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| 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/arm32/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/arm32/include/bits/bigint.h')
| -rw-r--r-- | src/arch/arm32/include/bits/bigint.h | 23 |
1 files changed, 15 insertions, 8 deletions
diff --git a/src/arch/arm32/include/bits/bigint.h b/src/arch/arm32/include/bits/bigint.h index 39d3dc347..95de32d83 100644 --- a/src/arch/arm32/include/bits/bigint.h +++ b/src/arch/arm32/include/bits/bigint.h @@ -43,8 +43,9 @@ bigint_init_raw ( uint32_t *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 uint32_t *addend0, uint32_t *value0, unsigned int size ) { bigint_t ( size ) __attribute__ (( may_alias )) *value = @@ -54,8 +55,9 @@ bigint_add_raw ( const uint32_t *addend0, uint32_t *value0, uint32_t *discard_end; uint32_t discard_addend_i; uint32_t discard_value_i; + int carry; - __asm__ __volatile__ ( "adds %2, %0, %8, lsl #2\n\t" /* clear CF */ + __asm__ __volatile__ ( "adds %2, %0, %9, lsl #2\n\t" /* clear CF */ "\n1:\n\t" "ldmia %0!, {%3}\n\t" "ldr %4, [%1]\n\t" @@ -68,9 +70,11 @@ bigint_add_raw ( const uint32_t *addend0, uint32_t *value0, "=l" ( discard_end ), "=l" ( discard_addend_i ), "=l" ( discard_value_i ), + "=@cccs" ( carry ), "+m" ( *value ) - : "0" ( addend0 ), "1" ( value0 ), "l" ( size ) - : "cc" ); + : "0" ( addend0 ), "1" ( value0 ), + "l" ( size ) ); + return carry; } /** @@ -79,8 +83,9 @@ bigint_add_raw ( const uint32_t *addend0, uint32_t *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 uint32_t *subtrahend0, uint32_t *value0, unsigned int size ) { bigint_t ( size ) __attribute__ (( may_alias )) *value = @@ -90,8 +95,9 @@ bigint_subtract_raw ( const uint32_t *subtrahend0, uint32_t *value0, uint32_t *discard_end; uint32_t discard_subtrahend_i; uint32_t discard_value_i; + int borrow; - __asm__ __volatile__ ( "add %2, %0, %8, lsl #2\n\t" + __asm__ __volatile__ ( "add %2, %0, %9, lsl #2\n\t" "cmp %2, %0\n\t" /* set CF */ "\n1:\n\t" "ldmia %0!, {%3}\n\t" @@ -105,10 +111,11 @@ bigint_subtract_raw ( const uint32_t *subtrahend0, uint32_t *value0, "=l" ( discard_end ), "=l" ( discard_subtrahend_i ), "=l" ( discard_value_i ), + "=@cccc" ( borrow ), "+m" ( *value ) : "0" ( subtrahend0 ), "1" ( value0 ), - "l" ( size ) - : "cc" ); + "l" ( size ) ); + return borrow; } /** |