[XRay][compiler-rt] Return the pointer associated with the function i…

…nstead of the sled

Summary:
XRay has erroneously been returning the address of the first sled in the
instrumentation map for a function id instead of the (runtime-relocated)
functison address. This causes confusion and issues for applications
where:

  - The first sled in the function may not be an entry sled (due to
    re-ordering or some other reason).
  - The caller attempts to find a symbol associated with the pointer at
    runtime, because the sled may not be exactly where the function's
    known address is (in case of inlined functions or those that have an
    external definition for symbols).

This fixes http://llvm.org/PR34340.

Reviewers: eizan

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D37202

llvm-svn: 311871

compiler-rt/lib/xray/xray_interface.cc

@@ -331,7 +331,7 @@ uintptr_t __xray_function_address(int32_t FuncId) XRAY_NEVER_INSTRUMENT {
   __sanitizer::SpinMutexLock Guard(&XRayInstrMapMutex);
   if (FuncId <= 0 || static_cast<size_t>(FuncId) > XRayInstrMap.Functions)
     return 0;
-  return XRayInstrMap.SledsIndex[FuncId - 1].Begin->Address
+  return XRayInstrMap.SledsIndex[FuncId - 1].Begin->Function
 // On PPC, function entries are always aligned to 16 bytes. The beginning of a
 // sled might be a local entry, which is always +8 based on the global entry.
 // Always return the global entry.