[Webkit-unassigned] [Bug 205050] New: Fix the x86_64 probe so that we can get a full stack trace with libunwind and lldb.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=205050

            Bug ID: 205050
           Summary: Fix the x86_64 probe so that we can get a full stack
                    trace with libunwind and lldb.
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: mark.lam at apple.com

Before this patch, the stack trace from inside a probe function is cut off at ctiMasmProbeTrampoline:

    (lldb) bt
    * thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0xbbadbeef)
        ...
        frame #4: 0x0000000100824607 JavaScriptCore`WTF::Function<void (JSC::Probe::Context&)>::operator(this=0x000000010b88bd00, in=0x00007ffeefbfd400)(JSC::Probe::Context&) const at Function.h:79:35
        frame #5: 0x0000000100823996 JavaScriptCore`JSC::stdFunctionCallback(context=0x00007ffeefbfd400) at MacroAssembler.cpp:53:5
        frame #6: 0x000000010082701e JavaScriptCore`JSC::Probe::executeProbe(state=0x00007ffeefbfd480) at ProbeContext.cpp:51:5
        frame #7: 0x000000010082614b JavaScriptCore`ctiMasmProbeTrampoline + 299
    (lldb) 

After this patch, we'll now get the full stack trace from inside the probe function:

    (lldb) bt
    * thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0xbbadbeef)
        ...
        frame #4: 0x0000000100826d17 JavaScriptCore`WTF::Function<void (JSC::Probe::Context&)>::operator(this=0x0000000106b878f8, in=0x00007ffeefbfd400)(JSC::Probe::Context&) const at Function.h:79:35
        frame #5: 0x0000000100826106 JavaScriptCore`JSC::stdFunctionCallback(context=0x00007ffeefbfd400) at MacroAssembler.cpp:53:5
        frame #6: 0x000000010082986e JavaScriptCore`JSC::Probe::executeProbe(state=0x00007ffeefbfd480) at ProbeContext.cpp:51:5
        frame #7: 0x00000001008289a2 JavaScriptCore`ctiMasmProbeTrampoline + 338
        frame #8: 0x0000466db28025be
        frame #9: 0x0000000100754ffc JavaScriptCore`llint_entry at LowLevelInterpreter.asm:994
        frame #10: 0x0000000100738173 JavaScriptCore`vmEntryToJavaScript at LowLevelInterpreter64.asm:307
        frame #11: 0x0000000101489307 JavaScriptCore`JSC::JITCode::execute(this=0x0000000106ba1520, vm=0x0000000106d00000, protoCallFrame=0x00007ffeefbfd9b8) at JITCodeInlines.h:38:38
        frame #12: 0x0000000101488982 JavaScriptCore`JSC::Interpreter::executeProgram(this=0x0000000106bfd1f8, source=0x00007ffeefbff090, (null)=0x000000010d0e0000, thisObj=0x000000010d0e8020) at Interpreter.cpp:847:51
        frame #13: 0x00000001017d1f9c JavaScriptCore`JSC::evaluate(globalObject=0x000000010d0e0000, source=0x00007ffeefbff090, thisValue=JSValue @ 0x00007ffeefbfef60, returnedException=0x00007ffeefbff0b0) at Completion.cpp:146:38
        frame #14: 0x000000010005838f jsc`runWithOptions(globalObject=0x000000010d0e0000, options=0x00007ffeefbff620, success=0x00007ffeefbff48b) at jsc.cpp:2670:35
        frame #15: 0x000000010002a0da jsc`jscmain(this=0x00007ffeefbff5a0, vm=0x0000000106d00000, globalObject=0x000000010d0e0000, success=0x00007ffeefbff48b)::$_6::operator()(JSC::VM&, GlobalObject*, bool&) const at jsc.cpp:3157:13
        frame #16: 0x0000000100006eff jsc`int runJSC<jscmain(int, char**)::$_6>(options=0x00007ffeefbff620, isWorker=false, func=0x00007ffeefbff5a0)::$_6 const&) at jsc.cpp:3003:9
        frame #17: 0x0000000100005988 jsc`jscmain(argc=10, argv=0x00007ffeefbff6c8) at jsc.cpp:3150:18
        frame #18: 0x000000010000575e jsc`main(argc=10, argv=0x00007ffeefbff6c8) at jsc.cpp:2498:15
        frame #19: 0x00007fff6cfc4da9 libdyld.dylib`start + 1
        frame #20: 0x00007fff6cfc4da9 libdyld.dylib`start + 1
    (lldb)

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