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Use GCC extended assembler

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Naked functions and basic assembler don't seem to work reliably - basic
assembler is assumed to not change registers or memory, and there does
not appear to be any special handling of naked functions in this regard.

Signed-off-by: Kevin Bracey <kevin.bracey@arm.com>
This commit is contained in:
Kevin Bracey 2020-10-02 14:44:40 +03:00
parent e0f88d5140
commit 0a1884bba4
1 changed files with 12 additions and 13 deletions
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25
tinycrypt/ecc.c
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@ -598,18 +598,15 @@ static __asm void muladd(uECC_word_t a, uECC_word_t b, uECC_word_t r[3])
BX lr
#endif
}
#elif defined MBEDTLS_HAVE_ASM && (defined __GNUC__ || defined __clang__) && defined __arm__
static __attribute__((__naked__))
void muladd(uECC_word_t a, uECC_word_t b, uECC_word_t r[3])
#elif defined MBEDTLS_HAVE_ASM && defined __GNUC__ && defined __arm__
static void muladd(uECC_word_t a, uECC_word_t b, uECC_word_t r[3])
{
asm(
register uECC_word_t r0 asm ("r0") = a;
register uECC_word_t r1 asm ("r1") = b;
register uECC_word_t *r2 asm ("r2") = r;
asm volatile (
#if defined __thumb__ && !defined(__thumb2__)
".syntax unified \n\t"
"PUSH {r4-r5} \n\t"
".cfi_remember_state \n\t"
".cfi_adjust_cfa_offset 8 \n\t"
".cfi_rel_offset r4,0 \n\t"
".cfi_rel_offset r5,4 \n\t"
// __ARM_common_mul_uu replacement - inline, faster, don't touch R2
// Separate operands into halfwords
"UXTH r3,r0 \n\t" // r3 := a.lo
@ -640,9 +637,9 @@ void muladd(uECC_word_t a, uECC_word_t b, uECC_word_t r[3])
"ADCS r5,r0 \n\t"
"SUBS r2,#12 \n\t"
"STMIA r2!,{r3,r4,r5} \n\t"
"POP {r4-r5} \n\t"
".cfi_restore_state \n\t"
"BX lr \n\t"
: "+r" (r0), "+r" (r1), "+r" (r2)
:
: "r3", "r4", "r5", "ip", "cc", "memory"
#else
"UMULL r3,ip,r0,r1 \n\t" // pre-ARMv6 requires Rd[Lo|Hi] != Rn
"LDMIA r2,{r0,r1} \n\t"
@ -651,7 +648,9 @@ void muladd(uECC_word_t a, uECC_word_t b, uECC_word_t r[3])
"ADCS r1,r1,ip \n\t"
"ADC r3,r3,#0 \n\t"
"STMIA r2!,{r0,r1,r3} \n\t"
"BX lr \n\t"
: "+r" (r0), "+r" (r1), "+r" (r2)
:
: "r3", "ip", "cc", "memory"
#endif
);
}