srr0 field of StackFramePPC64.
140 frame->instruction = frame->context.srr0 - 8;
141
142 return frame.release();
143}
144
145
146} // namespace google_breakpad
147