[PATCH] Fix implicit cast warning in test_klp_state.c

[PATCH] Fix implicit cast warning in test_klp_state.c

[Shresth Prasad]

    The function `klp_get_state` returns an `int` value, but the variable
    `loglevel_state` is of type `struct klp_state *` and thus does an
    implicit cast. Explicitly casting these values fixes:

            - warning: assignment to ‘struct klp_state *’ from ‘int’
	    makes pointer from integer without a cast [-Wint-conversion]

    on lines 38, 55, 68 and 80 of test_klp_state.c

Signed-off-by: Shresth Prasad <shresthprasad7@gmail.com>
---
 .../selftests/livepatch/test_modules/test_klp_state.c     | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/livepatch/test_modules/test_klp_state.c b/tools/testing/selftests/livepatch/test_modules/test_klp_state.c
index 57a4253acb01..ae6b1ca15fc0 100644
--- a/tools/testing/selftests/livepatch/test_modules/test_klp_state.c
+++ b/tools/testing/selftests/livepatch/test_modules/test_klp_state.c
@@ -35,7 +35,7 @@ static int allocate_loglevel_state(void)
 {
 	struct klp_state *loglevel_state;
 
-	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
+	loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
 	if (!loglevel_state)
 		return -EINVAL;
 
@@ -52,7 +52,7 @@ static void fix_console_loglevel(void)
 {
 	struct klp_state *loglevel_state;
 
-	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
+	loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
 	if (!loglevel_state)
 		return;
 
@@ -65,7 +65,7 @@ static void restore_console_loglevel(void)
 {
 	struct klp_state *loglevel_state;
 
-	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
+	loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
 	if (!loglevel_state)
 		return;
 
@@ -77,7 +77,7 @@ static void free_loglevel_state(void)
 {
 	struct klp_state *loglevel_state;
 
-	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
+	loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
 	if (!loglevel_state)
 		return;
 
-- 
2.43.1

Re: [PATCH] Fix implicit cast warning in test_klp_state.c

[Marcos Paulo de Souza]

On Sat, 17 Feb 2024 04:21:26 +0530 Shresth Prasad <shresthprasad7@gmail.com> wrote:

>     The function `klp_get_state` returns an `int` value, but the variable
>     `loglevel_state` is of type `struct klp_state *` and thus does an
>     implicit cast. Explicitly casting these values fixes:
> 
>             - warning: assignment to \u2018struct klp_state *\u2019 from \u2018int\u2019
> 	    makes pointer from integer without a cast [-Wint-conversion]
> 
>     on lines 38, 55, 68 and 80 of test_klp_state.c

I was unable to find where you saw the klp_get_state returning int. I tried
searching at the current master of live-patching repo[1], on linux-next. Can
you point where do you saw it? For me, klp_get_state return a pointer to klp_state.

Thanks,
  Marcos

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching.git/tree/kernel/livepatch/state.c

> 
> Signed-off-by: Shresth Prasad <shresthprasad7@gmail.com>
> ---
>  .../selftests/livepatch/test_modules/test_klp_state.c     | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/livepatch/test_modules/test_klp_state.c b/tools/testing/selftests/livepatch/test_modules/test_klp_state.c
> index 57a4253acb01..ae6b1ca15fc0 100644
> --- a/tools/testing/selftests/livepatch/test_modules/test_klp_state.c
> +++ b/tools/testing/selftests/livepatch/test_modules/test_klp_state.c
> @@ -35,7 +35,7 @@ static int allocate_loglevel_state(void)
>  {
>  	struct klp_state *loglevel_state;
>  
> -	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
> +	loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>  	if (!loglevel_state)
>  		return -EINVAL;
>  
> @@ -52,7 +52,7 @@ static void fix_console_loglevel(void)
>  {
>  	struct klp_state *loglevel_state;
>  
> -	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
> +	loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>  	if (!loglevel_state)
>  		return;
>  
> @@ -65,7 +65,7 @@ static void restore_console_loglevel(void)
>  {
>  	struct klp_state *loglevel_state;
>  
> -	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
> +	loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>  	if (!loglevel_state)
>  		return;
>  
> @@ -77,7 +77,7 @@ static void free_loglevel_state(void)
>  {
>  	struct klp_state *loglevel_state;
>  
> -	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
> +	loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>  	if (!loglevel_state)
>  		return;
>  
> -- 
> 2.43.1

Re: [PATCH] Fix implicit cast warning in test_klp_state.c

[zhang warden]

Well, the repo location I use is git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git.
It seem klp_get_state return struct klp_state.
The definition of this function in my repo as follows:

struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id) 
{
    struct klp_state *state;

    klp_for_each_state(patch, state) {
        if (state->id == id) 
            return state;
    }   

    return NULL;
}
EXPORT_SYMBOL_GPL(klp_get_state);

Are you sure there is really a need for forced conversion?

