Re: [BUG/PATCH] kernel RNG and its secrets

From: Daniel Borkmann
Date: Mon Apr 27 2015 - 16:34:45 EST

On 04/27/2015 09:10 PM, Stephan Mueller wrote:
I posted the issue on the clang mailing list on April 10 -- no word so far. I
would interpret this as a sign that it is a no-issue for them.

Hm. ;)

Here's a bug report on the topic, gcc vs llvm:

Lets add a new barrier macro to linux/compiler{,-gcc}.h, f.e.

#define barrier_data(ptr) __asm__ __volatile__("" : : "r" (ptr) : "memory")

or the version Mancha proposed. You could wrap that ...

#define OPTIMIZER_HIDE(ptr) barrier_data(ptr)

... and use that one for memzero_explicit() instead:

void memzero_explicit(void *s, size_t count)
memset(s, 0, count);

It certainly needs comments explaining in what situations to use
which OPTIMIZER_HIDE* variants, etc.

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