Re: [PATCH] kunit: fix longest symbol length test

[Nathan Chancellor <nathan@kernel.org>]

Hi Sergio,

On Sun, Apr 27, 2025 at 09:10:09PM +0200, Sergio González Collado wrote:
> The kunit test that checks the longests symbol length [1], has triggered
> warnings in some CI pilelines when symbol prefixes are used [2]. The test
> is adjusted to depend on !CONFIG_PREFIX_SYMBOLS as sujested in [3].
> 
> [1] https://lore.kernel.org/rust-for-linux/CABVgOSm=5Q0fM6neBhxSbOUHBgNzmwf2V22vsYC10YRBT=kN1g@mail.gmail.com/T/#t
> [2] https://lore.kernel.org/all/20250328112156.2614513-1-arnd@kernel.org/T/#u
> [3] https://lore.kernel.org/all/ycgbf7jcq7nc62ndqiynogt6hkabgl3hld4uyelgo7rksylf32@oysq7jpchtp4/
> 
> Fixes: c104c16073b7 ("Kunit to check the longest symbol length")
> Signed-off-by: Sergio González Collado <sergio.collado@gmail.com>
> ---
>  lib/Kconfig.debug                | 2 +-
>  lib/tests/longest_symbol_kunit.c | 3 +--
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index f9051ab610d5..6937dedce04d 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2885,7 +2885,7 @@ config FORTIFY_KUNIT_TEST
>  
>  config LONGEST_SYM_KUNIT_TEST
>  	tristate "Test the longest symbol possible" if !KUNIT_ALL_TESTS
> -	depends on KUNIT && KPROBES
> +	depends on KUNIT && KPROBES && !CONFIG_PREFIX_SYMBOLS

This should be !PREFIX_SYMBOLS, otherwise it would be looking for a
CONFIG_CONFIG_PREFIX_SYMBOLS not to exist, which will always be true.

This solution does not appear to take into account Peter's comment
around how kCFI will prefix these symbols as well? Should it depend on
!CFI_CLANG as well?

https://lore.kernel.org/20250411065054.GM9833@noisy.programming.kicks-ass.net/

>  	default KUNIT_ALL_TESTS
>  	help
>  	  Tests the longest symbol possible
> diff --git a/lib/tests/longest_symbol_kunit.c b/lib/tests/longest_symbol_kunit.c
> index e3c28ff1807f..b183fb92d1b2 100644
> --- a/lib/tests/longest_symbol_kunit.c
> +++ b/lib/tests/longest_symbol_kunit.c
> @@ -3,8 +3,7 @@
>   * Test the longest symbol length. Execute with:
>   *  ./tools/testing/kunit/kunit.py run longest-symbol
>   *  --arch=x86_64 --kconfig_add CONFIG_KPROBES=y --kconfig_add CONFIG_MODULES=y
> - *  --kconfig_add CONFIG_RETPOLINE=n --kconfig_add CONFIG_CFI_CLANG=n
> - *  --kconfig_add CONFIG_MITIGATION_RETPOLINE=n
> + *  --kconfig_add CONFIG_CPU_MITIGATIONS=n
>   */
>  
>  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> 
> base-commit: f1a3944c860b0615d0513110d8cf62bb94adbb41
> -- 
> 2.39.2
>