[PATCH] selftests/seccomp: fix pointer type mismatch in UPROBE test

[PATCH] selftests/seccomp: fix pointer type mismatch in UPROBE test

[Nirbhay Sharma]

Fix compilation error in UPROBE_setup caused by pointer type mismatch
in ternary expression. The probed_uretprobe and probed_uprobe function
pointers have different type attributes (__attribute__((nocf_check))),
which causes the conditional operator to fail with:

  seccomp_bpf.c:5175:74: error: pointer type mismatch in conditional
  expression [-Wincompatible-pointer-types]

Cast both function pointers to 'const void *' to match the expected
parameter type of get_uprobe_offset(), resolving the type mismatch
while preserving the function selection logic.

Signed-off-by: Nirbhay Sharma <nirbhay.lkd@gmail.com>
---
 tools/testing/selftests/seccomp/seccomp_bpf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 874f17763536..e13ffe18ef95 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -5172,7 +5172,8 @@ FIXTURE_SETUP(UPROBE)
 		ASSERT_GE(bit, 0);
 	}
 
-	offset = get_uprobe_offset(variant->uretprobe ? probed_uretprobe : probed_uprobe);
+	offset = get_uprobe_offset(variant->uretprobe ?
+		(const void *)probed_uretprobe : (const void *)probed_uprobe);
 	ASSERT_GE(offset, 0);
 
 	if (variant->uretprobe)
-- 
2.48.1

Re: [PATCH] selftests/seccomp: fix pointer type mismatch in UPROBE test

[Jiri Olsa]

On Sun, Oct 26, 2025 at 12:19:04AM +0530, Nirbhay Sharma wrote:
> Fix compilation error in UPROBE_setup caused by pointer type mismatch
> in ternary expression. The probed_uretprobe and probed_uprobe function
> pointers have different type attributes (__attribute__((nocf_check))),

just probed_uprobe right?

> which causes the conditional operator to fail with:
> 
>   seccomp_bpf.c:5175:74: error: pointer type mismatch in conditional
>   expression [-Wincompatible-pointer-types]

curious what compiler do you see that with? gcc-15 is silent,
the change looks good to me

thanks,
jirka


> 
> Cast both function pointers to 'const void *' to match the expected
> parameter type of get_uprobe_offset(), resolving the type mismatch
> while preserving the function selection logic.
> 
> Signed-off-by: Nirbhay Sharma <nirbhay.lkd@gmail.com>
> ---
>  tools/testing/selftests/seccomp/seccomp_bpf.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 874f17763536..e13ffe18ef95 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -5172,7 +5172,8 @@ FIXTURE_SETUP(UPROBE)
>  		ASSERT_GE(bit, 0);
>  	}
>  
> -	offset = get_uprobe_offset(variant->uretprobe ? probed_uretprobe : probed_uprobe);
> +	offset = get_uprobe_offset(variant->uretprobe ?
> +		(const void *)probed_uretprobe : (const void *)probed_uprobe);
>  	ASSERT_GE(offset, 0);
>  
>  	if (variant->uretprobe)
> -- 
> 2.48.1
> 
> 

Re: [PATCH] selftests/seccomp: fix pointer type mismatch in UPROBE test

[Sam James]

I tried to reproduce it with a small testcase and I could reproduce the
error with -fcf-protection and not without (where I get a warning that
the nocf_check attribute is ignored b/c of no flag).

Re: [PATCH] selftests/seccomp: fix pointer type mismatch in UPROBE test

[Nirbhay Sharma]

Hi Jiri,

Thank you for the review and for catching that inaccuracy!

On 10/26/25 2:48 AM, Jiri Olsa wrote:
> just probed_uprobe right?

Yes, you're absolutely correct. Only probed_uprobe has the
__attribute__((nocf_check)) attribute. I apologize for the confusion
in my original commit message. I'll fix this in v2.

> curious what compiler do you see that with?

I am seeing this error with Clang 19.1.2 on Fedora, which enables
-fcf-protection=full by default. As Sam confirmed, the error occurs
specifically when CFI protection is enabled via -fcf-protection. GCC
without this flag treats it as a warning or ignores the nocf_check
attribute entirely.

I'll send v2 with the corrected commit message.

Thanks again for the review!

Best regards,
Nirbhay

[PATCH v2] selftests/seccomp: fix pointer type mismatch in UPROBE test

[Nirbhay Sharma]

Fix compilation error in UPROBE_setup caused by pointer type mismatch
in the ternary expression when compiled with -fcf-protection. The
probed_uprobe function pointer has the __attribute__((nocf_check))
attribute, which causes the conditional operator to fail when combined
with the regular probed_uretprobe function pointer:

  seccomp_bpf.c:5175:74: error: pointer type mismatch in conditional
  expression [-Wincompatible-pointer-types]

Cast both function pointers to 'const void *' to match the expected
parameter type of get_uprobe_offset(), resolving the type mismatch
while preserving the function selection logic.

