Messages in this thread | | | From | Stephan Mueller <> | Subject | Re: [BUG/PATCH] kernel RNG and its secrets | Date | Fri, 10 Apr 2015 16:09:10 +0200 |
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Am Freitag, 10. April 2015, 16:00:03 schrieb Hannes Frederic Sowa:
Hi Hannes,
>On Fr, 2015-04-10 at 15:25 +0200, Stephan Mueller wrote: >> I would like to bring up that topic again as I did some more analyses: >> >> For testing I used the following code: >> >> static inline void memset_secure(void *s, int c, size_t n) >> { >> >> memset(s, c, n); >> >> BARRIER >> >> } >> >> where BARRIER is defined as: >> >> (1) __asm__ __volatile__("" : "=r" (s) : "0" (s)); >> >> (2) __asm__ __volatile__("": : :"memory"); >> >> (3) __asm__ __volatile__("" : "=r" (s) : "0" (s) : "memory"); > >Hm, I wonder a little bit... > >Could you quickly test if you replace (s) with (n) just for the fun of >it? I don't know if we should ask clang people about that, at least it >is their goal to be as highly compatible with gcc inline asm.
Using
__asm__ __volatile__("" : "=r" (n) : "0" (n) : "memory");
clang O2/3: no mov
gcc O2/3: mov present
==> not good
Using __asm__ __volatile__("" : "=r" (n) : "0" (n));
clang O2/3: no mov
gcc O2/3: no mov
==> not good
What do you expect that change shall do?
> >Thanks for looking into this! > >Bye, >Hannes
Ciao Stephan
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