1 // Copyright 2010 Google LLC
2 //
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4 // modification, are permitted provided that the following conditions are
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6 //
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27 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28
29 // stackwalker_ppc.cc: ppc-specific stackwalker.
30 //
31 // See stackwalker_ppc.h for documentation.
32 //
33 // Author: Mark Mentovai
34
35
36 #ifdef HAVE_CONFIG_H
37 #include <config.h> // Must come first
38 #endif
39
40 #include "common/scoped_ptr.h"
41 #include "processor/stackwalker_ppc.h"
42 #include "google_breakpad/processor/call_stack.h"
43 #include "google_breakpad/processor/memory_region.h"
44 #include "google_breakpad/processor/stack_frame_cpu.h"
45 #include "processor/logging.h"
46
47 namespace google_breakpad {
48
49
StackwalkerPPC(const SystemInfo * system_info,const MDRawContextPPC * context,MemoryRegion * memory,const CodeModules * modules,StackFrameSymbolizer * resolver_helper)50 StackwalkerPPC::StackwalkerPPC(const SystemInfo* system_info,
51 const MDRawContextPPC* context,
52 MemoryRegion* memory,
53 const CodeModules* modules,
54 StackFrameSymbolizer* resolver_helper)
55 : Stackwalker(system_info, memory, modules, resolver_helper),
56 context_(context) {
57 if (memory_ && memory_->GetBase() + memory_->GetSize() - 1 > 0xffffffff) {
58 // This implementation only covers 32-bit ppc CPUs. The limits of the
59 // supplied stack are invalid. Mark memory_ = NULL, which will cause
60 // stackwalking to fail.
61 BPLOG(ERROR) << "Memory out of range for stackwalking: " <<
62 HexString(memory_->GetBase()) << "+" <<
63 HexString(memory_->GetSize());
64 memory_ = NULL;
65 }
66 }
67
68
GetContextFrame()69 StackFrame* StackwalkerPPC::GetContextFrame() {
70 if (!context_) {
71 BPLOG(ERROR) << "Can't get context frame without context";
72 return NULL;
73 }
74
75 StackFramePPC* frame = new StackFramePPC();
76
77 // The instruction pointer is stored directly in a register, so pull it
78 // straight out of the CPU context structure.
79 frame->context = *context_;
80 frame->context_validity = StackFramePPC::CONTEXT_VALID_ALL;
81 frame->trust = StackFrame::FRAME_TRUST_CONTEXT;
82 frame->instruction = frame->context.srr0;
83
84 return frame;
85 }
86
87
GetCallerFrame(const CallStack * stack,bool stack_scan_allowed)88 StackFrame* StackwalkerPPC::GetCallerFrame(const CallStack* stack,
89 bool stack_scan_allowed) {
90 if (!memory_ || !stack) {
91 BPLOG(ERROR) << "Can't get caller frame without memory or stack";
92 return NULL;
93 }
94
95 // The instruction pointers for previous frames are saved on the stack.
96 // The typical ppc calling convention is for the called procedure to store
97 // its return address in the calling procedure's stack frame at 8(%r1),
98 // and to allocate its own stack frame by decrementing %r1 (the stack
99 // pointer) and saving the old value of %r1 at 0(%r1). Because the ppc has
100 // no hardware stack, there is no distinction between the stack pointer and
101 // frame pointer, and what is typically thought of as the frame pointer on
102 // an x86 is usually referred to as the stack pointer on a ppc.
103
104 StackFramePPC* last_frame = static_cast<StackFramePPC*>(
105 stack->frames()->back());
106
107 // A caller frame must reside higher in memory than its callee frames.
108 // Anything else is an error, or an indication that we've reached the
109 // end of the stack.
110 uint32_t stack_pointer;
111 if (!memory_->GetMemoryAtAddress(last_frame->context.gpr[1],
112 &stack_pointer) ||
113 stack_pointer <= last_frame->context.gpr[1]) {
114 return NULL;
115 }
116
117 // Mac OS X/Darwin gives 1 as the return address from the bottom-most
118 // frame in a stack (a thread's entry point). I haven't found any
119 // documentation on this, but 0 or 1 would be bogus return addresses,
120 // so check for them here and return false (end of stack) when they're
121 // hit to avoid having a phantom frame.
122 uint32_t instruction;
123 if (!memory_->GetMemoryAtAddress(stack_pointer + 8, &instruction) ||
124 instruction <= 1) {
125 return NULL;
126 }
127
128 scoped_ptr<StackFramePPC> frame(new StackFramePPC());
129
130 frame->context = last_frame->context;
131 frame->context.srr0 = instruction;
132 frame->context.gpr[1] = stack_pointer;
133 frame->context_validity = StackFramePPC::CONTEXT_VALID_SRR0 |
134 StackFramePPC::CONTEXT_VALID_GPR1;
135 frame->trust = StackFrame::FRAME_TRUST_FP;
136
137 // Should we terminate the stack walk? (end-of-stack or broken invariant)
138 if (TerminateWalk(instruction, stack_pointer, last_frame->context.gpr[1],
139 /*first_unwind=*/last_frame->trust ==
140 StackFrame::FRAME_TRUST_CONTEXT)) {
141 return NULL;
142 }
143
144 // frame->context.srr0 is the return address, which is one instruction
145 // past the branch that caused us to arrive at the callee. Set
146 // frame_ppc->instruction to four less than that. Since all ppc
147 // instructions are 4 bytes wide, this is the address of the branch
148 // instruction. This allows source line information to match up with the
149 // line that contains a function call. Callers that require the exact
150 // return address value may access the context.srr0 field of StackFramePPC.
151 frame->instruction = frame->context.srr0 - 4;
152
153 return frame.release();
154 }
155
156
157 } // namespace google_breakpad
158