latent_entropy: Mark functions with __latent_entropy

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>

2 files changed, 2 insertions, 2 deletions

diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index 944b1b491ed8..1898559e6b60 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -170,7 +170,7 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
                                       false));
 }
 
-static void rcu_process_callbacks(struct softirq_action *unused)
+static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused)
 {
         __rcu_process_callbacks(&rcu_sched_ctrlblk);
         __rcu_process_callbacks(&rcu_bh_ctrlblk);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 5d80925e7fc8..e5164deb51e1 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3013,7 +3013,7 @@ __rcu_process_callbacks(struct rcu_state *rsp)
 /*
  * Do RCU core processing for the current CPU.
  */
-static void rcu_process_callbacks(struct softirq_action *unused)
+static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused)
 {
         struct rcu_state *rsp;