latent_entropy: provide userspace visibility

Commit Message

Kees Cook June 18, 2016, 6:03 p.m. UTC

This is just a toy to look at the latent_entropy value as it changes
from userspace. Not intended for actual use...

Signed-off-by: Kees Cook <[e-mail]>
---
 kernel/ksysfs.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Patch

diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index 152da4a48867..64aed735098a 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -180,6 +180,15 @@  static ssize_t rcu_normal_store(struct kobject *kobj,
 KERNEL_ATTR_RW(rcu_normal);
 #endif /* #ifndef CONFIG_TINY_RCU */
 
+#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
+static ssize_t latent_entropy_show(struct kobject *kobj,
+				   struct kobj_attribute *attr, char *buf)
+{
+	return sprintf(buf, "0x%08llx\n", latent_entropy);
+}
+KERNEL_ATTR_RO(latent_entropy);
+#endif
+
 /*
  * Make /sys/kernel/notes give the raw contents of our kernel .notes section.
  */
@@ -225,6 +234,9 @@  static struct attribute * kernel_attrs[] = {
 	&rcu_expedited_attr.attr,
 	&rcu_normal_attr.attr,
 #endif
+#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
+	&latent_entropy_attr.attr,
+#endif
 	NULL
 };