[PATCH] D53040: [libFuzzer] Generalize the code for getting the previous offset for different architectures

[George Karpenkov via Phabricator via llvm-commits]

george.karpenkov created this revision.
george.karpenkov added reviewers: kubamracek, kcc, morehouse.
george.karpenkov added a project: Sanitizers.
Herald added subscribers: Sanitizers, fedor.sergeev.

Without this change, tests in coverage.test and dump_coverage.test are failing on non-x86_64 platforms.
The diff is copied from sanitizer_common library, an alternative would be to link it together with libFuzzer.


Repository:
  rCRT Compiler Runtime

https://reviews.llvm.org/D53040

Files:
  compiler-rt/lib/fuzzer/FuzzerTracePC.cpp


Index: compiler-rt/lib/fuzzer/FuzzerTracePC.cpp
===================================================================
--- compiler-rt/lib/fuzzer/FuzzerTracePC.cpp
+++ compiler-rt/lib/fuzzer/FuzzerTracePC.cpp
@@ -239,15 +239,30 @@
 }
 
 inline ALWAYS_INLINE uintptr_t GetPreviousInstructionPc(uintptr_t PC) {
-  // TODO: this implementation is x86 only.
-  // see sanitizer_common GetPreviousInstructionPc for full implementation.
+#if defined(__arm__)
+  // T32 (Thumb) branch instructions might be 16 or 32 bit long,
+  // so we return (pc-2) in that case in order to be safe.
+  // For A32 mode we return (pc-4) because all instructions are 32 bit long.
+  return (PC - 3) & (~1);
+#elif defined(__powerpc__) || defined(__powerpc64__) || defined(__aarch64__)
+  // PCs are always 4 byte aligned.
+  return PC - 4;
+#elif defined(__sparc__) || defined(__mips__)
+  return PC - 8;
+#else
   return PC - 1;
+#endif
 }
 
 inline ALWAYS_INLINE uintptr_t GetNextInstructionPc(uintptr_t PC) {
-  // TODO: this implementation is x86 only.
-  // see sanitizer_common GetPreviousInstructionPc for full implementation.
+#if defined(__mips__)
+  return PC + 8;
+#elif defined(__powerpc__) || defined(__sparc__) || defined(__arm__) || \
+    defined(__aarch64__)
+  return PC + 4;
+#else
   return PC + 1;
+#endif
 }
 
 static std::string GetModuleName(uintptr_t PC) {


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