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Fix unified asm syntax issue

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2023-06-12 15:38:49 +01:00 • committed by Dave Rodgman
parent ef2527901e
commit 822c9c7d4e
1 changed files with 46 additions and 15 deletions
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61
library/constant_time_impl.h
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@ -134,14 +134,39 @@ static inline mbedtls_ct_condition_t mbedtls_ct_bool(mbedtls_ct_uint_t x)
return (mbedtls_ct_condition_t) x; return (mbedtls_ct_condition_t) x;
#elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32) #elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32)
uint32_t s; uint32_t s;
asm volatile ("neg %[s], %[x] \n\t" /*
"orr %[x], %[x], %[s] \n\t" * Selecting unified syntax is needed for gcc, and harmless on clang.
"asr %[x], %[x], #31" *
* This is needed because on Thumb 1, condition flags are always set, so
* e.g. "negs" is supported but "neg" is not (on Thumb 2, both exist).
*
* Under Thumb 1 unified syntax, only the "negs" form is accepted, and
* under divided syntax, only the "neg" form is accepted. clang only
* supports unified syntax.
*
* On Thumb 2 and Arm, both compilers are happy with the "s" suffix,
* although we don't actually care about setting the flags.
*
* For gcc, restore divided syntax afterwards - otherwise old versions of gcc
* seem to apply unified syntax globally, which breaks other asm code.
*/
#if !defined(__clang__)
#define RESTORE_ASM_SYNTAX ".syntax divided \n\t"
#else
#define RESTORE_ASM_SYNTAX
#endif
asm volatile (".syntax unified \n\t"
"negs %[s], %[x] \n\t"
"orrs %[x], %[x], %[s] \n\t"
"asrs %[x], %[x], #31 \n\t"
RESTORE_ASM_SYNTAX
: :
[s] "=&l" (s), [s] "=&l" (s),
[x] "+&l" (x) [x] "+&l" (x)
: :
: :
"cc" /* clobbers flag bits */
); );
return (mbedtls_ct_condition_t) x; return (mbedtls_ct_condition_t) x;
#else #else
@ -178,16 +203,19 @@ static inline mbedtls_ct_uint_t mbedtls_ct_if(mbedtls_ct_condition_t condition,
); );
return (mbedtls_ct_uint_t) condition; return (mbedtls_ct_uint_t) condition;
#elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32) #elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32)
asm volatile ("and %[if1], %[if1], %[condition] \n\t" asm volatile (".syntax unified \n\t"
"mvn %[condition], %[condition] \n\t" "ands %[if1], %[if1], %[condition] \n\t"
"and %[condition], %[condition], %[if0] \n\t" "mvns %[condition], %[condition] \n\t"
"orr %[condition], %[if1], %[condition]" "ands %[condition], %[condition], %[if0] \n\t"
"orrs %[condition], %[if1], %[condition] \n\t"
RESTORE_ASM_SYNTAX
: :
[condition] "+&l" (condition), [condition] "+&l" (condition),
[if1] "+&l" (if1) [if1] "+&l" (if1)
: :
[if0] "l" (if0) [if0] "l" (if0)
: :
"cc"
); );
return (mbedtls_ct_uint_t) condition; return (mbedtls_ct_uint_t) condition;
#else #else
@ -215,20 +243,23 @@ static inline mbedtls_ct_condition_t mbedtls_ct_uint_lt(mbedtls_ct_uint_t x, mbe
#elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32) #elif defined(MBEDTLS_CT_ARM_ASM) && defined(MBEDTLS_CT_SIZE_32)
uint32_t s1; uint32_t s1;
asm volatile ( asm volatile (
".syntax unified \n\t"
#if defined(__thumb__) && !defined(__thumb2__) #if defined(__thumb__) && !defined(__thumb2__)
"mov %[s1], %[x] \n\t" "movs %[s1], %[x] \n\t"
"eor %[s1], %[s1], %[y] \n\t" "eors %[s1], %[s1], %[y] \n\t"
#else #else
"eor %[s1], %[x], %[y] \n\t" "eors %[s1], %[x], %[y] \n\t"
#endif #endif
"sub %[x], %[x], %[y] \n\t" "subs %[x], %[x], %[y] \n\t"
"bic %[x], %[x], %[s1] \n\t" "bics %[x], %[x], %[s1] \n\t"
"and %[y], %[s1], %[y] \n\t" "ands %[y], %[s1], %[y] \n\t"
"orr %[x], %[x], %[y] \n\t" "orrs %[x], %[x], %[y] \n\t"
"asr %[x], %[x], #31" "asrs %[x], %[x], #31 \n\t"
RESTORE_ASM_SYNTAX
: [s1] "=&l" (s1), [x] "+&l" (x), [y] "+&l" (y) : [s1] "=&l" (s1), [x] "+&l" (x), [y] "+&l" (y)
: :
: :
"cc"
); );
return (mbedtls_ct_condition_t) x; return (mbedtls_ct_condition_t) x;
#else #else