[scudo] Refactor of CRC32 and ARM runtime CRC32 detection
Summary:
ARM & AArch64 runtime detection for hardware support of CRC32 has been added
via check of the AT_HWVAL auxiliary vector.
Following Michal's suggestions in D28417, the CRC32 code has been further
changed and looks better now. When compiled with full relro (which is strongly
suggested to benefit from additional hardening), the weak symbol for
computeHardwareCRC32 is read-only and the assembly generated is fairly clean
and straight forward. As suggested, an additional optimization is to skip
the runtime check if SSE 4.2 has been enabled globally, as opposed to only
for scudo_crc32.cpp.
scudo_crc32.h has no purpose anymore and was removed.
Reviewers: alekseyshl, kcc, rengolin, mgorny, phosek
Reviewed By: rengolin, mgorny
Subscribers: aemerson, rengolin, llvm-commits
Differential Revision: https://reviews.llvm.org/D28574
llvm-svn: 292409
diff --git a/compiler-rt/lib/scudo/scudo_utils.cpp b/compiler-rt/lib/scudo/scudo_utils.cpp
index 7414408..4e2f6e0 100644
--- a/compiler-rt/lib/scudo/scudo_utils.cpp
+++ b/compiler-rt/lib/scudo/scudo_utils.cpp
@@ -20,8 +20,9 @@
#if defined(__x86_64__) || defined(__i386__)
# include <cpuid.h>
#endif
-
-#include <cstring>
+#if defined(__arm__) || defined(__aarch64__)
+# include <sys/auxv.h>
+#endif
// TODO(kostyak): remove __sanitizer *Printf uses in favor for our own less
// complicated string formatting code. The following is a
@@ -82,7 +83,7 @@
}
#ifndef bit_SSE4_2
-#define bit_SSE4_2 bit_SSE42 // clang and gcc have different defines.
+# define bit_SSE4_2 bit_SSE42 // clang and gcc have different defines.
#endif
bool testCPUFeature(CPUFeature Feature)
@@ -97,6 +98,25 @@
}
return false;
}
+#elif defined(__arm__) || defined(__aarch64__)
+// For ARM and AArch64, hardware CRC32 support is indicated in the
+// AT_HWVAL auxiliary vector.
+
+#ifndef HWCAP_CRC32
+# define HWCAP_CRC32 (1<<7) // HWCAP_CRC32 is missing on older platforms.
+#endif
+
+bool testCPUFeature(CPUFeature Feature) {
+ uptr HWCap = getauxval(AT_HWCAP);
+
+ switch (Feature) {
+ case CRC32CPUFeature:
+ return !!(HWCap & HWCAP_CRC32);
+ default:
+ break;
+ }
+ return false;
+}
#else
bool testCPUFeature(CPUFeature Feature) {
return false;