curve25519-x86_64: avoid use of r12

This causes problems with RAP and KERNEXEC for PaX, as r12 is a
reserved register.

It also leads to a more compact instruction encoding, saving about 100
cycles.

Suggested-by: PaX Team <pageexec@freemail.hu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 55 insertions, 55 deletions

diff --git a/src/crypto/zinc/curve25519/curve25519-x86_64.c b/src/crypto/zinc/curve25519/curve25519-x86_64.c
index 74570cb..79716c4 100644
--- a/src/crypto/zinc/curve25519/curve25519-x86_64.c
+++ b/src/crypto/zinc/curve25519/curve25519-x86_64.c
@@ -156,28 +156,28 @@ static inline void fmul(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
 		"  movq 0(%1), %%rdx;"
 		"  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  movq %%r8, 0(%0);"
 		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  movq %%r10, 8(%0);"
-		"  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"
+		"  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"
 		"  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"
 		/* Compute src1[1] * src2 */
 		"  movq 8(%1), %%rdx;"
 		"  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  adcxq 8(%0), %%r8;"    "  movq %%r8, 8(%0);"
-		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 16(%0);"
-		"  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 16(%0);"
+		"  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
 		"  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
 		/* Compute src1[2] * src2 */
 		"  movq 16(%1), %%rdx;"
 		"  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 16(%0), %%r8;"    "  movq %%r8, 16(%0);"
-		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 24(%0);"
-		"  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 24(%0);"
+		"  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
 		"  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
 		/* Compute src1[3] * src2 */
 		"  movq 24(%1), %%rdx;"
 		"  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 24(%0), %%r8;"    "  movq %%r8, 24(%0);"
-		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 32(%0);"
-		"  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  movq %%r12, 40(%0);"    "  mov $0, %%r8;"
+		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 32(%0);"
+		"  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  movq %%rbx, 40(%0);"    "  mov $0, %%r8;"
 		"  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  movq %%r14, 48(%0);"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"     "  movq %%rax, 56(%0);"
 		/* Line up pointers */
@@ -191,11 +191,11 @@ static inline void fmul(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
 		"  mulxq 32(%1), %%r8, %%r13;"
 		"  xor %3, %3;"
 		"  adoxq 0(%1), %%r8;"
-		"  mulxq 40(%1), %%r9, %%r12;"
+		"  mulxq 40(%1), %%r9, %%rbx;"
 		"  adcx %%r13, %%r9;"
 		"  adoxq 8(%1), %%r9;"
 		"  mulxq 48(%1), %%r10, %%r13;"
-		"  adcx %%r12, %%r10;"
+		"  adcx %%rbx, %%r10;"
 		"  adoxq 16(%1), %%r10;"
 		"  mulxq 56(%1), %%r11, %%rax;"
 		"  adcx %%r13, %%r11;"
@@ -220,7 +220,7 @@ static inline void fmul(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
 		"  movq %%r8, 0(%0);"
 	: "+&r" (tmp), "+&r" (f1), "+&r" (out), "+&r" (f2)
 	:
-	: "%rax", "%rdx", "%r8", "%r9", "%r10", "%r11", "%r12", "%r13", "%r14", "memory", "cc"
+	: "%rax", "%rdx", "%r8", "%r9", "%r10", "%r11", "%rbx", "%r13", "%r14", "memory", "cc"
 	);
 }
 
@@ -237,28 +237,28 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
 		"  movq 0(%1), %%rdx;"
 		"  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  movq %%r8, 0(%0);"
 		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  movq %%r10, 8(%0);"
-		"  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"
+		"  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"
 		"  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"
 		/* Compute src1[1] * src2 */
 		"  movq 8(%1), %%rdx;"
 		"  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  adcxq 8(%0), %%r8;"    "  movq %%r8, 8(%0);"
-		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 16(%0);"
-		"  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 16(%0);"
+		"  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
 		"  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
 		/* Compute src1[2] * src2 */
 		"  movq 16(%1), %%rdx;"
 		"  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 16(%0), %%r8;"    "  movq %%r8, 16(%0);"
-		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 24(%0);"
-		"  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 24(%0);"
+		"  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
 		"  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
 		/* Compute src1[3] * src2 */
 		"  movq 24(%1), %%rdx;"
 		"  mulxq 0(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 24(%0), %%r8;"    "  movq %%r8, 24(%0);"
-		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 32(%0);"
-		"  mulxq 16(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  movq %%r12, 40(%0);"    "  mov $0, %%r8;"
+		"  mulxq 8(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 32(%0);"
+		"  mulxq 16(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  movq %%rbx, 40(%0);"    "  mov $0, %%r8;"
 		"  mulxq 24(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  movq %%r14, 48(%0);"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"     "  movq %%rax, 56(%0);"
 
