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5e9c61702

Denys Vlasenko
Denys Vlasenko
2021-10-06
SUCCESS Duration: 155s

Subject

tls: P256: sp_256_sub_8_p256_mod always subtracts in-place, use that

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Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

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Commit Diff GitHub →

networking/tls_sp_c32.c +36 -63
networking/tls_sp_c32.c+36 -63
@@ -346,82 +346,55 @@ static int sp_256_sub_8(sp_digit* r, const sp_digit* a, const sp_digit* b)
#endif
}
-/* Sub p256_mod from a into r. (r = a - p256_mod). */
+/* Sub p256_mod from r. (r = r - p256_mod). */
#if ALLOW_ASM && defined(__GNUC__) && defined(__i386__)
-static void sp_256_sub_8_p256_mod(sp_digit* r, const sp_digit* a)
+static void sp_256_sub_8_p256_mod(sp_digit* r)
{
- sp_digit reg;
//p256_mod[7..0] = ffffffff 00000001 00000000 00000000 00000000 ffffffff ffffffff ffffffff
asm volatile (
-"\n movl (%0), %2"
-"\n subl $0xffffffff, %2"
-"\n movl %2, (%1)"
-"\n"
-"\n movl 1*4(%0), %2"
-"\n sbbl $0xffffffff, %2"
-"\n movl %2, 1*4(%1)"
-"\n"
-"\n movl 2*4(%0), %2"
-"\n sbbl $0xffffffff, %2"
-"\n movl %2, 2*4(%1)"
-"\n"
-"\n movl 3*4(%0), %2"
-"\n sbbl $0, %2"
-"\n movl %2, 3*4(%1)"
-"\n"
-"\n movl 4*4(%0), %2"
-"\n sbbl $0, %2"
-"\n movl %2, 4*4(%1)"
+"\n subl $0xffffffff, (%0)"
+"\n sbbl $0xffffffff, 1*4(%0)"
+"\n sbbl $0xffffffff, 2*4(%0)"
+"\n sbbl $0, 3*4(%0)"
+"\n sbbl $0, 4*4(%0)"
+"\n sbbl $0, 5*4(%0)"
+"\n sbbl $1, 6*4(%0)"
+"\n sbbl $0xffffffff, 7*4(%0)"
"\n"
-"\n movl 5*4(%0), %2"
-"\n sbbl $0, %2"
-"\n movl %2, 5*4(%1)"
-"\n"
-"\n movl 6*4(%0), %2"
-"\n sbbl $1, %2"
-"\n movl %2, 6*4(%1)"
-"\n"
-"\n movl 7*4(%0), %2"
-"\n sbbl $0xffffffff, %2"
-"\n movl %2, 7*4(%1)"
-"\n"
- : "=r" (a), "=r" (r), "=r" (reg)
- : "0" (a), "1" (r)
+ : "=r" (r)
+ : "0" (r)
: "memory"
);
}
#elif ALLOW_ASM && defined(__GNUC__) && defined(__x86_64__)
-static void sp_256_sub_8_p256_mod(sp_digit* r, const sp_digit* a)
+static void sp_256_sub_8_p256_mod(sp_digit* r)
{
uint64_t reg;
uint64_t ooff;
//p256_mod[3..0] = ffffffff00000001 0000000000000000 00000000ffffffff ffffffffffffffff
asm volatile (
-"\n movq (%0), %3"
-"\n addq $1, %3" // adding 1 is the same as subtracting ffffffffffffffff
-"\n movq %3, (%1)" //
+"\n addq $1, (%0)" // adding 1 is the same as subtracting ffffffffffffffff
"\n cmc" // only carry bit needs inverting
+
+"\n sbbq %1, 1*8(%0)" // %1 holds 00000000ffffffff
+
+"\n sbbq $0, 2*8(%0)"
"\n"
-"\n movq 1*8(%0), %3"
-"\n sbbq %2, %3" // %2 holds 00000000ffffffff
-"\n movq %3, 1*8(%1)"
-"\n"
-"\n movq 2*8(%0), %3"
-"\n sbbq $0, %3"
-"\n movq %3, 2*8(%1)"
-"\n"
-"\n movq 3*8(%0), %3"
-"\n sbbq $0, %3" // adding 00000000ffffffff (in %2)
