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In the AMD64 stackwalker, use heuristics to provide %rbp more often, as

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subsequent frames are usually unable to use CFI if they don't have an %rbp
value.

a=mrmiller, r=jimb


git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@960 4c0a9323-5329-0410-9bdc-e9ce6186880e
This commit is contained in:
jimblandy 2012-04-25 21:11:10 +00:00
parent e6e778f635
commit d1118d6e14
2 changed files with 110 additions and 14 deletions
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37
src/processor/stackwalker_amd64.cc
View file

@ -146,18 +146,13 @@ StackFrameAMD64 *StackwalkerAMD64::GetCallerByStackScan(
const vector<StackFrame *> &frames) {
StackFrameAMD64 *last_frame = static_cast<StackFrameAMD64 *>(frames.back());
u_int64_t last_rsp = last_frame->context.rsp;
u_int64_t caller_rsp, caller_rip;
if (!ScanForReturnAddress(last_rsp, &caller_rsp, &caller_rip)) {
u_int64_t caller_rip_address, caller_rip;
if (!ScanForReturnAddress(last_rsp, &caller_rip_address, &caller_rip)) {
// No plausible return address was found.
return NULL;
}
// ScanForReturnAddress found a reasonable return address. Advance
// %rsp to the location above the one where the return address was
// found.
caller_rsp += 8;
// Create a new stack frame (ownership will be transferred to the caller)
// and fill it in.
StackFrameAMD64 *frame = new StackFrameAMD64();
@ -165,10 +160,34 @@ StackFrameAMD64 *StackwalkerAMD64::GetCallerByStackScan(
frame->trust = StackFrame::FRAME_TRUST_SCAN;
frame->context = last_frame->context;
frame->context.rip = caller_rip;
frame->context.rsp = caller_rsp;
// The caller's %rsp is directly underneath the return address pushed by
// the call.
frame->context.rsp = caller_rip_address + 8;
frame->context_validity = StackFrameAMD64::CONTEXT_VALID_RIP |
StackFrameAMD64::CONTEXT_VALID_RSP;
// Other unwinders give up if they don't have an %rbp value, so see if we
// can pass some plausible value on.
if (last_frame->context_validity & StackFrameAMD64::CONTEXT_VALID_RBP) {
// Functions typically push their caller's %rbp immediately upon entry,
// and then set %rbp to point to that. So if the callee's %rbp is
// pointing to the first word below the alleged return address, presume
// that the caller's %rbp is saved there.
if (caller_rip_address - 8 == last_frame->context.rbp) {
u_int64_t caller_rbp = 0;
if (memory_->GetMemoryAtAddress(last_frame->context.rbp, &caller_rbp) &&
caller_rbp > caller_rip_address) {
frame->context.rbp = caller_rbp;
frame->context_validity |= StackFrameAMD64::CONTEXT_VALID_RBP;
}
} else if (last_frame->context.rbp >= caller_rip_address + 8) {
// If the callee's %rbp is plausible as a value for the caller's
// %rbp, presume that the callee left it unchanged.
frame->context.rbp = last_frame->context.rbp;
frame->context_validity |= StackFrameAMD64::CONTEXT_VALID_RBP;
}
}
return frame;
}