> 2024年2月19日 22:16，Marcos Paulo de Souza <mpdesouza@suse.com> 写道：
> 
> On Sat, 17 Feb 2024 04:21:26 +0530 Shresth Prasad <shresthprasad7@gmail.com> wrote:
> 
>>    The function `klp_get_state` returns an `int` value, but the variable
>>    `loglevel_state` is of type `struct klp_state *` and thus does an
>>    implicit cast. Explicitly casting these values fixes:
>> 
>>            - warning: assignment to \u2018struct klp_state *\u2019 from \u2018int\u2019
>>    makes pointer from integer without a cast [-Wint-conversion]
>> 
>>    on lines 38, 55, 68 and 80 of test_klp_state.c
> 
> I was unable to find where you saw the klp_get_state returning int. I tried
> searching at the current master of live-patching repo[1], on linux-next. Can
> you point where do you saw it? For me, klp_get_state return a pointer to klp_state.
> 
> Thanks,
>  Marcos
> 
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching.git/tree/kernel/livepatch/state.c
> 
>> 
>> Signed-off-by: Shresth Prasad <shresthprasad7@gmail.com>
>> ---
>> .../selftests/livepatch/test_modules/test_klp_state.c     | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>> 
>> diff --git a/tools/testing/selftests/livepatch/test_modules/test_klp_state.c b/tools/testing/selftests/livepatch/test_modules/test_klp_state.c
>> index 57a4253acb01..ae6b1ca15fc0 100644
>> --- a/tools/testing/selftests/livepatch/test_modules/test_klp_state.c
>> +++ b/tools/testing/selftests/livepatch/test_modules/test_klp_state.c
>> @@ -35,7 +35,7 @@ static int allocate_loglevel_state(void)
>> {
>> struct klp_state *loglevel_state;
>> 
>> - loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>> + loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>> if (!loglevel_state)
>> return -EINVAL;
>> 
>> @@ -52,7 +52,7 @@ static void fix_console_loglevel(void)
>> {
>> struct klp_state *loglevel_state;
>> 
>> - loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>> + loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>> if (!loglevel_state)
>> return;
>> 
>> @@ -65,7 +65,7 @@ static void restore_console_loglevel(void)
>> {
>> struct klp_state *loglevel_state;
>> 
>> - loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>> + loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>> if (!loglevel_state)
>> return;
>> 
>> @@ -77,7 +77,7 @@ static void free_loglevel_state(void)
>> {
>> struct klp_state *loglevel_state;
>> 
>> - loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>> + loglevel_state = (struct klp_state *)klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>> if (!loglevel_state)
>> return;
>> 
>> -- 
>> 2.43.1
> 

Re: [PATCH] Fix implicit cast warning in test_klp_state.c

[Shresth Prasad]

Looking at the function definition now, I do see that the function returns a struct pointer but for me the compiler still complains about an implicit conversion from int to struct pointer.

Is there any particular reason why this might be happening? I couldn't quite figure it out myself as I am very new to working with the kernel.

Regards,
Shresth

Re: [PATCH] Fix implicit cast warning in test_klp_state.c

[Marcos Paulo de Souza]

On Tue, 20 Feb 2024 17:23:49 +0530 (GMT+05:30) Shresth Prasad <shresthprasad7@gmail.com> wrote:

> Looking at the function definition now, I do see that the function returns a struct pointer but for me the compiler still complains about an implicit conversion from int to struct pointer.
> 
> Is there any particular reason why this might be happening? I couldn't quite figure it out myself as I am very new to working with the kernel.

What compiler version and architecture? Are you compiling using flags like W=1?
I would advise you to always add more information about how the problem
manifests, and what you are executing. This can help to nail down the issue
quicker.

Thanks,
  Marcos

> 
> Regards,
> Shresth

Re: [PATCH] Fix implicit cast warning in test_klp_state.c

[Shresth Prasad]

>What compiler version and architecture? Are you >compiling using flags like W=1?
>I would advise you to always add more information >about how the problem
>manifests, and what you are executing. This can >help to nail down the issue quicker.

I'll keep that in mind. I'm on an x86_64 system with gcc version 13.2.1 20230801.

I'm using the command `make -j15 -C tools/testing/selftests` with no additional flags.

Regards,
Shresth

Re: [PATCH] Fix implicit cast warning in test_klp_state.c

[zhang warden]

Would you please pasting the original warning of your complier? 
And did you check your source code if your source code is the the latest version?

Regards,
Warden

> On Feb 20, 2024, at 21:20, Shresth Prasad <shresthprasad7@gmail.com> wrote:
> 
>> What compiler version and architecture? Are you >compiling using flags like W=1?
>> I would advise you to always add more information >about how the problem
>> manifests, and what you are executing. This can >help to nail down the issue quicker.
> 
> I'll keep that in mind. I'm on an x86_64 system with gcc version 13.2.1 20230801.
> 
> I'm using the command `make -j15 -C tools/testing/selftests` with no additional flags.
> 
> Regards,
> Shresth

Re: [PATCH] Fix implicit cast warning in test_klp_state.c

[Shresth Prasad]

I checked the source code and yes I am on the latest Linux next repo.

