linux-kernel - Re: [PATCH] drm/xe: replace basename() with portable strrchr()

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Message-ID: <peqczm4644mskitmvsq5b2t4r4rs3beei7li3p7uw2nhjne6h6@a3mztccaxfey>
Date: Wed, 20 Aug 2025 16:15:47 -0500
From: Lucas De Marchi <lucas.demarchi@...el.com>
To: Carlos Llamas <cmllamas@...gle.com>
CC: Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>, David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>, Matt Atwood <matthew.s.atwood@...el.com>,
	<kernel-team@...roid.com>, <linux-kernel@...r.kernel.org>, "open list:INTEL
 DRM XE DRIVER (Lunar Lake and newer)" <intel-xe@...ts.freedesktop.org>, "open
 list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/xe: replace basename() with portable strrchr()

On Wed, Aug 20, 2025 at 08:16:11PM +0000, Carlos Llamas wrote:
>Commit b0a2ee5567ab ("drm/xe: prepare xe_gen_wa_oob to be multi-use")
>introduced a call to basename(). The GNU version of this function is not
>portable and fails to build with alternative libc implementations like
>musl or bionic. This causes the following build error:
>
>  drivers/gpu/drm/xe/xe_gen_wa_oob.c:130:12: error: assignment to ‘const char *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
>    130 |         fn = basename(fn);
>        |            ^
>
>While a POSIX version of basename() could be used, it would require a
>separate header plus the behavior differs from GNU version in that it
>might modify its argument. Not great.
>
>Instead replace basename() with a strrchr() based implementation which
>provides the same functionality and avoid portability issues.
>
>Fixes: b0a2ee5567ab ("drm/xe: prepare xe_gen_wa_oob to be multi-use")
>Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
>---
> drivers/gpu/drm/xe/xe_gen_wa_oob.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/gpu/drm/xe/xe_gen_wa_oob.c b/drivers/gpu/drm/xe/xe_gen_wa_oob.c
>index 6581cb0f0e59..0a94a045bcea 100644
>--- a/drivers/gpu/drm/xe/xe_gen_wa_oob.c
>+++ b/drivers/gpu/drm/xe/xe_gen_wa_oob.c
>@@ -125,9 +125,11 @@ static int parse(FILE *input, FILE *csource, FILE *cheader, char *prefix)
>
> static int fn_to_prefix(const char *fn, char *prefix, size_t size)
> {
>+	const char *base;
> 	size_t len;
>
>-	fn = basename(fn);
>+	base = strrchr(fn, '/');
>+	fn = base ? base + 1 : fn;

I think just a xbasename() helper like we've added in kmod would be
preferred:
https://github.com/kmod-project/kmod/commit/11eb9bc67c319900ab00523997323a97d2d08ad2

Alternativelly add it somewhere that can be shared across the userspace
tools in the kernel tree to fix the mess that we have here:

	git grep basename -- tools/**.c

Some dup the arg simply to be able to use the libgen.h version, some use
one or the other on purpose, etc etc.

Lucas De Marchi