Check for RDRAND presence

configure.ac

@@ -506,6 +506,23 @@ __m512i y = _mm512_permutexvar_epi64(_mm512_setr_epi64(0, 1, 4, 5, 2, 3, 6, 7),
     [AC_MSG_RESULT(no)])
   CFLAGS="$oldcflags"
 
+  oldcflags="$CFLAGS"
+  AX_CHECK_COMPILE_FLAG([-mrdrnd], [CFLAGS="$CFLAGS -mrdrnd"])
+  AC_MSG_CHECKING(for RDRAND)
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+#ifdef __native_client__
+# error NativeClient detected - Avoiding RDRAND opcodes
+#endif
+#pragma GCC target("rdrnd")
+#include <immintrin.h>
+]], [[ unsigned long long x; _rdrand64_step(&x); ]])],
+    [AC_MSG_RESULT(yes)
+     AC_DEFINE([HAVE_RDRAND], [1], [rdrand is available])
+     AX_CHECK_COMPILE_FLAG([-mrdrnd], [CFLAGS_RDRAND="-mrdrnd"])
+     ],
+    [AC_MSG_RESULT(no)])
+  CFLAGS="$oldcflags"
+
 ])
 
 AC_SUBST(CFLAGS_MMX)
@@ -518,6 +535,7 @@ AC_SUBST(CFLAGS_AVX2)
 AC_SUBST(CFLAGS_AVX512F)
 AC_SUBST(CFLAGS_AESNI)
 AC_SUBST(CFLAGS_PCLMUL)
+AC_SUBST(CFLAGS_RDRAND)
 
 AC_CHECK_HEADERS([sys/mman.h intrin.h])
 

src/libsodium/Makefile.am

@@ -94,20 +94,6 @@ libsodium_la_SOURCES = \
 	sodium/utils.c \
 	sodium/version.c
 
-if !EMSCRIPTEN
-libsodium_la_SOURCES += \
-	randombytes/salsa20/randombytes_salsa20_random.c
-
-if NATIVECLIENT
-libsodium_la_SOURCES += \
-	randombytes/nativeclient/randombytes_nativeclient.c
-else
-libsodium_la_SOURCES += \
-	randombytes/sysrandom/randombytes_sysrandom.c
-endif
-
-endif
-
 if HAVE_TI_MODE
 libsodium_la_SOURCES += \
 	crypto_core/ed25519/ref10/fe_51/base.h \
@@ -185,6 +171,8 @@ libsodium_la_SOURCES += \
 	crypto_stream/xchacha20/stream_xchacha20.c
 endif
 
+randombytes_salsa20_randombytes_salsa20_random_CFLAGS = @CFLAGS_RDRAND@
+
 libsodium_la_LDFLAGS = \
 	$(AM_LDFLAGS) \
 	-export-dynamic \
@@ -208,7 +196,27 @@ SUBDIRS = \
 	include
 
 libsodium_la_LIBADD = libaesni.la libsse2.la libssse3.la libsse41.la libavx2.la libavx512f.la
-noinst_LTLIBRARIES =  libaesni.la libsse2.la libssse3.la libsse41.la libavx2.la libavx512f.la
+noinst_LTLIBRARIES  = libaesni.la libsse2.la libssse3.la libsse41.la libavx2.la libavx512f.la
+
+librdrand_la_LDFLAGS = $(libsodium_la_LDFLAGS)
+librdrand_la_CPPFLAGS = $(libsodium_la_CPPFLAGS) \
+	@CFLAGS_RDRAND@
+librdrand_la_SOURCES = \
+	randombytes/salsa20/randombytes_salsa20_random.c
+
+if !EMSCRIPTEN
+libsodium_la_LIBADD += librdrand.la
+noinst_LTLIBRARIES  += librdrand.la
+
+if NATIVECLIENT
+libsodium_la_SOURCES += \
+	randombytes/nativeclient/randombytes_nativeclient.c
+else
+libsodium_la_SOURCES += \
+	randombytes/sysrandom/randombytes_sysrandom.c
+endif
+
+endif
 
 libaesni_la_LDFLAGS = $(libsodium_la_LDFLAGS)
 libaesni_la_CPPFLAGS = $(libsodium_la_CPPFLAGS) \

src/libsodium/include/sodium/runtime.h

@@ -38,6 +38,9 @@ int sodium_runtime_has_pclmul(void);
 SODIUM_EXPORT_WEAK
 int sodium_runtime_has_aesni(void);
 
+SODIUM_EXPORT_WEAK
+int sodium_runtime_has_rdrand(void);
+
 /* ------------------------------------------------------------------------- */
 
 int _sodium_runtime_get_cpu_features(void);

src/libsodium/sodium/runtime.c

@@ -19,6 +19,7 @@ typedef struct CPUFeatures_ {
     int has_avx512f;
     int has_pclmul;
     int has_aesni;
+    int has_rdrand;
 } CPUFeatures;
 
 static CPUFeatures _cpu_features;
@@ -34,6 +35,7 @@ static CPUFeatures _cpu_features;
 #define CPUID_ECX_XSAVE   0x04000000
 #define CPUID_ECX_OSXSAVE 0x08000000
 #define CPUID_ECX_AVX     0x10000000
+#define CPUID_ECX_RDRAND  0x40000000
 
 #define CPUID_EDX_SSE2    0x04000000
 
@@ -196,6 +198,12 @@ _sodium_runtime_intel_cpu_features(CPUFeatures * const cpu_features)
     cpu_features->has_aesni  = 0;
 #endif
 
+#ifdef HAVE_RDRAND
+    cpu_features->has_rdrand = ((cpu_info[2] & CPUID_ECX_RDRAND) != 0x0);
+#else
+    cpu_features->has_rdrand = 0;
+#endif
+
     return 0;
 }
 
@@ -270,3 +278,9 @@ sodium_runtime_has_aesni(void)
 {
     return _cpu_features.has_aesni;
 }
+
+int
+sodium_runtime_has_rdrand(void)
+{
+    return _cpu_features.has_rdrand;
+}

test/default/sodium_core.c

@@ -28,6 +28,7 @@ main(void)
     (void) sodium_runtime_has_avx512f();
     (void) sodium_runtime_has_pclmul();
     (void) sodium_runtime_has_aesni();
+    (void) sodium_runtime_has_rdrand();
 
     sodium_set_misuse_handler(misuse_handler);
 #ifndef __EMSCRIPTEN__