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breakpad/src/processor/stackwalker_mips.cc
Leonard Mosescu 01431c2f61 Handle very large stack traces 
The main motivation for this change is to handle very large stack
traces, normally the result of infinite recursion. This part is
actually fairly simple, relaxing a few self-imposed limits on how
many frames we can unwind and the max size for stack memory.

Relaxing these limits requires stricter and more consistent checks for
stack unwinding. There are a number of unwinding invariants that apply
to all the platforms:

1. stack pointer (and frame pointer) must be within the stack memory
   (frame pointer, if preset, must point to the right frame too)
2. unwinding must monotonically increase SP
   (except for the first frame unwind, this must be a strict increase)
3. Instruction pointer (return address) must point to a valid location
4. stack pointer (and frame pointer) must be appropriately aligned

This change is focused on 2), which is enough to guarantee that the
unwinding doesn't get stuck in an infinite loop.

1) is implicitly validated part of accessing the stack memory
   (explicit checks might be nice though).
4) is ABI specific and while it may be valuable in catching suspicious
   frames is not in the scope of this change.
3) is also an interesting check but thanks to just-in-time compilation
   it's more complex than just calling 
   StackWalker::InstructionAddressSeemsValid() 
   and we don't want to drop parts of the callstack due to an overly
   conservative check.

Bug: chromium:735989

Change-Id: I9aaba77c7fd028942d77c87d51b5e6f94e136ddd
Reviewed-on: https://chromium-review.googlesource.com/563771
Reviewed-by: Mark Mentovai <mark@chromium.org>
Reviewed-by: Ivan Penkov <ivanpe@chromium.org>
2017-07-12 17:53:15 +00:00

