From 25f3ce6a509ff9e3a354303023cb2028e9f83b95 Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Tue, 29 Oct 2019 18:59:32 +0000
Subject: [PATCH] base/dispatch.c, etc.: Replace inline assembler for the
 `rdrand' fix.

---
 base/dispatch-x86ish.S   | 43 +++++++++++++++++++++++++++++++++++++++++++
 base/dispatch.c          | 24 +++---------------------
 debian/catacomb2.symbols |  1 +
 3 files changed, 47 insertions(+), 21 deletions(-)

diff --git a/base/dispatch-x86ish.S b/base/dispatch-x86ish.S
index 2c267b62..3e2d4c83 100644
--- a/base/dispatch-x86ish.S
+++ b/base/dispatch-x86ish.S
@@ -153,4 +153,47 @@ FUNC(dispatch_x86ish_xmmregisters_p)
 	ret
 ENDFUNC
 
+///--------------------------------------------------------------------------
+/// Checking `rdrand'.
+
+FUNC(dispatch_x86ish_rdrand)
+	// Enter with one argument: a pointer X_OUT to a 32-bit word.  Try to
+	// generate a random word using `rdrand'.  If successful, set *X_OUT
+	// to the generated word, and return zero; otherwise, return -1.
+
+#if CPUFAM_X86
+#  define X_OUT edx
+#  define COUNT ecx
+	mov	X_OUT, [SP + 4]
+#endif
+#if CPUFAM_AMD64 && ABI_SYSV
+#  define X_OUT rdi
+#  define COUNT ecx
+#endif
+#if CPUFAM_AMD64 && ABI_WIN
+#  define X_OUT rcx
+#  define COUNT edx
+#endif
+  endprologue
+
+	mov	COUNT, 16		// fairly persistent
+0:	rdrand	eax
+	jc	9f
+	dec	COUNT
+	jnz	0b
+
+	// Failed to come up with a random value.
+	mov	eax, -1
+	ret
+
+	// Success.
+9:	mov	[X_OUT], eax
+	xor	eax, eax
+	ret
+
+#undef X_OUT
+#undef COUNT
+
+ENDFUNC
+
 ///----- That's all, folks --------------------------------------------------
diff --git a/base/dispatch.c b/base/dispatch.c
index 459302f0..65ea2d25 100644
--- a/base/dispatch.c
+++ b/base/dispatch.c
@@ -54,6 +54,7 @@
 struct cpuid { unsigned a, b, c, d; };
 extern int dispatch_x86ish_cpuid(struct cpuid *, unsigned a, unsigned c);
 extern int dispatch_x86ish_xmmregisters_p(void);
+extern int dispatch_x86ish_rdrand(unsigned *);
 
 static void cpuid(struct cpuid *cc, unsigned a, unsigned c)
 {
@@ -110,25 +111,6 @@ static int xmm_registers_available_p(void)
  *		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;
@@ -137,9 +119,9 @@ static int rdrand_works_p(void)
    * will fail with probability %$2^{-128}$% with a truly random generator,
    * which seems fair enough.
    */
-  if (rdrand(&ref)) goto fail;
+  if (dispatch_x86ish_rdrand(&ref)) goto fail;
   for (i = 0; i < 4; i++) {
-    if (rdrand(&x)) goto fail;
+    if (dispatch_x86ish_rdrand(&x)) goto fail;
     if (x != ref) goto not_stuck;
   }
   dispatch_debug("RDRAND always returns 0x%08x!", ref);
diff --git a/debian/catacomb2.symbols b/debian/catacomb2.symbols
index 772d218e..33d5915a 100644
--- a/debian/catacomb2.symbols
+++ b/debian/catacomb2.symbols
@@ -24,6 +24,7 @@ libcatacomb.so.2 catacomb2 #MINVER#
 	cpu_feature_p@Base 2.2.3
 	dispatch_debug@Base 2.2.3
 	(optional|arch=i386 amd64)dispatch_x86ish_cpuid@Base 2.5.0
+	(optional|arch=i386 amd64)dispatch_x86ish_rdrand@Base 2.5.99~
 	(optional|arch=i386 amd64)dispatch_x86ish_xmmregisters_p@Base 2.5.0
 
 ## regdump (available with `--enable-asm-debug')
-- 
2.11.0