From 7c847235e8f0e0b877c505f19733b417bb65ff2e Mon Sep 17 00:00:00 2001 From: Gilles Peskine Date: Tue, 14 Sep 2021 00:13:05 +0200 Subject: [PATCH] x86_64 MULADDC assembly: add missing constraints about memory MULADDC_CORE reads from (%%rsi) and writes to (%%rdi). This fragment is repeated up to 16 times, and %%rsi and %%rdi are s and d on entry respectively. Hence the complete asm statement reads 16 64-bit words from memory starting at s, and writes 16 64-bit words starting at d. Without any declaration of modified memory, Clang 12 and Clang 13 generated non-working code for mbedtls_mpi_mod_exp. The constraints make the unit tests pass with Clang 12. Signed-off-by: Gilles Peskine --- include/mbedtls/bn_mul.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/mbedtls/bn_mul.h b/include/mbedtls/bn_mul.h index 6f1201bf50a..f84f9650ddc 100644 --- a/include/mbedtls/bn_mul.h +++ b/include/mbedtls/bn_mul.h @@ -256,9 +256,9 @@ "addq $8, %%rdi\n" #define MULADDC_STOP \ - : "+c" (c), "+D" (d), "+S" (s) \ - : "b" (b) \ - : "rax", "rdx", "r8" \ + : "+c" (c), "+D" (d), "+S" (s), "+m" (*(uint64_t (*)[16]) d) \ + : "b" (b), "m" (*(const uint64_t (*)[16]) s) \ + : "rax", "rdx", "r8" \ ); #endif /* AMD64 */