@@ -268,28 +268,28 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
 		"  movq 32(%1), %%rdx;"
 		"  mulxq 32(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  movq %%r8, 64(%0);"
 		"  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  movq %%r10, 72(%0);"
-		"  mulxq 48(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"
+		"  mulxq 48(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"
 		"  mulxq 56(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"
 		/* Compute src1[1] * src2 */
 		"  movq 40(%1), %%rdx;"
 		"  mulxq 32(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"     "  adcxq 72(%0), %%r8;"    "  movq %%r8, 72(%0);"
-		"  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 80(%0);"
-		"  mulxq 48(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+		"  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 80(%0);"
+		"  mulxq 48(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
 		"  mulxq 56(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
 		/* Compute src1[2] * src2 */
 		"  movq 48(%1), %%rdx;"
 		"  mulxq 32(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 80(%0), %%r8;"    "  movq %%r8, 80(%0);"
-		"  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 88(%0);"
-		"  mulxq 48(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  mov $0, %%r8;"
+		"  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 88(%0);"
+		"  mulxq 48(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  mov $0, %%r8;"
 		"  mulxq 56(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"
 		/* Compute src1[3] * src2 */
 		"  movq 56(%1), %%rdx;"
 		"  mulxq 32(%3), %%r8, %%r9;"       "  xor %%r10, %%r10;"    "  adcxq 88(%0), %%r8;"    "  movq %%r8, 88(%0);"
-		"  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%r12, %%r10;"    "  movq %%r10, 96(%0);"
-		"  mulxq 48(%3), %%r12, %%r13;"    "  adox %%r11, %%r12;"    "  adcx %%r14, %%r12;"    "  movq %%r12, 104(%0);"    "  mov $0, %%r8;"
+		"  mulxq 40(%3), %%r10, %%r11;"     "  adox %%r9, %%r10;"     "  adcx %%rbx, %%r10;"    "  movq %%r10, 96(%0);"
+		"  mulxq 48(%3), %%rbx, %%r13;"    "  adox %%r11, %%rbx;"    "  adcx %%r14, %%rbx;"    "  movq %%rbx, 104(%0);"    "  mov $0, %%r8;"
 		"  mulxq 56(%3), %%r14, %%rdx;"    "  adox %%r13, %%r14;"    "  adcx %%rax, %%r14;"    "  movq %%r14, 112(%0);"    "  mov $0, %%rax;"
 		                                   "  adox %%rdx, %%rax;"    "  adcx %%r8, %%rax;"     "  movq %%rax, 120(%0);"
 		/* Line up pointers */
@@ -303,11 +303,11 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
 		"  mulxq 32(%1), %%r8, %%r13;"
 		"  xor %3, %3;"
 		"  adoxq 0(%1), %%r8;"
-		"  mulxq 40(%1), %%r9, %%r12;"
+		"  mulxq 40(%1), %%r9, %%rbx;"
 		"  adcx %%r13, %%r9;"
 		"  adoxq 8(%1), %%r9;"
 		"  mulxq 48(%1), %%r10, %%r13;"
-		"  adcx %%r12, %%r10;"
+		"  adcx %%rbx, %%r10;"
 		"  adoxq 16(%1), %%r10;"
 		"  mulxq 56(%1), %%r11, %%rax;"
 		"  adcx %%r13, %%r11;"
@@ -336,11 +336,11 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
 		"  mulxq 96(%1), %%r8, %%r13;"
 		"  xor %3, %3;"
 		"  adoxq 64(%1), %%r8;"
-		"  mulxq 104(%1), %%r9, %%r12;"
+		"  mulxq 104(%1), %%r9, %%rbx;"
 		"  adcx %%r13, %%r9;"
 		"  adoxq 72(%1), %%r9;"
 		"  mulxq 112(%1), %%r10, %%r13;"
-		"  adcx %%r12, %%r10;"
+		"  adcx %%rbx, %%r10;"
 		"  adoxq 80(%1), %%r10;"
 		"  mulxq 120(%1), %%r11, %%rax;"
 		"  adcx %%r13, %%r11;"
@@ -365,7 +365,7 @@ static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
 		"  movq %%r8, 32(%0);"
 	: "+&r" (tmp), "+&r" (f1), "+&r" (out), "+&r" (f2)
 	:
-	: "%rax", "%rdx", "%r8", "%r9", "%r10", "%r11", "%r12", "%r13", "%r14", "memory", "cc"
+	: "%rax", "%rdx", "%r8", "%r9", "%r10", "%r11", "%rbx", "%r13", "%r14", "memory", "cc"
 	);
 }
 
