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latent_entropy: Mark functions with __latent_entropy

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The __latent_entropy gcc attribute can be used only on functions and
variables.  If it is on a function then the plugin will instrument it for
gathering control-flow entropy. If the attribute is on a variable then
the plugin will initialize it with random contents.  The variable must
be an integer, an integer array type or a structure with integer fields.

These specific functions have been selected because they are init
functions (to help gather boot-time entropy), are called at unpredictable
times, or they have variable loops, each of which provide some level of
latent entropy.

Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message]
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Emese Revfy 2016-06-20 20:42:34 +02:00 • committed by Kees Cook
parent 38addce8b6
commit 0766f788eb
19 changed files with 37 additions and 22 deletions
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4
include/linux/compiler.h
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@ -406,6 +406,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
# define __attribute_const__ /* unimplemented */
#endif
#ifndef __latent_entropy
# define __latent_entropy
#endif
/*
* Tell gcc if a function is cold. The compiler will assume any path
* directly leading to the call is unlikely.