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// Copyright (c) 2013 Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// stackwalker_mips.cc: MIPS-specific stackwalker.
//
// See stackwalker_mips.h for documentation.
//
// Author: Tata Elxsi
#include "common/scoped_ptr.h"
#include "google_breakpad/processor/call_stack.h"
#include "google_breakpad/processor/code_modules.h"
#include "google_breakpad/processor/memory_region.h"
#include "google_breakpad/processor/source_line_resolver_interface.h"
#include "google_breakpad/processor/stack_frame_cpu.h"
#include "processor/cfi_frame_info.h"
#include "processor/logging.h"
#include "processor/postfix_evaluator-inl.h"
#include "processor/stackwalker_mips.h"
#include "processor/windows_frame_info.h"
#include "google_breakpad/common/minidump_cpu_mips.h"
namespace google_breakpad {
StackwalkerMIPS::StackwalkerMIPS(const SystemInfo* system_info,
const MDRawContextMIPS* context,
MemoryRegion* memory,
const CodeModules* modules,
StackFrameSymbolizer* resolver_helper)
: Stackwalker(system_info, memory, modules, resolver_helper),
context_(context) {
if (memory_) {
if (context_->context_flags & MD_CONTEXT_MIPS64 ) {
if (0xffffffffffffffff - memory_->GetBase() < memory_->GetSize() - 1) {
BPLOG(ERROR) << "Memory out of range for stackwalking mips64: "
<< HexString(memory_->GetBase())
<< "+"
<< HexString(memory_->GetSize());
memory_ = NULL;
}
} else {
if (0xffffffff - memory_->GetBase() < memory_->GetSize() - 1) {
BPLOG(ERROR) << "Memory out of range for stackwalking mips32: "
<< HexString(memory_->GetBase())
<< "+"
<< HexString(memory_->GetSize());
memory_ = NULL;
}
}
}
}
StackFrame* StackwalkerMIPS::GetContextFrame() {
if (!context_) {
BPLOG(ERROR) << "Can't get context frame without context.";
return NULL;
}
StackFrameMIPS* frame = new StackFrameMIPS();
// The instruction pointer is stored directly in a register, so pull it
// straight out of the CPU context structure.
frame->context = *context_;
frame->context_validity = StackFrameMIPS::CONTEXT_VALID_ALL;
frame->trust = StackFrame::FRAME_TRUST_CONTEXT;
frame->instruction = frame->context.epc;
return frame;
}
// Register names for mips.
static const char* const kRegisterNames[] = {
"$zero", "$at", "$v0", "$v1", "$a0", "$a1", "$a2", "$a3", "$to", "$t1",
"$t2", "$t3", "$t4", "$t5", "$t6", "$t7", "$s0", "$s1", "$s2", "$s3",
"$s4", "$s5", "$s6", "$s7", "$t8", "$t9", "$k0", "$k1", "$gp", "$sp",
"$fp", "$ra", NULL
// TODO(gordanac): add float point save registers
};
StackFrameMIPS* StackwalkerMIPS::GetCallerByCFIFrameInfo(
const vector<StackFrame*>& frames,
CFIFrameInfo* cfi_frame_info) {
StackFrameMIPS* last_frame = static_cast<StackFrameMIPS*>(frames.back());
if (context_->context_flags & MD_CONTEXT_MIPS) {
uint32_t pc = 0;
// Populate a dictionary with the valid register values in last_frame.
CFIFrameInfo::RegisterValueMap<uint32_t> callee_registers;
// Use the STACK CFI data to recover the caller's register values.
CFIFrameInfo::RegisterValueMap<uint32_t> caller_registers;
for (int i = 0; kRegisterNames[i]; ++i) {
caller_registers[kRegisterNames[i]] = last_frame->context.iregs[i];
callee_registers[kRegisterNames[i]] = last_frame->context.iregs[i];
}
if (!cfi_frame_info->FindCallerRegs(callee_registers, *memory_,
&caller_registers)) {
return NULL;
}
CFIFrameInfo::RegisterValueMap<uint32_t>::const_iterator entry =
caller_registers.find(".cfa");
if (entry != caller_registers.end()) {
caller_registers["$sp"] = entry->second;
}
entry = caller_registers.find(".ra");
if (entry != caller_registers.end()) {
caller_registers["$ra"] = entry->second;
pc = entry->second - 2 * sizeof(pc);
}
caller_registers["$pc"] = pc;
// Construct a new stack frame given the values the CFI recovered.
scoped_ptr<StackFrameMIPS> frame(new StackFrameMIPS());
for (int i = 0; kRegisterNames[i]; ++i) {
CFIFrameInfo::RegisterValueMap<uint32_t>::const_iterator caller_entry =
caller_registers.find(kRegisterNames[i]);
if (caller_entry != caller_registers.end()) {
// The value of this register is recovered; fill the context with the
// value from caller_registers.
frame->context.iregs[i] = caller_entry->second;
frame->context_validity |= StackFrameMIPS::RegisterValidFlag(i);
} else if (((i >= INDEX_MIPS_REG_S0 && i <= INDEX_MIPS_REG_S7) ||
(i > INDEX_MIPS_REG_GP && i < INDEX_MIPS_REG_RA)) &&
(last_frame->context_validity &
StackFrameMIPS::RegisterValidFlag(i))) {
// If the STACK CFI data doesn't mention some callee-save register, and
// it is valid in the callee, assume the callee has not yet changed it.
// Calee-save registers according to the MIPS o32 ABI specification are:
// $s0 to $s7
// $sp, $s8
frame->context.iregs[i] = last_frame->context.iregs[i];
