read_cpuid_vals: use __get_cpuid_count() only when availabletmp-fixes

This makes the functionality available on gcc 4.8.

Resolves: #812

Signed-off-by: Nikos Mavrogiannopoulos <nmav@gnutls.org>

2 files changed, 31 insertions, 4 deletions

diff --git a/configure.ac b/configure.ac
index 6a1d3dbc5c..1bf9bce95e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -182,6 +182,17 @@ case $host_cpu in
   ;;
 esac
 
+# check for gcc's __get_cpuid_count functionality
+AC_MSG_CHECKING([for __get_cpuid_count])
+AC_LINK_IFELSE(
+   [AC_LANG_SOURCE([
+    #include <cpuid.h>
+    int main(void) { unsigned t1; return __get_cpuid_count(7, 0, &t1, &t1, &t1, &t1); }
+   ])],
+   [AC_DEFINE([HAVE_GET_CPUID_COUNT], [1], [use __get_cpuid_count]) AC_MSG_RESULT([yes])],
+   [AC_MSG_RESULT([no])]
+)
+
 fi
 
 AC_ARG_ENABLE(tls13-interop,
diff --git a/lib/accelerated/x86/x86-common.c b/lib/accelerated/x86/x86-common.c
index fb3ff90919..516d6776c5 100644
--- a/lib/accelerated/x86/x86-common.c
+++ b/lib/accelerated/x86/x86-common.c
@@ -106,17 +106,33 @@ unsigned int _gnutls_x86_cpuid_s[4];
 #define VIA_PADLOCK_PHE (1<<21)
 #define VIA_PADLOCK_PHE_SHA512 (1<<22)
 
+#ifndef HAVE_GET_CPUID_COUNT
+static inline void
+get_cpuid_level7(unsigned int *eax, unsigned int *ebx,
+		 unsigned int *ecx, unsigned int *edx)
+{
+	/* we avoid using __get_cpuid_count, because it is not available with gcc 4.8 */
+	if (__get_cpuid_max(7, 0) < 7)
+		return;
+
+	__cpuid_count(7, 0, *eax, *ebx, *ecx, *edx);
+	return;
+}
+#else
+# define get_cpuid_level7(a,b,c,d) __get_cpuid_count(7, 0, a, b, c, d)
+#endif
+
 static unsigned read_cpuid_vals(unsigned int vals[4])
 {
 	unsigned t1, t2, t3;
-	if (!__get_cpuid(1, &t1, &vals[0],
-			 &vals[1], &t2))
+	vals[0] = vals[1] = vals[2] = vals[3] = 0;
+
+	if (!__get_cpuid(1, &t1, &vals[0], &vals[1], &t2))
 		return 0;
 	/* suppress AVX512; it works conditionally on certain CPUs on the original code */
 	vals[1] &= 0xfffff7ff;
 
-	if (!__get_cpuid_count(7, 0, &t1, &vals[2], &t2, &t3))
-		return 0;
+	get_cpuid_level7(&t1, &vals[2], &t2, &t3);
 
 	return 1;
 }