567eefcaf
Denys Vlasenko
2021-10-06
Subject
tls: P256: do not dumplicate sp_256_sub_8()
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networking/tls_sp_c32.c+3 -23
| @@ -291,10 +291,10 @@ static int sp_256_sub_8(sp_digit* r, const sp_digit* a, const sp_digit* b) | |
| #endif | |
| } | |
| + | #if ALLOW_ASM && defined(__GNUC__) && defined(__i386__) |
| /* Sub p256_mod from a into r. (r = a - p256_mod). */ | |
| static void sp_256_sub_8_p256_mod(sp_digit* r, const sp_digit* a) | |
| { | |
| - | #if ALLOW_ASM && defined(__GNUC__) && defined(__i386__) |
| sp_digit reg; | |
| //p256_mod[7..0] = ffffffff 00000001 00000000 00000000 00000000 ffffffff ffffffff ffffffff | |
| asm volatile ( | |
| @@ -334,30 +334,10 @@ static void sp_256_sub_8_p256_mod(sp_digit* r, const sp_digit* a) | |
| : "0" (a), "1" (r) | |
| : "memory" | |
| ); | |
| + | } |
| #else | |
| - | const sp_digit* b = p256_mod; |
| - | int i; |
| - | sp_digit borrow; |
| - | |
| - | borrow = 0; |
| - | for (i = 0; i < 8; i++) { |
| - | sp_digit w, v; |
| - | w = b[i] + borrow; |
| - | v = a[i]; |
| - | if (w != 0) { |
| - | v = a[i] - w; |
| - | borrow = (v > a[i]); |
| - | /* hope compiler detects above as "carry flag set" */ |
| - | } |
| - | /* else: b + borrow == 0, two cases: |
| - | * b:ffffffff, borrow:1 |
| - | * b:00000000, borrow:0 |
| - | * in either case, r[i] = a[i] and borrow remains unchanged |
| - | */ |
| - | r[i] = v; |
| - | } |
| + | # define sp_256_sub_8_p256_mod(r, a) sp_256_sub_8((r), (a), p256_mod) |
| #endif | |
| - | } |
| /* Multiply a and b into r. (r = a * b) */ | |
| static void sp_256_mul_8(sp_digit* r, const sp_digit* a, const sp_digit* b) | |