linux-kernel - [PATCH 2/3] slab: convert setup_slub_debug() to use __core_param

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Message-ID: <9674b34861394088c7853edf8e9d2b439fd4b42f.1761324765.git.ptesarik@suse.com>
Date: Fri, 24 Oct 2025 19:06:53 +0200
From: Petr Tesarik <ptesarik@...e.com>
To: Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...two.org>,
	David Rientjes <rientjes@...gle.com>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Harry Yoo <harry.yoo@...cle.com>
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Petr Tesarik <ptesarik@...e.com>
Subject: [PATCH 2/3] slab: convert setup_slub_debug() to use __core_param_cb()

Use __core_param_cb() to parse the "slab_debug" kernel parameter instead of
the obsolescent __setup(). For now, the parameter is not exposed in sysfs,
and no get ops is provided.

There is a slight change in behavior. Before this patch, the following
parameter would silently turn on full debugging for all slabs:

  slub_debug_yada_yada_gotta_love_this=hail_satan!

This syntax is now rejected, and the parameter will be passed to user
space, making the kernel a holier place.

Signed-off-by: Petr Tesarik <ptesarik@...e.com>
---
 mm/slub.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 26faebcf27a2b..b124087b95f32 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1863,7 +1863,7 @@ parse_slub_debug_flags(const char *str, slab_flags_t *flags, const char **slabs,
 		return NULL;
 }
 
-static int __init setup_slub_debug(char *val)
+static int __init setup_slub_debug(const char *str, const struct kernel_param *kp)
 {
 	slab_flags_t flags;
 	slab_flags_t global_flags;
@@ -1871,10 +1871,9 @@ static int __init setup_slub_debug(char *val)
 	const char *slab_list;
 	bool global_slub_debug_changed = false;
 	bool slab_list_specified = false;
-	const char *str = val;
 
 	global_flags = DEBUG_DEFAULT_FLAGS;
-	if (*str++ != '=' || !*str)
+	if (!str || !*str)
 		/*
 		 * No options specified. Switch on full debugging.
 		 */
@@ -1918,11 +1917,15 @@ static int __init setup_slub_debug(char *val)
 	     static_branch_unlikely(&init_on_free)) &&
 	    (slub_debug & SLAB_POISON))
 		pr_info("mem auto-init: SLAB_POISON will take precedence over init_on_alloc/init_on_free\n");
-	return 1;
+	return 0;
 }
 
-__setup("slab_debug", setup_slub_debug);
-__setup_param("slub_debug", slub_debug, setup_slub_debug, 0);
+static const struct kernel_param_ops param_ops_slab_debug __initconst = {
+	.flags = KERNEL_PARAM_OPS_FL_NOARG,
+	.set = setup_slub_debug,
+};
+__core_param_cb(slab_debug, &param_ops_slab_debug, NULL, 0);
+__core_param_cb(slub_debug, &param_ops_slab_debug, NULL, 0);
 
 /*
  * kmem_cache_flags - apply debugging options to the cache
-- 
2.51.0