-"\n addq %2, %3" // is the same as subtracting ffffffff00000001
-"\n movq %3, 3*8(%1)"
+"\n movq 3*8(%0), %2"
+"\n sbbq $0, %2" // adding 00000000ffffffff (in %1)
+"\n addq %1, %2" // is the same as subtracting ffffffff00000001
+"\n movq %2, 3*8(%0)"
"\n"
- : "=r" (a), "=r" (r), "=r" (ooff), "=r" (reg)
- : "0" (a), "1" (r), "2" (0x00000000ffffffff)
+ : "=r" (r), "=r" (ooff), "=r" (reg)
+ : "0" (r), "1" (0x00000000ffffffff)
: "memory"
);
}
#else
-# define sp_256_sub_8_p256_mod(r, a) sp_256_sub_8((r), (a), p256_mod)
+static void sp_256_sub_8_p256_mod(sp_digit* r)
+{
+ sp_256_sub_8(r, r, p256_mod);
+}
#endif
/* Multiply a and b into r. (r = a * b) */
@@ -609,7 +582,7 @@ static void sp_256_mont_add_8(sp_digit* r, const sp_digit* a, const sp_digit* b
int carry = sp_256_add_8(r, a, b);
sp_256_norm_8(r);
if (carry) {
- sp_256_sub_8_p256_mod(r, r /*, m*/);
+ sp_256_sub_8_p256_mod(r);
sp_256_norm_8(r);
}
}
@@ -637,7 +610,7 @@ static void sp_256_mont_dbl_8(sp_digit* r, const sp_digit* a /*, const sp_digit*
int carry = sp_256_add_8(r, a, a);
sp_256_norm_8(r);
if (carry)
- sp_256_sub_8_p256_mod(r, r /*, m*/);
+ sp_256_sub_8_p256_mod(r);
sp_256_norm_8(r);
}
@@ -649,13 +622,13 @@ static void sp_256_mont_tpl_8(sp_digit* r, const sp_digit* a /*, const sp_digit*
int carry = sp_256_add_8(r, a, a);
sp_256_norm_8(r);
if (carry) {
- sp_256_sub_8_p256_mod(r, r /*, m*/);
+ sp_256_sub_8_p256_mod(r);
sp_256_norm_8(r);
}
carry = sp_256_add_8(r, r, a);
sp_256_norm_8(r);
if (carry) {
- sp_256_sub_8_p256_mod(r, r /*, m*/);
+ sp_256_sub_8_p256_mod(r);
sp_256_norm_8(r);
}
}
@@ -829,7 +802,7 @@ static void sp_256_mont_reduce_8(sp_digit* a/*, const sp_digit* m, sp_digit mp*/
}
sp_256_mont_shift_8(a, a);
if (word16th != 0)
- sp_256_sub_8_p256_mod(a, a /*, m*/);
+ sp_256_sub_8_p256_mod(a);
sp_256_norm_8(a);
}
else { /* Same code for explicit mp == 1 (which is always the case for P256) */
@@ -849,7 +822,7 @@ static void sp_256_mont_reduce_8(sp_digit* a/*, const sp_digit* m, sp_digit mp*/
}
sp_256_mont_shift_8(a, a);
if (word16th != 0)
- sp_256_sub_8_p256_mod(a, a /*, m*/);
+ sp_256_sub_8_p256_mod(a);
sp_256_norm_8(a);
}
}
@@ -1104,7 +1077,7 @@ static void sp_256_map_8(sp_point* r, sp_point* p)
sp_256_mont_reduce_8(r->x /*, p256_mod, p256_mp_mod*/);
/* Reduce x to less than modulus */
if (sp_256_cmp_8(r->x, p256_mod) >= 0)
- sp_256_sub_8_p256_mod(r->x, r->x /*, p256_mod*/);
+ sp_256_sub_8_p256_mod(r->x);
sp_256_norm_8(r->x);
/* y /= z^3 */
@@ -1113,7 +1086,7 @@ static void sp_256_map_8(sp_point* r, sp_point* p)
sp_256_mont_reduce_8(r->y /*, p256_mod, p256_mp_mod*/);
/* Reduce y to less than modulus */
if (sp_256_cmp_8(r->y, p256_mod) >= 0)
- sp_256_sub_8_p256_mod(r->y, r->y /*, p256_mod*/);
+ sp_256_sub_8_p256_mod(r->y);
sp_256_norm_8(r->y);
memset(r->z, 0, sizeof(r->z));