@@ -377,11 +377,11 @@ static inline void fmul_scalar(u64 *out, const u64 *f1, u64 f2)
 	asm volatile(
 		/* Compute the raw multiplication of f1*f2 */
 		"  mulxq 0(%2), %%r8, %%rcx;"      /* f1[0]*f2 */
-		"  mulxq 8(%2), %%r9, %%r12;"      /* f1[1]*f2 */
+		"  mulxq 8(%2), %%r9, %%rbx;"      /* f1[1]*f2 */
 		"  add %%rcx, %%r9;"
 		"  mov $0, %%rcx;"
 		"  mulxq 16(%2), %%r10, %%r13;"    /* f1[2]*f2 */
-		"  adcx %%r12, %%r10;"
+		"  adcx %%rbx, %%r10;"
 		"  mulxq 24(%2), %%r11, %%rax;"    /* f1[3]*f2 */
 		"  adcx %%r13, %%r11;"
 		"  adcx %%rcx, %%rax;"
@@ -408,7 +408,7 @@ static inline void fmul_scalar(u64 *out, const u64 *f1, u64 f2)
 		"  movq %%r8, 0(%1);"
 	: "+&r" (f2_r)
 	: "r" (out), "r" (f1)
-	: "%rax", "%rcx", "%r8", "%r9", "%r10", "%r11", "%r12", "%r13", "memory", "cc"
+	: "%rax", "%rcx", "%r8", "%r9", "%r10", "%r11", "%rbx", "%r13", "memory", "cc"
 	);
 }
 
@@ -509,8 +509,8 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp)
 		"  mulxq 16(%1), %%r9, %%r10;"     "  adcx %%r14, %%r9;"     /* f[2]*f[0] */
 		"  mulxq 24(%1), %%rax, %%rcx;"    "  adcx %%rax, %%r10;"    /* f[3]*f[0] */
 		"  movq 24(%1), %%rdx;"                                      /* f[3] */
-		"  mulxq 8(%1), %%r11, %%r12;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
-		"  mulxq 16(%1), %%rax, %%r13;"    "  adcx %%rax, %%r12;"    /* f[2]*f[3] */
+		"  mulxq 8(%1), %%r11, %%rbx;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
+		"  mulxq 16(%1), %%rax, %%r13;"    "  adcx %%rax, %%rbx;"    /* f[2]*f[3] */
 		"  movq 8(%1), %%rdx;"             "  adcx %%r15, %%r13;"    /* f1 */
 		"  mulxq 16(%1), %%rax, %%rcx;"    "  mov $0, %%r14;"        /* f[2]*f[1] */
 
@@ -520,12 +520,12 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp)
 		"  adcx %%r8, %%r8;"
 		"  adox %%rcx, %%r11;"
 		"  adcx %%r9, %%r9;"
-		"  adox %%r15, %%r12;"
+		"  adox %%r15, %%rbx;"
 		"  adcx %%r10, %%r10;"
 		"  adox %%r15, %%r13;"
 		"  adcx %%r11, %%r11;"
 		"  adox %%r15, %%r14;"
-		"  adcx %%r12, %%r12;"
+		"  adcx %%rbx, %%rbx;"
 		"  adcx %%r13, %%r13;"
 		"  adcx %%r14, %%r14;"
 