Here's the warning:
/home/shresthp/dev/linux_work/linux_next/tools/testing/selftests/livepatch/test_modules/test_klp_state.c:38:24: warning: assignment to ‘struct klp_state *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
   38 |         loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
      |                        ^
/home/shresthp/dev/linux_work/linux_next/tools/testing/selftests/livepatch/test_modules/test_klp_state.c: In function ‘fix_console_loglevel’:
/home/shresthp/dev/linux_work/linux_next/tools/testing/selftests/livepatch/test_modules/test_klp_state.c:55:24: warning: assignment to ‘struct klp_state *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
   55 |         loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
      |                        ^
/home/shresthp/dev/linux_work/linux_next/tools/testing/selftests/livepatch/test_modules/test_klp_state.c: In function ‘restore_console_loglevel’:
/home/shresthp/dev/linux_work/linux_next/tools/testing/selftests/livepatch/test_modules/test_klp_state.c:68:24: warning: assignment to ‘struct klp_state *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
   68 |         loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
      |                        ^
/home/shresthp/dev/linux_work/linux_next/tools/testing/selftests/livepatch/test_modules/test_klp_state.c: In function ‘free_loglevel_state’:
/home/shresthp/dev/linux_work/linux_next/tools/testing/selftests/livepatch/test_modules/test_klp_state.c:80:24: warning: assignment to ‘struct klp_state *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
   80 |         loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
      |                        ^

Thank you for your help so far.

Regards,
Shresth

Re: [PATCH] Fix implicit cast warning in test_klp_state.c

[Nicolai Stange]

Shresth Prasad <shresthprasad7@gmail.com> writes:

> I checked the source code and yes I am on the latest Linux next repo.
>
> Here's the warning:
> /home/shresthp/dev/linux_work/linux_next/tools/testing/selftests/livepatch/test_modules/test_klp_state.c:38:24: warning: assignment to ‘struct klp_state *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
>    38 |         loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>       |                        ^


Is the declaration of klp_get_state() visible at that point, i.e. is
there perhaps any warning about missing declarations above that?

Otherwise C rules would default to assume an 'int' return type.

Thanks,

Nicolai

-- 
SUSE Software Solutions Germany GmbH, Frankenstraße 146, 90461 Nürnberg, Germany
GF: Ivo Totev, Andrew McDonald, Werner Knoblich
(HRB 36809, AG Nürnberg)

Re: [PATCH] Fix implicit cast warning in test_klp_state.c

[Shresth Prasad]

>Is the declaration of klp_get_state() visible at that >point, i.e. is
>there perhaps any warning about missing >declarations above that?
>
>Otherwise C rules would default to assume an 'int' >return type.

I wasn't aware it works like that. You're right I do see some warnings about implicit function declarations of klp_get_state.

Regards,
Shresth

Re: [PATCH] Fix implicit cast warning in test_klp_state.c

[Joe Lawrence]

On 2/21/24 07:44, Nicolai Stange wrote:
> Shresth Prasad <shresthprasad7@gmail.com> writes:
> 
>> I checked the source code and yes I am on the latest Linux next repo.
>>
>> Here's the warning:
>> /home/shresthp/dev/linux_work/linux_next/tools/testing/selftests/livepatch/test_modules/test_klp_state.c:38:24: warning: assignment to ‘struct klp_state *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
>>    38 |         loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
>>       |                        ^
> 
> 
> Is the declaration of klp_get_state() visible at that point, i.e. is
> there perhaps any warning about missing declarations above that?
> 
> Otherwise C rules would default to assume an 'int' return type.
> 

This is an interesting clue.  I thought I might be able to reproduce the
build error by modifying include/livepatch.h and running `make -j15 -C
tools/testing/selftests/livepatch` ... but that seemed to work fine on
my system.  I even removed the entire include/ subdir from my tree and
it still built the test module.  Huh?

Then I moved /lib/modules/$(uname -r)/build out of the way and saw that
the compilation failed.  Ah hah -- that's right, it's using the system
build tree.  That version of livepatch.h may have a missing or
completely different definition of klp_get_state().

How does this sequence work for you, Shresth:

  # Verify that kernel livepatching is turned on
  $ grep LIVEPATCH .config
  CONFIG_HAVE_LIVEPATCH=y
  CONFIG_LIVEPATCH=y

  # Build linux-next kernel tree and then the livepatch selftests,
  # pointing KDIR to this tree
  $ make -j$(nproc) vmlinux && \
    make -j$(nproc) KDIR=$(pwd) -C tools/testing/selftests/livepatch

-- 
Joe

Re: [PATCH] Fix implicit cast warning in test_klp_state.c

[Shresth Prasad]

That sequence of steps fixed the warnings. Thank you so much!

Regards,
Shresth