From: Philip Pronin <philipp@fb.com>
Date: Wed, 16 Oct 2013 07:01:53 +0000 (-0700)
Subject: avoid using ifunc + ASan
X-Git-Tag: v0.22.0~813
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=681e46770a9045f8c9c98ae13d3f6205f2be6c85;p=folly.git

avoid using ifunc + ASan

Summary:
Code that is using ifunc dies with SIGSEGV on startup when used
with ASan.

Here is gdb output: {P2882504}

Seems like `ifunc` dispatch is happening before ASan is initialized,
but ASan instrumentation logic being called from there.

Test Plan:
built affected unicorn binaries with ASan, ran them, verified
there is no more SIGSEGV

Reviewed By: meyering@fb.com

FB internal diff: D1013420
---

diff --git a/folly/Bits.cpp b/folly/Bits.cpp
index 15842b45..76ceb0fa 100644
--- a/folly/Bits.cpp
+++ b/folly/Bits.cpp
@@ -17,6 +17,7 @@
 #include "folly/Bits.h"
 
 #include "folly/CpuId.h"
+#include "folly/Portability.h"
 
 // None of this is necessary if we're compiling for a target that supports
 // popcnt
@@ -32,8 +33,7 @@ int popcountll_builtin(unsigned long long x) {
   return __builtin_popcountll(x);
 }
 
-
-#if FOLLY_HAVE_IFUNC
+#if FOLLY_HAVE_IFUNC && !defined(FOLLY_SANITIZE_ADDRESS)
 
 // Strictly speaking, these versions of popcount are usable without ifunc
 // support. However, we would have to check, via CpuId, if the processor
@@ -63,7 +63,7 @@ extern "C" Type_popcountll* folly_popcountll_ifunc() {
   return folly::CpuId().popcnt() ?  popcountll_inst : popcountll_builtin;
 }
 
-#endif // FOLLY_HAVE_IFUNC
+#endif  // FOLLY_HAVE_IFUNC && !defined(FOLLY_SANITIZE_ADDRESS)
 
 }  // namespace
 
@@ -73,7 +73,7 @@ namespace detail {
 // Call folly_popcount_ifunc on startup to resolve to either popcount_inst
 // or popcount_builtin
 int popcount(unsigned int x)
-#if FOLLY_HAVE_IFUNC
+#if FOLLY_HAVE_IFUNC && !defined(FOLLY_SANITIZE_ADDRESS)
   __attribute__((ifunc("folly_popcount_ifunc")));
 #else
 {  return popcount_builtin(x); }
@@ -82,7 +82,7 @@ int popcount(unsigned int x)
 // Call folly_popcount_ifunc on startup to resolve to either popcountll_inst
 // or popcountll_builtin
 int popcountll(unsigned long long x)
-#if FOLLY_HAVE_IFUNC
+#if FOLLY_HAVE_IFUNC && !defined(FOLLY_SANITIZE_ADDRESS)
   __attribute__((ifunc("folly_popcountll_ifunc")));
 #else
 {  return popcountll_builtin(x); }