diff options
| author | Michael Brown <mcb30@ipxe.org> | 2024-11-26 12:53:01 +0000 |
|---|---|---|
| committer | Michael Brown <mcb30@ipxe.org> | 2024-11-26 12:55:13 +0000 |
| commit | 167a08f08928c7e469f50d5d364287abb784e99c (patch) | |
| tree | 039a60c76e5da50dfe17cffb41c4491087c2c74f /src/arch/riscv/include/bits/bigint.h | |
| parent | da6da6eb3b83fe92002e9c8e245933498ba19a48 (diff) | |
| download | ipxe-167a08f08928c7e469f50d5d364287abb784e99c.tar.gz | |
[crypto] Expose carry flag from big integer addition and subtraction
Expose the effective carry (or borrow) out flag from big integer
addition and subtraction, and use this to elide an explicit bit test
when performing x25519 reduction.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Diffstat (limited to 'src/arch/riscv/include/bits/bigint.h')
| -rw-r--r-- | src/arch/riscv/include/bits/bigint.h | 36 |
1 files changed, 20 insertions, 16 deletions
diff --git a/src/arch/riscv/include/bits/bigint.h b/src/arch/riscv/include/bits/bigint.h index 5b22b9ac7..ab1070d88 100644 --- a/src/arch/riscv/include/bits/bigint.h +++ b/src/arch/riscv/include/bits/bigint.h @@ -43,8 +43,9 @@ bigint_init_raw ( unsigned long *value0, unsigned int size, * @v addend0 Element 0 of big integer to add * @v value0 Element 0 of big integer to be added to * @v size Number of elements + * @ret carry Carry out */ -static inline __attribute__ (( always_inline )) void +static inline __attribute__ (( always_inline )) int bigint_add_raw ( const unsigned long *addend0, unsigned long *value0, unsigned int size ) { bigint_t ( size ) __attribute__ (( may_alias )) *value = @@ -54,19 +55,19 @@ bigint_add_raw ( const unsigned long *addend0, unsigned long *value0, unsigned long *discard_value; unsigned long discard_addend_i; unsigned long discard_value_i; - unsigned long discard_carry; unsigned long discard_temp; + unsigned long carry; __asm__ __volatile__ ( "\n1:\n\t" /* Load addend[i] and value[i] */ LOADN " %2, (%0)\n\t" LOADN " %3, (%1)\n\t" /* Add carry flag and addend */ - "add %3, %3, %4\n\t" - "sltu %5, %3, %4\n\t" + "add %3, %3, %5\n\t" + "sltu %4, %3, %5\n\t" "add %3, %3, %2\n\t" - "sltu %4, %3, %2\n\t" - "or %4, %4, %5\n\t" + "sltu %5, %3, %2\n\t" + "or %5, %4, %5\n\t" /* Store value[i] */ STOREN " %3, (%1)\n\t" /* Loop */ @@ -77,12 +78,13 @@ bigint_add_raw ( const unsigned long *addend0, unsigned long *value0, "=&r" ( discard_value ), "=&r" ( discard_addend_i ), "=&r" ( discard_value_i ), - "=&r" ( discard_carry ), "=&r" ( discard_temp ), + "=&r" ( carry ), "+m" ( *value ) : "r" ( valueN ), "i" ( sizeof ( unsigned long ) ), - "0" ( addend0 ), "1" ( value0 ), "4" ( 0 ) ); + "0" ( addend0 ), "1" ( value0 ), "5" ( 0 ) ); + return carry; } /** @@ -91,8 +93,9 @@ bigint_add_raw ( const unsigned long *addend0, unsigned long *value0, * @v subtrahend0 Element 0 of big integer to subtract * @v value0 Element 0 of big integer to be subtracted from * @v size Number of elements + * @ret borrow Borrow out */ -static inline __attribute__ (( always_inline )) void +static inline __attribute__ (( always_inline )) int bigint_subtract_raw ( const unsigned long *subtrahend0, unsigned long *value0, unsigned int size ) { bigint_t ( size ) __attribute__ (( may_alias )) *value = @@ -102,19 +105,19 @@ bigint_subtract_raw ( const unsigned long *subtrahend0, unsigned long *value0, unsigned long *discard_value; unsigned long discard_subtrahend_i; unsigned long discard_value_i; - unsigned long discard_carry; unsigned long discard_temp; + unsigned long borrow; __asm__ __volatile__ ( "\n1:\n\t" /* Load subtrahend[i] and value[i] */ LOADN " %2, (%0)\n\t" LOADN " %3, (%1)\n\t" /* Subtract carry flag and subtrahend */ - "sltu %5, %3, %4\n\t" - "sub %3, %3, %4\n\t" - "sltu %4, %3, %2\n\t" + "sltu %4, %3, %5\n\t" + "sub %3, %3, %5\n\t" + "sltu %5, %3, %2\n\t" "sub %3, %3, %2\n\t" - "or %4, %4, %5\n\t" + "or %5, %5, %4\n\t" /* Store value[i] */ STOREN " %3, (%1)\n\t" /* Loop */ @@ -125,13 +128,14 @@ bigint_subtract_raw ( const unsigned long *subtrahend0, unsigned long *value0, "=&r" ( discard_value ), "=&r" ( discard_subtrahend_i ), "=&r" ( discard_value_i ), - "=&r" ( discard_carry ), "=&r" ( discard_temp ), + "=&r" ( borrow ), "+m" ( *value ) : "r" ( valueN ), "i" ( sizeof ( unsigned long ) ), "0" ( subtrahend0 ), "1" ( value0 ), - "4" ( 0 ) ); + "5" ( 0 ) ); + return borrow; } /** |