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>
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 573c5a1..432f5c9 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -188,6 +188,13 @@
#endif /* GCC_VERSION >= 40300 */
#if GCC_VERSION >= 40500
+
+#ifndef __CHECKER__
+#ifdef LATENT_ENTROPY_PLUGIN
+#define __latent_entropy __attribute__((latent_entropy))
+#endif
+#endif
+
/*
* Mark a position in code as unreachable. This can be used to
* suppress control flow warnings after asm blocks that transfer
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 6685698..ceaddaf 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -406,6 +406,10 @@
# 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.
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index 5295535..9852c7e 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -105,7 +105,7 @@
void put_files_struct(struct files_struct *fs);
void reset_files_struct(struct files_struct *);
int unshare_files(struct files_struct **);
-struct files_struct *dup_fd(struct files_struct *, int *);
+struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy;
void do_close_on_exec(struct files_struct *);
int iterate_fd(struct files_struct *, unsigned,
int (*)(const void *, struct file *, unsigned),
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 1dbf52f..e0341af 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -437,7 +437,7 @@
extern unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask);
/* drivers/char/random.c */
-extern void add_disk_randomness(struct gendisk *disk);
+extern void add_disk_randomness(struct gendisk *disk) __latent_entropy;
extern void rand_initialize_disk(struct gendisk *disk);
static inline sector_t get_start_sect(struct block_device *bdev)
diff --git a/include/linux/init.h b/include/linux/init.h
index 6935d02..1e5c131 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -39,7 +39,7 @@
/* These are for everybody (although not all archs will actually
discard it in modules) */
-#define __init __section(.init.text) __cold notrace
+#define __init __section(.init.text) __cold notrace __latent_entropy
#define __initdata __section(.init.data)
#define __initconst __constsection(.init.rodata)
#define __exitdata __section(.exit.data)
@@ -86,7 +86,8 @@
#define __exit __section(.exit.text) __exitused __cold notrace
/* Used for MEMORY_HOTPLUG */
-#define __meminit __section(.meminit.text) __cold notrace
+#define __meminit __section(.meminit.text) __cold notrace \
+ __latent_entropy
#define __meminitdata __section(.meminit.data)
#define __meminitconst __constsection(.meminit.rodata)
#define __memexit __section(.memexit.text) __exitused __cold notrace
diff --git a/include/linux/random.h b/include/linux/random.h
index a59c74c..d80a438 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -30,8 +30,8 @@
#endif
extern void add_input_randomness(unsigned int type, unsigned int code,
- unsigned int value);
-extern void add_interrupt_randomness(int irq, int irq_flags);
+ unsigned int value) __latent_entropy;
+extern void add_interrupt_randomness(int irq, int irq_flags) __latent_entropy;
extern void get_random_bytes(void *buf, int nbytes);
extern int add_random_ready_callback(struct random_ready_callback *rdy);