frame->context_validity |= StackFrameMIPS::RegisterValidFlag(i);
}
}
frame->context.epc = caller_registers["$pc"];
frame->instruction = caller_registers["$pc"];
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_PC;
frame->context.iregs[MD_CONTEXT_MIPS_REG_RA] = caller_registers["$ra"];
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_RA;
frame->trust = StackFrame::FRAME_TRUST_CFI;
return frame.release();
} else {
uint64_t pc = 0;
// Populate a dictionary with the valid register values in last_frame.
CFIFrameInfo::RegisterValueMap<uint64_t> callee_registers;
// Use the STACK CFI data to recover the caller's register values.
CFIFrameInfo::RegisterValueMap<uint64_t> caller_registers;
for (int i = 0; kRegisterNames[i]; ++i) {
caller_registers[kRegisterNames[i]] = last_frame->context.iregs[i];
callee_registers[kRegisterNames[i]] = last_frame->context.iregs[i];
}
if (!cfi_frame_info->FindCallerRegs(callee_registers, *memory_,
&caller_registers)) {
return NULL;
}
CFIFrameInfo::RegisterValueMap<uint64_t>::const_iterator entry =
caller_registers.find(".cfa");
if (entry != caller_registers.end()) {
caller_registers["$sp"] = entry->second;
}
entry = caller_registers.find(".ra");
if (entry != caller_registers.end()) {
caller_registers["$ra"] = entry->second;
pc = entry->second - 2 * sizeof(pc);
}
caller_registers["$pc"] = pc;
// Construct a new stack frame given the values the CFI recovered.
scoped_ptr<StackFrameMIPS> frame(new StackFrameMIPS());
for (int i = 0; kRegisterNames[i]; ++i) {
CFIFrameInfo::RegisterValueMap<uint64_t>::const_iterator caller_entry =
caller_registers.find(kRegisterNames[i]);
if (caller_entry != caller_registers.end()) {
// The value of this register is recovered; fill the context with the
// value from caller_registers.
frame->context.iregs[i] = caller_entry->second;
frame->context_validity |= StackFrameMIPS::RegisterValidFlag(i);
} else if (((i >= INDEX_MIPS_REG_S0 && i <= INDEX_MIPS_REG_S7) ||
(i >= INDEX_MIPS_REG_GP && i < INDEX_MIPS_REG_RA)) &&
(last_frame->context_validity &
StackFrameMIPS::RegisterValidFlag(i))) {
// If the STACK CFI data doesn't mention some callee-save register, and
// it is valid in the callee, assume the callee has not yet changed it.
// Calee-save registers according to the MIPS o32 ABI specification are:
// $s0 to $s7
// $sp, $s8
frame->context.iregs[i] = last_frame->context.iregs[i];
frame->context_validity |= StackFrameMIPS::RegisterValidFlag(i);
}
}
frame->context.epc = caller_registers["$pc"];
frame->instruction = caller_registers["$pc"];
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_PC;
frame->context.iregs[MD_CONTEXT_MIPS_REG_RA] = caller_registers["$ra"];
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_RA;
frame->trust = StackFrame::FRAME_TRUST_CFI;
return frame.release();
}
}
StackFrame* StackwalkerMIPS::GetCallerFrame(const CallStack* stack,
bool stack_scan_allowed) {
if (!memory_ || !stack) {
BPLOG(ERROR) << "Can't get caller frame without memory or stack";
return NULL;
}
const vector<StackFrame*>& frames = *stack->frames();
StackFrameMIPS* last_frame = static_cast<StackFrameMIPS*>(frames.back());
scoped_ptr<StackFrameMIPS> new_frame;
// See if there is DWARF call frame information covering this address.
scoped_ptr<CFIFrameInfo> cfi_frame_info(
frame_symbolizer_->FindCFIFrameInfo(last_frame));
if (cfi_frame_info.get())
new_frame.reset(GetCallerByCFIFrameInfo(frames, cfi_frame_info.get()));
// If caller frame is not found in CFI try analyzing the stack.
if (stack_scan_allowed && !new_frame.get()) {
new_frame.reset(GetCallerByStackScan(frames));
}
// If nothing worked, tell the caller.
if (!new_frame.get()) {
return NULL;
}
// Should we terminate the stack walk? (end-of-stack or broken invariant)
if (TerminateWalk(new_frame->context.epc,
new_frame->context.iregs[MD_CONTEXT_MIPS_REG_SP],
last_frame->context.iregs[MD_CONTEXT_MIPS_REG_SP],
frames.size() == 1)) {
return NULL;
}
return new_frame.release();
}
StackFrameMIPS* StackwalkerMIPS::GetCallerByStackScan(
const vector<StackFrame*>& frames) {
const uint32_t kMaxFrameStackSize = 1024;
const uint32_t kMinArgsOnStack = 4;
StackFrameMIPS* last_frame = static_cast<StackFrameMIPS*>(frames.back());
if (context_->context_flags & MD_CONTEXT_MIPS) {
uint32_t last_sp = last_frame->context.iregs[MD_CONTEXT_MIPS_REG_SP];
uint32_t caller_pc, caller_sp, caller_fp;
// Return address cannot be obtained directly.
// Force stackwalking.
// We cannot use frame pointer to get the return address.
// We'll scan the stack for a
// return address. This can happen if last_frame is executing code
// for a module for which we don't have symbols.
int count = kMaxFrameStackSize / sizeof(caller_pc);
if (frames.size() > 1) {
