[compiler-rt] 993555b - [compiler-rt][scudo] Check for failing prctl call

[Leonard Chan via llvm-commits]

Author: Leonard Chan
Date: 2021-10-04T13:14:20-07:00
New Revision: 993555beb8ff33aa35773af01cb3821ae45e6e39

URL: https://github.com/llvm/llvm-project/commit/993555beb8ff33aa35773af01cb3821ae45e6e39
DIFF: https://github.com/llvm/llvm-project/commit/993555beb8ff33aa35773af01cb3821ae45e6e39.diff

LOG: [compiler-rt][scudo] Check for failing prctl call

A bunch of MTE tests like ./ScudoUnitTest-aarch64-Test/MemtagTest.StoreTags
can fail on aarch64-linux if the kernel doesn't support the tagged address ABI. It looks like
the call to prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0) can return -1, which
casted to an unsigned int and masked will return a value not equal to
PR_MTE_TCF_NONE, meaning systemDetectsMemoryTagFaultsTestOnly can return an incorrect value.

This updates the check to account for a failing prctl call.

Differential Revision: https://reviews.llvm.org/D110888

Added: 
    

Modified: 
    compiler-rt/lib/scudo/standalone/memtag.h

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/scudo/standalone/memtag.h b/compiler-rt/lib/scudo/standalone/memtag.h
index c48e228fbe44f..8097b77ebd416 100644
--- a/compiler-rt/lib/scudo/standalone/memtag.h
+++ b/compiler-rt/lib/scudo/standalone/memtag.h
@@ -91,9 +91,10 @@ inline bool systemDetectsMemoryTagFaultsTestOnly() {
 #ifndef PR_MTE_TCF_MASK
 #define PR_MTE_TCF_MASK (3UL << PR_MTE_TCF_SHIFT)
 #endif
-  return (static_cast<unsigned long>(
-              prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0)) &
-          PR_MTE_TCF_MASK) != PR_MTE_TCF_NONE;
+  int res = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
+  if (res == -1)
+    return false;
+  return (static_cast<unsigned long>(res) & PR_MTE_TCF_MASK) != PR_MTE_TCF_NONE;
 }
 
 inline void enableSystemMemoryTaggingTestOnly() {