@@ -538,7 +538,7 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp)
 		"  adcx %%rcx, %%r10;"     "  movq %%r10, 24(%0);"
 		"  movq 16(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[2]^2 */
 		"  adcx %%rax, %%r11;"     "  movq %%r11, 32(%0);"
-		"  adcx %%rcx, %%r12;"     "  movq %%r12, 40(%0);"
+		"  adcx %%rcx, %%rbx;"     "  movq %%rbx, 40(%0);"
 		"  movq 24(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[3]^2 */
 		"  adcx %%rax, %%r13;"     "  movq %%r13, 48(%0);"
 		"  adcx %%rcx, %%r14;"     "  movq %%r14, 56(%0);"
@@ -554,11 +554,11 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp)
 		"  mulxq 32(%1), %%r8, %%r13;"
 		"  xor %%rcx, %%rcx;"
 		"  adoxq 0(%1), %%r8;"
-		"  mulxq 40(%1), %%r9, %%r12;"
+		"  mulxq 40(%1), %%r9, %%rbx;"
 		"  adcx %%r13, %%r9;"
 		"  adoxq 8(%1), %%r9;"
 		"  mulxq 48(%1), %%r10, %%r13;"
-		"  adcx %%r12, %%r10;"
+		"  adcx %%rbx, %%r10;"
 		"  adoxq 16(%1), %%r10;"
 		"  mulxq 56(%1), %%r11, %%rax;"
 		"  adcx %%r13, %%r11;"
@@ -583,7 +583,7 @@ static inline void fsqr(u64 *out, const u64 *f, u64 *tmp)
 		"  movq %%r8, 0(%0);"
 	: "+&r" (tmp), "+&r" (f), "+&r" (out)
 	:
-	: "%rax", "%rcx", "%rdx", "%r8", "%r9", "%r10", "%r11", "%r12", "%r13", "%r14", "%r15", "memory", "cc"
+	: "%rax", "%rcx", "%rdx", "%r8", "%r9", "%r10", "%r11", "%rbx", "%r13", "%r14", "%r15", "memory", "cc"
 	);
 }
 
@@ -600,8 +600,8 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
 		"  mulxq 16(%1), %%r9, %%r10;"     "  adcx %%r14, %%r9;"     /* f[2]*f[0] */
 		"  mulxq 24(%1), %%rax, %%rcx;"    "  adcx %%rax, %%r10;"    /* f[3]*f[0] */
 		"  movq 24(%1), %%rdx;"                                      /* f[3] */
-		"  mulxq 8(%1), %%r11, %%r12;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
-		"  mulxq 16(%1), %%rax, %%r13;"    "  adcx %%rax, %%r12;"    /* f[2]*f[3] */
+		"  mulxq 8(%1), %%r11, %%rbx;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
+		"  mulxq 16(%1), %%rax, %%r13;"    "  adcx %%rax, %%rbx;"    /* f[2]*f[3] */
 		"  movq 8(%1), %%rdx;"             "  adcx %%r15, %%r13;"    /* f1 */
 		"  mulxq 16(%1), %%rax, %%rcx;"    "  mov $0, %%r14;"        /* f[2]*f[1] */
 
@@ -611,12 +611,12 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
 		"  adcx %%r8, %%r8;"
 		"  adox %%rcx, %%r11;"
 		"  adcx %%r9, %%r9;"
-		"  adox %%r15, %%r12;"
+		"  adox %%r15, %%rbx;"
 		"  adcx %%r10, %%r10;"
 		"  adox %%r15, %%r13;"
 		"  adcx %%r11, %%r11;"
 		"  adox %%r15, %%r14;"
-		"  adcx %%r12, %%r12;"
+		"  adcx %%rbx, %%rbx;"
 		"  adcx %%r13, %%r13;"
 		"  adcx %%r14, %%r14;"
 
@@ -629,7 +629,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
 		"  adcx %%rcx, %%r10;"     "  movq %%r10, 24(%0);"
 		"  movq 16(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[2]^2 */
 		"  adcx %%rax, %%r11;"     "  movq %%r11, 32(%0);"
-		"  adcx %%rcx, %%r12;"     "  movq %%r12, 40(%0);"
+		"  adcx %%rcx, %%rbx;"     "  movq %%rbx, 40(%0);"
 		"  movq 24(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[3]^2 */
 		"  adcx %%rax, %%r13;"     "  movq %%r13, 48(%0);"
 		"  adcx %%rcx, %%r14;"     "  movq %%r14, 56(%0);"
@@ -640,8 +640,8 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
 		"  mulxq 48(%1), %%r9, %%r10;"     "  adcx %%r14, %%r9;"     /* f[2]*f[0] */
 		"  mulxq 56(%1), %%rax, %%rcx;"    "  adcx %%rax, %%r10;"    /* f[3]*f[0] */
 		"  movq 56(%1), %%rdx;"                                      /* f[3] */
-		"  mulxq 40(%1), %%r11, %%r12;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
-		"  mulxq 48(%1), %%rax, %%r13;"    "  adcx %%rax, %%r12;"    /* f[2]*f[3] */
+		"  mulxq 40(%1), %%r11, %%rbx;"     "  adcx %%rcx, %%r11;"    /* f[1]*f[3] */
+		"  mulxq 48(%1), %%rax, %%r13;"    "  adcx %%rax, %%rbx;"    /* f[2]*f[3] */
 		"  movq 40(%1), %%rdx;"             "  adcx %%r15, %%r13;"    /* f1 */
 		"  mulxq 48(%1), %%rax, %%rcx;"    "  mov $0, %%r14;"        /* f[2]*f[1] */
 
