From fd5e35fcb685b6a0b43742b72f6542fd5f80b8fb Mon Sep 17 00:00:00 2001
From: Jeffrey Walton <noloader@gmail.com>
Date: Fri, 30 Nov 2018 05:28:44 -0500
Subject: [PATCH] Fix SIGILL on Linux when using XLC for DARN

---
 ppc_power9.cpp | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/ppc_power9.cpp b/ppc_power9.cpp
index 38c231f5..f4fbd371 100644
--- a/ppc_power9.cpp
+++ b/ppc_power9.cpp
@@ -6,6 +6,14 @@
 //    additional CXXFLAGS are required to enable the appropriate
 //    instructions sets in some build configurations.
 
+// The XLC on Linux case is a special case because code generated by XLC on
+// Linux claims the generator is available when it is not. LLVM Clang does
+// not have the trouble. The problem seems to be related to the signal
+// handler. It looks like first call to CPU_ProbePower9() and CPU_ProbeDARN()
+// are correct, but the call to HasDARN() returns the wrong result. If I am
+// parsing things correctly while stepping the code and disassembly, it looks
+// like the result of the inline asm is being removed.
+
 #include "pch.h"
 #include "config.h"
 
@@ -43,6 +51,8 @@ bool CPU_ProbePower9()
 {
 #if defined(CRYPTOPP_NO_CPU_FEATURE_PROBES)
     return false;
+#elif defined(__xlC__) && defined(__linux__)
+    return false;
 #elif defined(CRYPTOPP_POWER9_AVAILABLE)
 # if defined(CRYPTOPP_GNU_STYLE_INLINE_ASSEMBLY)
     // longjmp and clobber warnings. Volatile is required.
@@ -80,15 +90,18 @@ bool CPU_ProbePower9()
 #endif  // _ARCH_PWR9
 }
 
-// The DARN probe is not guarded with a preprocessor macro at the moment. We don't
-// use CRYPTOPP_POWER9_AVAILABLE because old compilers, like GCC 4.8 on CentOS 7,
-// will report NO even though we can produce the random numbers. Other Power9
-// implementations which use builtins will use the preprocessor macro guard. This
-// strategy also gets into a situation where Power9 is not available but DARN is.
+// The DARN probe is not guarded with a preprocessor macro at the moment. We
+// don't use CRYPTOPP_POWER9_AVAILABLE because old compilers, like GCC 4.8 on
+// CentOS 7, will report NO even though we can produce the random numbers.
+// Other Power9 implementations which use builtins will use the preprocessor
+// macro guard. This strategy also gets into a situation where Power9 is not
+// available but DARN is.
 bool CPU_ProbeDARN()
 {
 #if defined(CRYPTOPP_NO_CPU_FEATURE_PROBES)
     return false;
+#elif defined(__xlC__) && defined(__linux__)
+    return false;
 #else
 # if defined(CRYPTOPP_GNU_STYLE_INLINE_ASSEMBLY)
     // longjmp and clobber warnings. Volatile is required.