87
src/processor/stackwalker_amd64_unittest.cc
View file

@ -182,7 +182,7 @@ TEST_F(GetCallerFrame, ScanWithoutSymbols) {
stack_section.start() = 0x8000000080000000ULL;
u_int64_t return_address1 = 0x50000000b0000100ULL;
u_int64_t return_address2 = 0x50000000b0000900ULL;
Label frame1_sp, frame2_sp;
Label frame1_sp, frame2_sp, frame1_rbp;
stack_section
// frame 0
.Append(16, 0) // space
@ -198,6 +198,11 @@ TEST_F(GetCallerFrame, ScanWithoutSymbols) {
.D64(0x40000000b0000000ULL) // more junk
.D64(0x50000000d0000000ULL)
.Mark(&frame1_rbp)
.D64(stack_section.start()) // This is in the right place to be
// a saved rbp, but it's bogus, so
// we shouldn't report it.
.D64(return_address2) // actual return address
// frame 2
.Mark(&frame2_sp)
@ -206,6 +211,7 @@ TEST_F(GetCallerFrame, ScanWithoutSymbols) {
RegionFromSection();
raw_context.rip = 0x40000000c0000200ULL;
raw_context.rbp = frame1_rbp.Value();
raw_context.rsp = stack_section.start().Value();
StackwalkerAMD64 walker(&system_info, &raw_context, &stack_region, &modules,
@ -222,10 +228,12 @@ TEST_F(GetCallerFrame, ScanWithoutSymbols) {
StackFrameAMD64 *frame1 = static_cast<StackFrameAMD64 *>(frames->at(1));
EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame1->trust);
ASSERT_EQ((StackFrameAMD64::CONTEXT_VALID_RIP |
StackFrameAMD64::CONTEXT_VALID_RSP),
StackFrameAMD64::CONTEXT_VALID_RSP |
StackFrameAMD64::CONTEXT_VALID_RBP),
frame1->context_validity);
EXPECT_EQ(return_address1, frame1->context.rip);
EXPECT_EQ(frame1_sp.Value(), frame1->context.rsp);
EXPECT_EQ(frame1_rbp.Value(), frame1->context.rbp);
StackFrameAMD64 *frame2 = static_cast<StackFrameAMD64 *>(frames->at(2));
EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame2->trust);
@ -243,7 +251,7 @@ TEST_F(GetCallerFrame, ScanWithFunctionSymbols) {
// lies within a function's bounds.
stack_section.start() = 0x8000000080000000ULL;
u_int64_t return_address = 0x50000000b0000110ULL;
Label frame1_sp;
Label frame1_sp, frame1_rbp;
stack_section
// frame 0
@ -258,10 +266,12 @@ TEST_F(GetCallerFrame, ScanWithFunctionSymbols) {
.D64(return_address) // actual return address
// frame 1
.Mark(&frame1_sp)
.Append(32, 0); // end of stack
.Append(32, 0) // end of stack
.Mark(&frame1_rbp);
RegionFromSection();
raw_context.rip = 0x40000000c0000200ULL;
raw_context.rbp = frame1_rbp.Value();
raw_context.rsp = stack_section.start().Value();
SetModuleSymbols(&module1,
@ -286,14 +296,81 @@ TEST_F(GetCallerFrame, ScanWithFunctionSymbols) {
StackFrameAMD64 *frame1 = static_cast<StackFrameAMD64 *>(frames->at(1));
EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame1->trust);
ASSERT_EQ((StackFrameAMD64::CONTEXT_VALID_RIP |
StackFrameAMD64::CONTEXT_VALID_RSP),
StackFrameAMD64::CONTEXT_VALID_RSP |
StackFrameAMD64::CONTEXT_VALID_RBP),
frame1->context_validity);
EXPECT_EQ(return_address, frame1->context.rip);
EXPECT_EQ(frame1_sp.Value(), frame1->context.rsp);
EXPECT_EQ(frame1_rbp.Value(), frame1->context.rbp);
EXPECT_EQ("echidna", frame1->function_name);
EXPECT_EQ(0x50000000b0000100ULL, frame1->function_base);
}
TEST_F(GetCallerFrame, CallerPushedRBP) {
// Functions typically push their %rbp upon entry and set %rbp pointing
// there. If stackwalking finds a plausible address for the next frame's
// %rbp directly below the return address, assume that it is indeed the
// next frame's %rbp.
stack_section.start() = 0x8000000080000000ULL;
u_int64_t return_address = 0x50000000b0000110ULL;
Label frame0_rbp, frame1_sp, frame1_rbp;
stack_section
// frame 0
.Append(16, 0) // space
.D64(0x40000000b0000000ULL) // junk that's not
.D64(0x50000000b0000000ULL) // a return address
.D64(0x40000000c0001000ULL) // a couple of plausible addresses
.D64(0x50000000b000aaaaULL) // that are not within functions
.Mark(&frame0_rbp)
.D64(frame1_rbp) // caller-pushed %rbp
.D64(return_address) // actual return address
// frame 1
.Mark(&frame1_sp)
.Append(32, 0) // body of frame1
.Mark(&frame1_rbp); // end of stack
RegionFromSection();
raw_context.rip = 0x40000000c0000200ULL;
raw_context.rbp = frame0_rbp.Value();
raw_context.rsp = stack_section.start().Value();
SetModuleSymbols(&module1,
// The youngest frame's function.
"FUNC 100 400 10 sasquatch\n");
SetModuleSymbols(&module2,
// The calling frame's function.
"FUNC 100 400 10 yeti\n");
StackwalkerAMD64 walker(&system_info, &raw_context, &stack_region, &modules,
&supplier, &resolver);
ASSERT_TRUE(walker.Walk(&call_stack));
frames = call_stack.frames();
ASSERT_EQ(2U, frames->size());
StackFrameAMD64 *frame0 = static_cast<StackFrameAMD64 *>(frames->at(0));
EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);
ASSERT_EQ(StackFrameAMD64::CONTEXT_VALID_ALL, frame0->context_validity);
EXPECT_EQ(frame0_rbp.Value(), frame0->context.rbp);
EXPECT_EQ("sasquatch", frame0->function_name);
EXPECT_EQ(0x40000000c0000100ULL, frame0->function_base);
StackFrameAMD64 *frame1 = static_cast<StackFrameAMD64 *>(frames->at(1));
EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame1->trust);
ASSERT_EQ((StackFrameAMD64::CONTEXT_VALID_RIP |
StackFrameAMD64::CONTEXT_VALID_RSP |
StackFrameAMD64::CONTEXT_VALID_RBP),
frame1->context_validity);
EXPECT_EQ(return_address, frame1->context.rip);
EXPECT_EQ(frame1_sp.Value(), frame1->context.rsp);
EXPECT_EQ(frame1_rbp.Value(), frame1->context.rbp);
EXPECT_EQ("yeti", frame1->function_name);
EXPECT_EQ(0x50000000b0000100ULL, frame1->function_base);
}
struct CFIFixture: public StackwalkerAMD64Fixture {
CFIFixture() {
// Provide a bunch of STACK CFI records; we'll walk to the caller