1  // Copyright 2013 Google LLC
  2  //
  3  // Redistribution and use in source and binary forms, with or without
  4  // modification, are permitted provided that the following conditions are
  5  // met:
  6  //
  7  //     * Redistributions of source code must retain the above copyright
  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.
 13  //     * Neither the name of Google LLC nor the names of its
 14  // contributors may be used to endorse or promote products derived from
 15  // this software without specific prior written permission.
 16  //
 17  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 18  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 19  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 20  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 21  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 22  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 23  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 24  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 25  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 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_ppc64.cc: ppc64-specific stackwalker.
 30  //
 31  // See stackwalker_ppc64.h for documentation.
 32  
 33  
 34  #ifdef HAVE_CONFIG_H
 35  #include <config.h>  // Must come first
 36  #endif
 37  
 38  #include "common/scoped_ptr.h"
 39  #include "processor/stackwalker_ppc64.h"
 40  #include "google_breakpad/processor/call_stack.h"
 41  #include "google_breakpad/processor/memory_region.h"
 42  #include "google_breakpad/processor/stack_frame_cpu.h"
 43  #include "processor/logging.h"
 44  
 45  #include <stdio.h>
 46  
 47  namespace google_breakpad {
 48  
 49  
 50  StackwalkerPPC64::StackwalkerPPC64(const SystemInfo* system_info,
 51                                     const MDRawContextPPC64* context,
 52                                     MemoryRegion* memory,
 53                                     const CodeModules* modules,
 54                                     StackFrameSymbolizer* resolver_helper)
 55      : Stackwalker(system_info, memory, modules, resolver_helper),
 56        context_(context) {
 57  }
 58  
 59  
 60  StackFrame* StackwalkerPPC64::GetContextFrame() {
 61    if (!context_) {
 62      BPLOG(ERROR) << "Can't get context frame without context";
 63      return NULL;
 64    }
 65  
 66    StackFramePPC64* frame = new StackFramePPC64();
 67  
 68    // The instruction pointer is stored directly in a register, so pull it
 69    // straight out of the CPU context structure.
 70    frame->context = *context_;
 71    frame->context_validity = StackFramePPC64::CONTEXT_VALID_ALL;
 72    frame->trust = StackFrame::FRAME_TRUST_CONTEXT;
 73    frame->instruction = frame->context.srr0;
 74  
 75    return frame;
 76  }
 77  
 78  
 79  StackFrame* StackwalkerPPC64::GetCallerFrame(const CallStack* stack,
 80                                               bool stack_scan_allowed) {
 81    if (!memory_ || !stack) {
 82      BPLOG(ERROR) << "Can't get caller frame without memory or stack";
 83      return NULL;
 84    }
 85  
 86    // The instruction pointers for previous frames are saved on the stack.
 87    // The typical ppc64 calling convention is for the called procedure to store
 88    // its return address in the calling procedure's stack frame at 8(%r1),
 89    // and to allocate its own stack frame by decrementing %r1 (the stack
 90    // pointer) and saving the old value of %r1 at 0(%r1).  Because the ppc64 has
 91    // no hardware stack, there is no distinction between the stack pointer and
 92    // frame pointer, and what is typically thought of as the frame pointer on
 93    // an x86 is usually referred to as the stack pointer on a ppc64.
 94  
 95    StackFramePPC64* last_frame = static_cast<StackFramePPC64*>(
 96        stack->frames()->back());
 97  
 98    // A caller frame must reside higher in memory than its callee frames.
 99    // Anything else is an error, or an indication that we've reached the
100    // end of the stack.
101    uint64_t stack_pointer;
102    if (!memory_->GetMemoryAtAddress(last_frame->context.gpr[1],
103                                     &stack_pointer) ||
104        stack_pointer <= last_frame->context.gpr[1]) {
105      return NULL;
106    }
107  
108    // Mac OS X/Darwin gives 1 as the return address from the bottom-most
109    // frame in a stack (a thread's entry point).  I haven't found any
110    // documentation on this, but 0 or 1 would be bogus return addresses,
111    // so check for them here and return false (end of stack) when they're
112    // hit to avoid having a phantom frame.
113    uint64_t instruction;
114    if (!memory_->GetMemoryAtAddress(stack_pointer + 16, &instruction) ||
115        instruction <= 1) {
116      return NULL;
117    }
118  
119    scoped_ptr<StackFramePPC64> frame(new StackFramePPC64());
120  
121    frame->context = last_frame->context;
122    frame->context.srr0 = instruction;
123    frame->context.gpr[1] = stack_pointer;
124    frame->context_validity = StackFramePPC64::CONTEXT_VALID_SRR0 |
125                              StackFramePPC64::CONTEXT_VALID_GPR1;
126    frame->trust = StackFrame::FRAME_TRUST_FP;
127  
128    // Should we terminate the stack walk? (end-of-stack or broken invariant)
129    if (TerminateWalk(instruction, stack_pointer, last_frame->context.gpr[1],
130                      /*is_context_frame=*/last_frame->trust ==
131                          StackFrame::FRAME_TRUST_CONTEXT)) {
132      return NULL;
133    }
134  
135    // frame->context.srr0 is the return address, which is one instruction
136    // past the branch that caused us to arrive at the callee.  Set
137    // frame_ppc64->instruction to eight less than that.  Since all ppc64
138    // instructions are 8 bytes wide, this is the address of the branch
139    // instruction.  This allows source line information to match up with the
140    // line that contains a function call.  Callers that require the exact
141    // return address value may access the context.srr0 field of StackFramePPC64.
142    frame->instruction = frame->context.srr0 - 8;
143  
144    return frame.release();
145  }
146  
147  
148  }  // namespace google_breakpad