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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  8  // notice, this list of conditions and the following disclaimer.
  9  //     * Redistributions in binary form must reproduce the above
 10  // copyright notice, this list of conditions and the following disclaimer
 11  // in the documentation and/or other materials provided with the
 12  // distribution.
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 14  // contributors may be used to endorse or promote products derived from
 15  // this software without specific prior written permission.
 16  //
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 20  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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 22  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 23  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 26  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 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  
 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  
 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  
 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