Re: [PATCH v2 3/4] secure_seq: use siphash24 instead of md5_transform

Jason A. Donenfeld
2016-12-14T19:38:43Z

Hi Hannes,

On Wed, Dec 14, 2016 at 8:22 PM, Hannes Frederic Sowa
<hannes@stressinduktion.org> wrote:
> I don't think this helps. Did you test it? I don't see reason why
> padding could be left out between `d' and `end' because of the flexible
> array member?

Because the type u8 doesn't require any alignment requirements, it can
nestle right up there cozy with the u16:

zx2c4@thinkpad ~ $ cat a.c
#include <stdint.h>
#include <stdio.h>
#include <stddef.h>
int main()
{
struct {
uint64_t a;
uint32_t b;
uint32_t c;
uint16_t d;
char x[];
} a;
printf("%zu\n", sizeof(a));
printf("%zu\n", offsetof(typeof(a), x));
return 0;
}
zx2c4@thinkpad ~ $ gcc a.c
zx2c4@thinkpad ~ $ ./a.out
24
18

Jason