@@ -651,12 +651,12 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
 		"  adcx %%r8, %%r8;"
 		"  adox %%rcx, %%r11;"
 		"  adcx %%r9, %%r9;"
-		"  adox %%r15, %%r12;"
+		"  adox %%r15, %%rbx;"
 		"  adcx %%r10, %%r10;"
 		"  adox %%r15, %%r13;"
 		"  adcx %%r11, %%r11;"
 		"  adox %%r15, %%r14;"
-		"  adcx %%r12, %%r12;"
+		"  adcx %%rbx, %%rbx;"
 		"  adcx %%r13, %%r13;"
 		"  adcx %%r14, %%r14;"
 
@@ -669,7 +669,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
 		"  adcx %%rcx, %%r10;"     "  movq %%r10, 88(%0);"
 		"  movq 48(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[2]^2 */
 		"  adcx %%rax, %%r11;"     "  movq %%r11, 96(%0);"
-		"  adcx %%rcx, %%r12;"     "  movq %%r12, 104(%0);"
+		"  adcx %%rcx, %%rbx;"     "  movq %%rbx, 104(%0);"
 		"  movq 56(%1), %%rdx;"    "  mulx %%rdx, %%rax, %%rcx;"    /* f[3]^2 */
 		"  adcx %%rax, %%r13;"     "  movq %%r13, 112(%0);"
 		"  adcx %%rcx, %%r14;"     "  movq %%r14, 120(%0);"
@@ -683,11 +683,11 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
 		"  mulxq 32(%1), %%r8, %%r13;"
 		"  xor %%rcx, %%rcx;"
 		"  adoxq 0(%1), %%r8;"
-		"  mulxq 40(%1), %%r9, %%r12;"
+		"  mulxq 40(%1), %%r9, %%rbx;"
 		"  adcx %%r13, %%r9;"
 		"  adoxq 8(%1), %%r9;"
 		"  mulxq 48(%1), %%r10, %%r13;"
-		"  adcx %%r12, %%r10;"
+		"  adcx %%rbx, %%r10;"
 		"  adoxq 16(%1), %%r10;"
 		"  mulxq 56(%1), %%r11, %%rax;"
 		"  adcx %%r13, %%r11;"
@@ -716,11 +716,11 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
 		"  mulxq 96(%1), %%r8, %%r13;"
 		"  xor %%rcx, %%rcx;"
 		"  adoxq 64(%1), %%r8;"
-		"  mulxq 104(%1), %%r9, %%r12;"
+		"  mulxq 104(%1), %%r9, %%rbx;"
 		"  adcx %%r13, %%r9;"
 		"  adoxq 72(%1), %%r9;"
 		"  mulxq 112(%1), %%r10, %%r13;"
-		"  adcx %%r12, %%r10;"
+		"  adcx %%rbx, %%r10;"
 		"  adoxq 80(%1), %%r10;"
 		"  mulxq 120(%1), %%r11, %%rax;"
 		"  adcx %%r13, %%r11;"
@@ -745,7 +745,7 @@ static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
 		"  movq %%r8, 32(%0);"
 	: "+&r" (tmp), "+&r" (f), "+&r" (out)
 	:
-	: "%rax", "%rcx", "%rdx", "%r8", "%r9", "%r10", "%r11", "%r12", "%r13", "%r14", "%r15", "memory", "cc"
+	: "%rax", "%rcx", "%rdx", "%r8", "%r9", "%r10", "%r11", "%rbx", "%r13", "%r14", "%r15", "memory", "cc"
 	);
 }