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, 6 insertions, 12 deletions

diff --git a/sha-simd.cpp b/sha-simd.cpp
index 4cf144c8..0dfd733a 100644
--- a/sha-simd.cpp
+++ b/sha-simd.cpp
@@ -61,7 +61,9 @@ extern "C" {
 #if (CRYPTOPP_BOOL_ARM32 || CRYPTOPP_BOOL_ARM64)

 bool CPU_ProbeSHA1()

 {

-#if (CRYPTOPP_ARM_SHA_AVAILABLE)

+#if defined(CRYPTOPP_NO_CPU_FEATURE_PROBES)

+	return false;

+#elif (CRYPTOPP_ARM_SHA_AVAILABLE)

 # if defined(CRYPTOPP_MS_STYLE_INLINE_ASSEMBLY)

     volatile bool result = true;

     __try

@@ -83,11 +85,6 @@ bool CPU_ProbeSHA1()
     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;

@@ -126,7 +123,9 @@ bool CPU_ProbeSHA1()
 

 bool CPU_ProbeSHA2()

 {

-#if (CRYPTOPP_ARM_SHA_AVAILABLE)

+#if defined(CRYPTOPP_NO_CPU_FEATURE_PROBES)

+	return false;

+#elif (CRYPTOPP_ARM_SHA_AVAILABLE)

 # if defined(CRYPTOPP_MS_STYLE_INLINE_ASSEMBLY)

     volatile bool result = true;

     __try

@@ -147,11 +146,6 @@ bool CPU_ProbeSHA2()
     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;