// In case of mips32 ABI stack frame of a nonleaf function
// must have minimum stack frame assigned for 4 arguments (4 words).
// Move stack pointer for 4 words to avoid reporting non-existing frames
// for all frames except the topmost one.
// There is no way of knowing if topmost frame belongs to a leaf or
// a nonleaf function.
last_sp += kMinArgsOnStack * sizeof(caller_pc);
// Adjust 'count' so that return address is scanned only in limits
// of one stack frame.
count -= kMinArgsOnStack;
}
do {
// Scanning for return address from stack pointer of the last frame.
if (!ScanForReturnAddress(last_sp, &caller_sp, &caller_pc, count)) {
// If we can't find an instruction pointer even with stack scanning,
// give up.
BPLOG(ERROR) << " ScanForReturnAddress failed ";
return NULL;
}
// Get $fp stored in the stack frame.
if (!memory_->GetMemoryAtAddress(caller_sp - sizeof(caller_pc),
&caller_fp)) {
BPLOG(INFO) << " GetMemoryAtAddress for fp failed " ;
return NULL;
}
count = count - (caller_sp - last_sp) / sizeof(caller_pc);
// Now scan the next address in the stack.
last_sp = caller_sp + sizeof(caller_pc);
} while ((caller_fp - caller_sp >= kMaxFrameStackSize) && count > 0);
if (!count) {
BPLOG(INFO) << " No frame found " ;
return NULL;
}
// ScanForReturnAddress found a reasonable return address. Advance
// $sp to the location above the one where the return address was
// found.
caller_sp += sizeof(caller_pc);
// caller_pc is actually containing $ra value;
// $pc is two instructions before $ra,
// so the caller_pc needs to be decremented accordingly.
caller_pc -= 2 * sizeof(caller_pc);
// Create a new stack frame (ownership will be transferred to the caller)
// and fill it in.
StackFrameMIPS* frame = new StackFrameMIPS();
frame->trust = StackFrame::FRAME_TRUST_SCAN;
frame->context = last_frame->context;
frame->context.epc = caller_pc;
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_PC;
frame->instruction = caller_pc;
frame->context.iregs[MD_CONTEXT_MIPS_REG_SP] = caller_sp;
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_SP;
frame->context.iregs[MD_CONTEXT_MIPS_REG_FP] = caller_fp;
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_FP;
frame->context.iregs[MD_CONTEXT_MIPS_REG_RA] =
caller_pc + 2 * sizeof(caller_pc);
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_RA;
return frame;
} else {
uint64_t last_sp = last_frame->context.iregs[MD_CONTEXT_MIPS_REG_SP];
uint64_t caller_pc, caller_sp, caller_fp;
// Return address cannot be obtained directly.
// Force stackwalking.
// We cannot use frame pointer to get the return address.
// We'll scan the stack for a
// return address. This can happen if last_frame is executing code
// for a module for which we don't have symbols.
int count = kMaxFrameStackSize / sizeof(caller_pc);
do {
// Scanning for return address from stack pointer of the last frame.
if (!ScanForReturnAddress(last_sp, &caller_sp, &caller_pc, count)) {
// If we can't find an instruction pointer even with stack scanning,
// give up.
BPLOG(ERROR) << " ScanForReturnAddress failed ";
return NULL;
}
// Get $fp stored in the stack frame.
if (!memory_->GetMemoryAtAddress(caller_sp - sizeof(caller_pc),
&caller_fp)) {
BPLOG(INFO) << " GetMemoryAtAddress for fp failed " ;
return NULL;
}
count = count - (caller_sp - last_sp) / sizeof(caller_pc);
// Now scan the next address in the stack.
last_sp = caller_sp + sizeof(caller_pc);
} while ((caller_fp - caller_sp >= kMaxFrameStackSize) && count > 0);
if (!count) {
BPLOG(INFO) << " No frame found " ;
return NULL;
}
// ScanForReturnAddress found a reasonable return address. Advance
// $sp to the location above the one where the return address was
// found.
caller_sp += sizeof(caller_pc);
// caller_pc is actually containing $ra value;
// $pc is two instructions before $ra,
// so the caller_pc needs to be decremented accordingly.
caller_pc -= 2 * sizeof(caller_pc);
// Create a new stack frame (ownership will be transferred to the caller)
// and fill it in.
StackFrameMIPS* frame = new StackFrameMIPS();
frame->trust = StackFrame::FRAME_TRUST_SCAN;
frame->context = last_frame->context;
frame->context.epc = caller_pc;
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_PC;
frame->instruction = caller_pc;
frame->context.iregs[MD_CONTEXT_MIPS_REG_SP] = caller_sp;
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_SP;
frame->context.iregs[MD_CONTEXT_MIPS_REG_FP] = caller_fp;
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_FP;
frame->context.iregs[MD_CONTEXT_MIPS_REG_RA] =
caller_pc + 2 * sizeof(caller_pc);
frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_RA;
return frame;
}
}
} // namespace google_breakpad
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