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Add aarch32 const-time asm

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman
2023-05-13 12:48:02 +01:00
committed by Dave Rodgman
parent c9ed5dee69
commit ef2527901e
1 changed files with 44 additions and 0 deletions
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44
library/constant_time_impl.h
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@ -132,6 +132,18 @@ static inline mbedtls_ct_condition_t mbedtls_ct_bool(mbedtls_ct_uint_t x)
:
);
return (mbedtls_ct_condition_t) x;
#elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32)
uint32_t s;
asm volatile ("neg %[s], %[x] \n\t"
"orr %[x], %[x], %[s] \n\t"
"asr %[x], %[x], #31"
:
[s] "=&l" (s),
[x] "+&l" (x)
:
:
);
return (mbedtls_ct_condition_t) x;
#else
const mbedtls_ct_uint_t xo = mbedtls_ct_compiler_opaque(x);
#if defined(_MSC_VER)
@ -165,6 +177,19 @@ static inline mbedtls_ct_uint_t mbedtls_ct_if(mbedtls_ct_condition_t condition,
:
);
return (mbedtls_ct_uint_t) condition;
#elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32)
asm volatile ("and %[if1], %[if1], %[condition] \n\t"
"mvn %[condition], %[condition] \n\t"
"and %[condition], %[condition], %[if0] \n\t"
"orr %[condition], %[if1], %[condition]"
:
[condition] "+&l" (condition),
[if1] "+&l" (if1)
:
[if0] "l" (if0)
:
);
return (mbedtls_ct_uint_t) condition;
#else
mbedtls_ct_condition_t not_cond =
(mbedtls_ct_condition_t) (~mbedtls_ct_compiler_opaque(condition));
@ -187,6 +212,25 @@ static inline mbedtls_ct_condition_t mbedtls_ct_uint_lt(mbedtls_ct_uint_t x, mbe
:
);
return (mbedtls_ct_condition_t) x;
#elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32)
uint32_t s1;
asm volatile (
#if defined(__thumb__) && !defined(__thumb2__)
"mov %[s1], %[x] \n\t"
"eor %[s1], %[s1], %[y] \n\t"
#else
"eor %[s1], %[x], %[y] \n\t"
#endif
"sub %[x], %[x], %[y] \n\t"
"bic %[x], %[x], %[s1] \n\t"
"and %[y], %[s1], %[y] \n\t"
"orr %[x], %[x], %[y] \n\t"
"asr %[x], %[x], #31"
: [s1] "=&l" (s1), [x] "+&l" (x), [y] "+&l" (y)
:
:
);
return (mbedtls_ct_condition_t) x;
#else
/* Ensure that the compiler cannot optimise the following operations over x and y,
* even if it knows the value of x and y.