X-Git-Url: https://git.distorted.org.uk/~mdw/catacomb/blobdiff_plain/25eccdf75b4839dfd3f018f19a81772d7d4350c6..6a024d24d97cb5d42c0091571735475b849f59f4:/base/dispatch.c

diff --git a/base/dispatch.c b/base/dispatch.c
index 50c94380..42c64ee5 100644
--- a/base/dispatch.c
+++ b/base/dispatch.c
@@ -198,6 +198,59 @@ static int xmm_registers_available_p(void)
 #endif
 }
 
+/* --- @rdrand_works_p@ --- *
+ *
+ *
+ * Arguments:	---
+ *
+ * Returns:	Nonzero if the `rdrand' instruction actually works.  Assumes
+ *		that it's already been verified to be safe to issue.
+ */
+
+#ifdef __GNUC__
+static int rdrand(unsigned *x)
+{
+  int i, rc;
+  unsigned _t;
+
+  i = 16;
+  __asm__ ("" : "=g" (_t));
+  __asm__ ("0: rdrand %2; jc 1f; decl %1; jnz 0b\n"
+	   "mov $-1, %0; jmp 9f\n"
+	   "1: movl %2, (%3); xorl %0, %0\n"
+	   "9:"
+	   : "=r" (rc), "+r" (i), "+r" (_t)
+	   : "r" (x)
+	   : "cc");
+  return (rc);
+}
+#endif
+
+static int rdrand_works_p(void)
+{
+  unsigned ref, x, i;
+
+  /* Check that it doesn't always give the same answer.  Try four times: this
+   * will fail with probability %$2^{-128}$% with a truly random generator,
+   * which seems fair enough.
+   */
+  if (rdrand(&ref)) goto fail;
+  for (i = 0; i < 4; i++) {
+    if (rdrand(&x)) goto fail;
+    if (x != ref) goto not_stuck;
+  }
+  dispatch_debug("RDRAND always returns 0x%08x!", ref);
+  return (0);
+
+not_stuck:
+  dispatch_debug("RDRAND instruction looks plausible");
+  return (1);
+
+fail:
+  dispatch_debug("RDRAND instruction fails too often");
+  return (0);
+}
+
 #endif
 
 /*----- General feature probing using auxiliary vectors -------------------*/
@@ -229,6 +282,11 @@ struct auxentry { unsigned long type; union auxval value; };
 #  define WANT_AT_HWCAP(_) _(AT_HWCAP, u, hwcap)
 #endif
 
+#if defined(AT_HWCAP) && CPUFAM_ARM64
+#  define WANT_ANY 1
+#  define WANT_AT_HWCAP(_) _(AT_HWCAP, u, hwcap)
+#endif
+
 #if defined(AT_HWCAP2) && CPUFAM_ARMEL
 #  define WANT_ANY 1
 #  define WANT_AT_HWCAP2(_) _(AT_HWCAP2, u, hwcap2)
@@ -278,6 +336,12 @@ static unsigned hwcaps = 0;
 	_(ARM_D32, "arm:d32")						\
 	_(ARM_AES, "arm:aes")
 #endif
+#if CPUFAM_ARM64
+#  define WANTAUX(_)							\
+	WANT_AT_HWCAP(_)
+#  define CAPMAP(_)							\
+	_(ARM_AES, "arm:aes")
+#endif
 
 /* Build the bitmask for `hwcaps' from the `CAPMAP' list. */
 enum {
@@ -391,6 +455,9 @@ static void probe_hwcaps(void)
   if (probed.hwcap2 & HWCAP2_AES) hw |= HF_ARM_AES;
 #  endif
 #endif
+#if CPUFAM_ARM64
+  if (probed.hwcap & HWCAP_AES) hw |= HF_ARM_AES;
+#endif
 
   /* Store the bitmask of features we probed for everyone to see. */
   DISPATCH_STORE(hwcaps, hw);
@@ -524,13 +591,13 @@ int cpu_feature_p(int feat)
   switch (feat) {
 #if CPUFAM_X86 || CPUFAM_AMD64
     CASE_CPUFEAT(X86_SSE2, "x86:sse2",
-		 xmm_registers_available_p() &&
-		 cpuid_features_p(CPUID1D_SSE2, 0));
+		 cpuid_features_p(CPUID1D_SSE2, 0) &&
+		 xmm_registers_available_p());
     CASE_CPUFEAT(X86_AESNI, "x86:aesni",
-		 xmm_registers_available_p() &&
-		 cpuid_features_p(CPUID1D_SSE2, CPUID1C_AESNI));
+		 cpuid_features_p(CPUID1D_SSE2, CPUID1C_AESNI) &&
+		 xmm_registers_available_p());
     CASE_CPUFEAT(X86_RDRAND, "x86:rdrand",
-		 cpuid_features_p(0, CPUID1C_RDRAND));
+		 cpuid_features_p(0, CPUID1C_RDRAND) && rdrand_works_p());
 #endif
 #ifdef CAPMAP
 #  define FEATP__CASE(feat, tok)					\