Reputation: 13
I have a segfault when I try to load in some ciphertext I have generated using intrinsics. I do not understand the error at all. Code sample:
unsigned char c[177];
unsigned char m[161];
auth = _mm_setzero_si128();
unsigned char M_star[BLOCKSIZE];
__m128i tag = auth;
for(i=0;i<numblocks_mes;++i)
{
M = _mm_load_si128(m+i*BLOCKSIZE);
idx = _mm_set_epi64x(zero,i); // both inputs are unsigned long long
tmp = encrypt_block(M,idx);
tag = _mm_xor_si128(tag,tmp);
}
if(fin_mes)
{
memcpy(M_star,m+numblocks_mes*BLOCKSIZE,fin_mes);
A_star[fin_mes] = 0x80;
memset(M_star+fin_mes+1,0,BLOCKSIZE-(fin_mes+1));
M = _mm_load_si128(M_star);
idx = _mm_set_epi64x(tag_fin,numblocks_mes); // both inputs are unsigned long long
tmp = encrypt_block(M,idx); // Contains calls to AES
tag = _mm_xor_si128(tag,tmp);
}
// print128_asint(tag);
tag = encrypt_block(tag,nonce);
// Following line causes segfault
_mm_store_si128( (__m128i *)&c[numblocks_mes*BLOCKSIZE+fin_mes], tag ); // numblocks_mes*BLOCKSIZE+fin_mes = 161
I have tried looking through other similar questions before, and tried them out, but I haven't found anything that worked for me.
Upvotes: 1
Views: 520
Reputation: 213180
The destination address needs to be 16 byte aligned. Since c[]
itself has no particular alignment then there are no guarantees about addresses at arbitrary offsets within c
either (even if those offsets are multiples of 16).
Solution: use _mm_storeu_si128
instead of _mm_store_si128
.
m
and Mstar
- you should almost certainly change these to use _mm_loadu_si128
.
Upvotes: 2