[PATCH V3] livepatch: non static warnings fix

[PATCH V3] livepatch: non static warnings fix

[Nicholas Mc Guire]

Sparse reported warnings about non-static symbols. For the variables
a simple static attribute is fine - for the functions referenced by
livepatch via klp_func the symbol-names must be unmodified in the
symbol table and the patchable code has to be emitted. The resolution
is to attach __used attribute to the shared statically declared functions.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Suggested-by: Joe Lawrence <joe.lawrence@redhat.com>
Link: https://lkml.org/lkml/2018/12/13/827
---

V2: not all static functions shared need to carry the __noclone
    attribute only those that need to be resolved at runtime by
    livepatch - so drop the unnecessary __noclone attributes as
    well as the Note on __noclone as suggested by Joe Lawrence
    <joe.lawrence@redhat.com> - thanks !

V3: fix the wording as proposed by Joe Lawrence
    <joe.lawrence@redhat.com> to address that this is not only
    about how to fix sparse warnings but also to ensure
    traceable/patchable code still being emitted.

Sparse reported the following findings in 5.0-rc3:

  CHECK   samples/livepatch/livepatch-shadow-mod.c
samples/livepatch/livepatch-shadow-mod.c:99:1: warning: symbol 'dummy_list' was not declared. Should it be static?
samples/livepatch/livepatch-shadow-mod.c:100:1: warning: symbol 'dummy_list_mutex' was not declared. Should it be static?
samples/livepatch/livepatch-shadow-mod.c:107:23: warning: symbol 'dummy_alloc' was not declared. Should it be static?
samples/livepatch/livepatch-shadow-mod.c:132:15: warning: symbol 'dummy_free' was not declared. Should it be static?
samples/livepatch/livepatch-shadow-mod.c:140:15: warning: symbol 'dummy_check' was not declared. Should it be static?

  CHECK   samples/livepatch/livepatch-shadow-fix1.c
samples/livepatch/livepatch-shadow-fix1.c:74:14: warning: symbol 'livepatch_fix1_dummy_alloc' was not declared. Should it be static?
samples/livepatch/livepatch-shadow-fix1.c:116:6: warning: symbol 'livepatch_fix1_dummy_free' was not declared. Should it be static?

  CHECK   samples/livepatch/livepatch-shadow-fix2.c
samples/livepatch/livepatch-shadow-fix2.c:53:6: warning: symbol 'livepatch_fix2_dummy_check' was not declared. Should it be static?
samples/livepatch/livepatch-shadow-fix2.c:81:6: warning: symbol 'livepatch_fix2_dummy_free' was not declared. Should it be static?

Patch was compile tested with: x86_64_defconfig + FTRACE=y
FUNCTION_TRACER=y, SAMPLES=y, LIVEPATCH=y SAMPLE_LIVEPATCH=m
(looks sparse, smatch claan, one coccichek warning left - fix later today)

Patch was runtested with:
   insmod samples/livepatch/livepatch-shadow-mod.ko
   insmod samples/livepatch/livepatch-shadow-fix1.ko
   insmod samples/livepatch/livepatch-shadow-fix2.ko
   echo 0 > /sys/kernel/livepatch/livepatch_shadow_fix2/enabled
   echo 0 > /sys/kernel/livepatch/livepatch_shadow_fix1/enabled
   rmmod livepatch-shadow-fix2
   rmmod livepatch-shadow-fix1
   rmmod livepatch-shadow-mod
and dmesg output compared to previous run.

Patch is against 5.0-rc3 (localversion-next is next-20190123)

 samples/livepatch/livepatch-shadow-fix1.c |  4 ++--
 samples/livepatch/livepatch-shadow-fix2.c |  4 ++--
 samples/livepatch/livepatch-shadow-mod.c  | 11 ++++++-----
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/samples/livepatch/livepatch-shadow-fix1.c b/samples/livepatch/livepatch-shadow-fix1.c
index a5a5cac..67a73e5 100644
--- a/samples/livepatch/livepatch-shadow-fix1.c
+++ b/samples/livepatch/livepatch-shadow-fix1.c
@@ -71,7 +71,7 @@ static int shadow_leak_ctor(void *obj, void *shadow_data, void *ctor_data)
 	return 0;
 }
 
-struct dummy *livepatch_fix1_dummy_alloc(void)
+static struct dummy *livepatch_fix1_dummy_alloc(void)
 {
 	struct dummy *d;
 	void *leak;
@@ -113,7 +113,7 @@ static void livepatch_fix1_dummy_leak_dtor(void *obj, void *shadow_data)
 			 __func__, d, *shadow_leak);
 }
 
-void livepatch_fix1_dummy_free(struct dummy *d)
+static void livepatch_fix1_dummy_free(struct dummy *d)
 {
 	void **shadow_leak;
 
diff --git a/samples/livepatch/livepatch-shadow-fix2.c b/samples/livepatch/livepatch-shadow-fix2.c
index 52de947..91c21d5 100644
--- a/samples/livepatch/livepatch-shadow-fix2.c
+++ b/samples/livepatch/livepatch-shadow-fix2.c
@@ -50,7 +50,7 @@ struct dummy {
 	unsigned long jiffies_expire;
 };
 
-bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
+static bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
 {
 	int *shadow_count;
 
@@ -78,7 +78,7 @@ static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)
 			 __func__, d, *shadow_leak);
 }
 
-void livepatch_fix2_dummy_free(struct dummy *d)
+static void livepatch_fix2_dummy_free(struct dummy *d)
 {
 	void **shadow_leak;
 	int *shadow_count;
diff --git a/samples/livepatch/livepatch-shadow-mod.c b/samples/livepatch/livepatch-shadow-mod.c
index 4aa8a88..4d79c6dc 100644
--- a/samples/livepatch/livepatch-shadow-mod.c
+++ b/samples/livepatch/livepatch-shadow-mod.c
@@ -96,15 +96,15 @@ MODULE_DESCRIPTION("Buggy module for shadow variable demo");
  * Keep a list of all the dummies so we can clean up any residual ones
  * on module exit
  */
-LIST_HEAD(dummy_list);
-DEFINE_MUTEX(dummy_list_mutex);
+static LIST_HEAD(dummy_list);
+static DEFINE_MUTEX(dummy_list_mutex);
 
 struct dummy {
 	struct list_head list;
 	unsigned long jiffies_expire;
 };
 
-noinline struct dummy *dummy_alloc(void)
+static __used noinline struct dummy *dummy_alloc(void)
 {
 	struct dummy *d;
 	void *leak;
@@ -129,7 +129,7 @@ noinline struct dummy *dummy_alloc(void)
 	return d;
 }
 
-noinline void dummy_free(struct dummy *d)
+static __used noinline void dummy_free(struct dummy *d)
 {
 	pr_info("%s: dummy @ %p, expired = %lx\n",
 		__func__, d, d->jiffies_expire);
@@ -137,7 +137,8 @@ noinline void dummy_free(struct dummy *d)
 	kfree(d);
 }
 
-noinline bool dummy_check(struct dummy *d, unsigned long jiffies)
+static __used noinline bool dummy_check(struct dummy *d,
+					   unsigned long jiffies)
 {
 	return time_after(jiffies, d->jiffies_expire);
 }
-- 
2.1.4

Re: [PATCH V3] livepatch: non static warnings fix

[Miroslav Benes]

Hi,

On Wed, 23 Jan 2019, Nicholas Mc Guire wrote:

> Sparse reported warnings about non-static symbols. For the variables
> a simple static attribute is fine - for the functions referenced by
> livepatch via klp_func the symbol-names must be unmodified in the
> symbol table and the patchable code has to be emitted. The resolution
> is to attach __used attribute to the shared statically declared functions.
> 
> Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
> Suggested-by: Joe Lawrence <joe.lawrence@redhat.com>
> Link: https://lkml.org/lkml/2018/12/13/827

could you reorder the tags and change Link: tag to 
https://lkml.kernel.org/r/<message_id> as asked for when we reviewed v2?

With that

Acked-by: Miroslav Benes <mbenes@suse.cz>

M

Re: [PATCH V3] livepatch: non static warnings fix

[Nicholas Mc Guire]

On Wed, Jan 23, 2019 at 03:30:57PM +0100, Miroslav Benes wrote:
> Hi,
> 
> On Wed, 23 Jan 2019, Nicholas Mc Guire wrote:
> 
> > Sparse reported warnings about non-static symbols. For the variables
> > a simple static attribute is fine - for the functions referenced by
> > livepatch via klp_func the symbol-names must be unmodified in the
> > symbol table and the patchable code has to be emitted. The resolution
> > is to attach __used attribute to the shared statically declared functions.
> > 
> > Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
> > Suggested-by: Joe Lawrence <joe.lawrence@redhat.com>
> > Link: https://lkml.org/lkml/2018/12/13/827
> 
> could you reorder the tags and change Link: tag to 
> https://lkml.kernel.org/r/<message_id> as asked for when we reviewed v2?
>

sorry overlooked that - yes will fix that up and resend

thx!
hofrat

 
> With that
> 
> Acked-by: Miroslav Benes <mbenes@suse.cz>
> 
> M

Re: [PATCH V3] livepatch: non static warnings fix

[Petr Mladek]

On Wed 2019-01-23 15:30:57, Miroslav Benes wrote:
> Hi,
> 
> On Wed, 23 Jan 2019, Nicholas Mc Guire wrote:
> 
> > Sparse reported warnings about non-static symbols. For the variables
> > a simple static attribute is fine - for the functions referenced by
> > livepatch via klp_func the symbol-names must be unmodified in the
> > symbol table and the patchable code has to be emitted. The resolution
> > is to attach __used attribute to the shared statically declared functions.
> > 
> > Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
> > Suggested-by: Joe Lawrence <joe.lawrence@redhat.com>
> > Link: https://lkml.org/lkml/2018/12/13/827
> 
> could you reorder the tags and change Link: tag to 
> https://lkml.kernel.org/r/<message_id> as asked for when we reviewed v2?

Just for record. My understanding is that the Link: tag usually points
to the mail with the final patch that was pushed.

It means that it is usually added by the maintainer and not the patch
sender.

Best Regards,
Petr