1// Copyright (c) 2010 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_ppc.cc: ppc-specific stackwalker.
31//
32// See stackwalker_ppc.h for documentation.
33//
34// Author: Mark Mentovai
35
36
37#include "common/scoped_ptr.h"
38#include "processor/stackwalker_ppc.h"
39#include "google_breakpad/processor/call_stack.h"
40#include "google_breakpad/processor/memory_region.h"
41#include "google_breakpad/processor/stack_frame_cpu.h"
42#include "processor/logging.h"
43
44namespace google_breakpad {
45
46
47StackwalkerPPC::StackwalkerPPC(const SystemInfo* system_info,
48 const MDRawContextPPC* context,
49 MemoryRegion* memory,
50 const CodeModules* modules,
51 StackFrameSymbolizer* resolver_helper)
52 : Stackwalker(system_info, memory, modules, resolver_helper),
53 context_(context) {
54 if (memory_ && memory_->GetBase() + memory_->GetSize() - 1 > 0xffffffff) {
55 // This implementation only covers 32-bit ppc CPUs. The limits of the
56 // supplied stack are invalid. Mark memory_ = NULL, which will cause
57 // stackwalking to fail.
58 BPLOG(ERROR) << "Memory out of range for stackwalking: " <<
59 HexString(memory_->GetBase()) << "+" <<
60 HexString(memory_->GetSize());
61 memory_ = NULL;
62 }
63}
64
65
66StackFrame* StackwalkerPPC::GetContextFrame() {
67 if (!context_) {
68 BPLOG(ERROR) << "Can't get context frame without context";
69 return NULL;
70 }
71
72 StackFramePPC* frame = new StackFramePPC();
73
74 // The instruction pointer is stored directly in a register, so pull it
75 // straight out of the CPU context structure.
76 frame->context = *context_;
77 frame->context_validity = StackFramePPC::CONTEXT_VALID_ALL;
78 frame->trust = StackFrame::FRAME_TRUST_CONTEXT;
79 frame->instruction = frame->context.srr0;
80
81 return frame;
82}
83
84
85StackFrame* StackwalkerPPC::GetCallerFrame(const CallStack* stack,
86 bool stack_scan_allowed) {
87 if (!memory_ || !stack) {
88 BPLOG(ERROR) << "Can't get caller frame without memory or stack";
89 return NULL;
90 }
91
92 // The instruction pointers for previous frames are saved on the stack.
93 // The typical ppc calling convention is for the called procedure to store
94 // its return address in the calling procedure's stack frame at 8(%r1),
95 // and to allocate its own stack frame by decrementing %r1 (the stack
96 // pointer) and saving the old value of %r1 at 0(%r1). Because the ppc has
97 // no hardware stack, there is no distinction between the stack pointer and
98 // frame pointer, and what is typically thought of as the frame pointer on
99 // an x86 is usually referred to as the stack pointer on a ppc.
100
101 StackFramePPC* last_frame = static_cast<StackFramePPC*>(
102 stack->frames()->back());
103
104 // A caller frame must reside higher in memory than its callee frames.
105 // Anything else is an error, or an indication that we've reached the
106 // end of the stack.
107 uint32_t stack_pointer;
108 if (!memory_->GetMemoryAtAddress(last_frame->context.gpr[1],
109 &stack_pointer) ||
110 stack_pointer <= last_frame->context.gpr[1]) {
111 return NULL;
112 }
113
114 // Mac OS X/Darwin gives 1 as the return address from the bottom-most
115 // frame in a stack (a thread's entry point). I haven't found any
116 // documentation on this, but 0 or 1 would be bogus return addresses,
117 // so check for them here and return false (end of stack) when they're
118 // hit to avoid having a phantom frame.
119 uint32_t instruction;
120 if (!memory_->GetMemoryAtAddress(stack_pointer + 8, &instruction) ||
121 instruction <= 1) {
122 return NULL;
123 }
124
125 scoped_ptr<StackFramePPC> frame(new StackFramePPC());
126
127 frame->context = last_frame->context;
128 frame->context.srr0 = instruction;
129 frame->context.gpr[1] = stack_pointer;
130 frame->context_validity = StackFramePPC::CONTEXT_VALID_SRR0 |
131 StackFramePPC::CONTEXT_VALID_GPR1;
132 frame->trust = StackFrame::FRAME_TRUST_FP;
133
134 // Should we terminate the stack walk? (end-of-stack or broken invariant)
135 if (TerminateWalk(instruction,
136 stack_pointer,
137 last_frame->context.gpr[1],
138 stack->frames()->size() == 1)) {
139 return NULL;
140 }
141
142 // frame->context.srr0 is the return address, which is one instruction
143 // past the branch that caused us to arrive at the callee. Set
144 // frame_ppc->instruction to four less than that. Since all ppc
145 // instructions are 4 bytes wide, this is the address of the branch
146 // instruction. This allows source line information to match up with the
147 // line that contains a function call. Callers that require the exact
148 // return address value may access the context.srr0 field of StackFramePPC.
149 frame->instruction = frame->context.srr0 - 4;
150
151 return frame.release();
152}
153
154
155} // namespace google_breakpad
156