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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
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@@ -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;
}