This error appears with compilers that enable Control Flow Integrity
(CFI) protection via -fcf-protection, such as Clang 19.1.2 (default
on Fedora).

Signed-off-by: Nirbhay Sharma <nirbhay.lkd@gmail.com>
---
 tools/testing/selftests/seccomp/seccomp_bpf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 874f17763536..e13ffe18ef95 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -5172,7 +5172,8 @@ FIXTURE_SETUP(UPROBE)
 		ASSERT_GE(bit, 0);
 	}
 
-	offset = get_uprobe_offset(variant->uretprobe ? probed_uretprobe : probed_uprobe);
+	offset = get_uprobe_offset(variant->uretprobe ?
+		(const void *)probed_uretprobe : (const void *)probed_uprobe);
 	ASSERT_GE(offset, 0);
 
 	if (variant->uretprobe)
-- 
2.48.1

Re: [PATCH v2] selftests/seccomp: fix pointer type mismatch in UPROBE test

[Sam James]

Nirbhay Sharma <nirbhay.lkd@gmail.com> writes:

> Fix compilation error in UPROBE_setup caused by pointer type mismatch
> in the ternary expression when compiled with -fcf-protection. The
> probed_uprobe function pointer has the __attribute__((nocf_check))
> attribute, which causes the conditional operator to fail when combined
> with the regular probed_uretprobe function pointer:
>

Just as a curiosity to share: I found a few tangential issues and
reported them as https://gcc.gnu.org/PR122427.

>   seccomp_bpf.c:5175:74: error: pointer type mismatch in conditional
>   expression [-Wincompatible-pointer-types]
>
> Cast both function pointers to 'const void *' to match the expected
> parameter type of get_uprobe_offset(), resolving the type mismatch
> while preserving the function selection logic.
>
> This error appears with compilers that enable Control Flow Integrity
> (CFI) protection via -fcf-protection, such as Clang 19.1.2 (default
> on Fedora).
>

Reviewed-by: Sam James <sam@gentoo.org>

> Signed-off-by: Nirbhay Sharma <nirbhay.lkd@gmail.com>
> ---
>  tools/testing/selftests/seccomp/seccomp_bpf.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 874f17763536..e13ffe18ef95 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -5172,7 +5172,8 @@ FIXTURE_SETUP(UPROBE)
>  		ASSERT_GE(bit, 0);
>  	}
>  
> -	offset = get_uprobe_offset(variant->uretprobe ? probed_uretprobe : probed_uprobe);
> +	offset = get_uprobe_offset(variant->uretprobe ?
> +		(const void *)probed_uretprobe : (const void *)probed_uprobe);
>  	ASSERT_GE(offset, 0);
>  
>  	if (variant->uretprobe)

Re: [PATCH v2] selftests/seccomp: fix pointer type mismatch in UPROBE test

[Jiri Olsa]

On Sun, Oct 26, 2025 at 02:42:33PM +0530, Nirbhay Sharma wrote:
> Fix compilation error in UPROBE_setup caused by pointer type mismatch
> in the ternary expression when compiled with -fcf-protection. The
> probed_uprobe function pointer has the __attribute__((nocf_check))
> attribute, which causes the conditional operator to fail when combined
> with the regular probed_uretprobe function pointer:
> 
>   seccomp_bpf.c:5175:74: error: pointer type mismatch in conditional
>   expression [-Wincompatible-pointer-types]
> 
> Cast both function pointers to 'const void *' to match the expected
> parameter type of get_uprobe_offset(), resolving the type mismatch
> while preserving the function selection logic.
> 
> This error appears with compilers that enable Control Flow Integrity
> (CFI) protection via -fcf-protection, such as Clang 19.1.2 (default
> on Fedora).
> 
> Signed-off-by: Nirbhay Sharma <nirbhay.lkd@gmail.com>

Reviwed-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka

> ---
>  tools/testing/selftests/seccomp/seccomp_bpf.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index 874f17763536..e13ffe18ef95 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -5172,7 +5172,8 @@ FIXTURE_SETUP(UPROBE)
>  		ASSERT_GE(bit, 0);
>  	}
>  
> -	offset = get_uprobe_offset(variant->uretprobe ? probed_uretprobe : probed_uprobe);
> +	offset = get_uprobe_offset(variant->uretprobe ?
> +		(const void *)probed_uretprobe : (const void *)probed_uprobe);
>  	ASSERT_GE(offset, 0);
>  
>  	if (variant->uretprobe)
> -- 
> 2.48.1
>