Add CRYPTOPP_NO_CPU_FEATURE_PROBES (GH #511)

We determine machine capabilities by performing an os/platform *query* first, like getauxv(). If the *query* fails, we move onto a cpu *probe*. The cpu *probe* tries to exeute an instruction and then catches a SIGILL on Linux or the exception EXCEPTION_ILLEGAL_INSTRUCTION on Windows. Some OSes fail to hangle a SIGILL gracefully, like Apple OSes. Apple machines corrupt memory and variables around the probe.

1 files changed, 3 insertions, 6 deletions

diff --git a/crc-simd.cpp b/crc-simd.cpp
index 67ab460f..5a7e77d2 100644
--- a/crc-simd.cpp
+++ b/crc-simd.cpp
@@ -56,7 +56,9 @@ extern "C" {
 

 bool CPU_ProbeCRC32()

 {

-#if (CRYPTOPP_ARM_CRC32_AVAILABLE)

+#if defined(CRYPTOPP_NO_CPU_FEATURE_PROBES)

+	return false;

+#elif (CRYPTOPP_ARM_CRC32_AVAILABLE)

 # if defined(CRYPTOPP_MS_STYLE_INLINE_ASSEMBLY)

     volatile bool result = true;

     __try

@@ -78,11 +80,6 @@ bool CPU_ProbeCRC32()
     return result;

 #else

 

-# if defined(__APPLE__)

-    // No SIGILL probes on Apple platforms.

-    return false;

-# endif

-

     // longjmp and clobber warnings. Volatile is required.

     // http://github.com/weidai11/cryptopp/issues/24 and http://stackoverflow.com/q/7721854

     volatile bool result = true;