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[crypto] Add memory output constraints for big-integer inline assembly

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The ARM versions of the big-integer inline assembly functions include
constraints to indicate that the output value is modified by the
assembly code.  These constraints are not present in the equivalent
code for the x86 versions.

As of GCC 11, this results in the compiler reporting that the output
values may be uninitialized.

Fix by including the relevant memory output constraints.

Reported-by: Christian Hesse <mail@eworm.de>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2021-06-03 13:34:14 +01:00
parent 74c54461cb
commit f3f568e382
2 changed files with 43 additions and 22 deletions
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11
src/arch/x86/core/x86_bigint.c
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@@ -75,17 +75,18 @@ void bigint_multiply_raw ( const uint32_t *multiplicand0,
*
* a < 2^{n}, b < 2^{n} => ab < 2^{2n}
*/
__asm__ __volatile__ ( "mull %4\n\t"
"addl %%eax, (%5,%2,4)\n\t"
"adcl %%edx, 4(%5,%2,4)\n\t"
__asm__ __volatile__ ( "mull %5\n\t"
"addl %%eax, (%6,%2,4)\n\t"
"adcl %%edx, 4(%6,%2,4)\n\t"
"\n1:\n\t"
"adcl $0, 8(%5,%2,4)\n\t"
"adcl $0, 8(%6,%2,4)\n\t"
"inc %2\n\t"
/* Does not affect CF */
"jc 1b\n\t"
: "=&a" ( discard_a ),
"=&d" ( discard_d ),
"=&r" ( index )
"=&r" ( index ),
"+m" ( *result )
: "0" ( multiplicand_element ),
"g" ( multiplier_element ),
"r" ( result_elements ),