On Thu, Jan 12, 2017 at 08:37:18PM -0800, Linus Torvalds wrote: > > So then the compiler actually needs to start adding useless instructions > just to keep the stack 16-byte aligned.
Which it does. Of course most of the time no extra instructions are required because there are stack variables, so it's just matter of adding 8 to the value you're subtracting from rsp. But it is probably why gcc assumes that the stack is 16-byte aligned which triggered my original crash. Here is an example from the function that was involved in the crash, without frame pointers: 00000000000001b0 <chacha20_simd>: 1b0: 41 54 push %r12 1b2: 55 push %rbp 1b3: 48 81 ec f8 00 00 00 sub $0xf8,%rsp Cheers, -- Email: Herbert Xu <herb...@gondor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
