linux-kernel - [PATCH v3 03/12] kasan/powerpc: select ARCH_DEFER_KASAN and call kasan_init

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Message-Id: <20250717142732.292822-4-snovitoll@gmail.com>
Date: Thu, 17 Jul 2025 19:27:23 +0500
From: Sabyrzhan Tasbolatov <snovitoll@...il.com>
To: hca@...ux.ibm.com,
	christophe.leroy@...roup.eu,
	andreyknvl@...il.com,
	agordeev@...ux.ibm.com,
	akpm@...ux-foundation.org
Cc: ryabinin.a.a@...il.com,
	glider@...gle.com,
	dvyukov@...gle.com,
	kasan-dev@...glegroups.com,
	linux-kernel@...r.kernel.org,
	loongarch@...ts.linux.dev,
	linuxppc-dev@...ts.ozlabs.org,
	linux-riscv@...ts.infradead.org,
	linux-s390@...r.kernel.org,
	linux-um@...ts.infradead.org,
	linux-mm@...ck.org,
	snovitoll@...il.com
Subject: [PATCH v3 03/12] kasan/powerpc: select ARCH_DEFER_KASAN and call kasan_init_generic

PowerPC with radix MMU is the primary architecture that needs deferred
KASAN initialization, as it requires complex shadow memory setup before
KASAN can be safely enabled.

Select ARCH_DEFER_KASAN for PPC_RADIX_MMU to enable the static key
mechanism for runtime KASAN control. Other PowerPC configurations
(like book3e and 32-bit) can enable KASAN early and will use
compile-time constants instead.

Also call kasan_init_generic() which handles Generic KASAN initialization.
For PowerPC radix MMU (which selects ARCH_DEFER_KASAN), this enables
the static key. For other PowerPC variants, kasan_enable() is a no-op
and kasan_enabled() returns IS_ENABLED(CONFIG_KASAN).

Remove the PowerPC-specific static key and kasan_arch_is_ready()
implementation in favor of the unified interface.

This ensures that:
- PowerPC radix gets the runtime control it needs
- Other PowerPC variants get optimal compile-time behavior
- No unnecessary overhead is added where not needed

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217049
Fixes: 55d77bae7342 ("kasan: fix Oops due to missing calls to kasan_arch_is_ready()")
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@...il.com>
---
Changes in v3:
- Added CONFIG_ARCH_DEFER_KASAN selection for PPC_RADIX_MMU only
- Kept ARCH_DISABLE_KASAN_INLINE selection since it's needed independently
---
 arch/powerpc/Kconfig                   |  1 +
 arch/powerpc/include/asm/kasan.h       | 12 ------------
 arch/powerpc/mm/kasan/init_32.c        |  2 +-
 arch/powerpc/mm/kasan/init_book3e_64.c |  2 +-
 arch/powerpc/mm/kasan/init_book3s_64.c |  6 +-----
 5 files changed, 4 insertions(+), 19 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index c3e0cc83f12..e5a6aae6a77 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -123,6 +123,7 @@ config PPC
 	#
 	select ARCH_32BIT_OFF_T if PPC32
 	select ARCH_DISABLE_KASAN_INLINE	if PPC_RADIX_MMU
+	select ARCH_DEFER_KASAN			if PPC_RADIX_MMU
 	select ARCH_DMA_DEFAULT_COHERENT	if !NOT_COHERENT_CACHE
 	select ARCH_ENABLE_MEMORY_HOTPLUG
 	select ARCH_ENABLE_MEMORY_HOTREMOVE
diff --git a/arch/powerpc/include/asm/kasan.h b/arch/powerpc/include/asm/kasan.h
index b5bbb94c51f..957a57c1db5 100644
--- a/arch/powerpc/include/asm/kasan.h
+++ b/arch/powerpc/include/asm/kasan.h
@@ -53,18 +53,6 @@
 #endif
 
 #ifdef CONFIG_KASAN
-#ifdef CONFIG_PPC_BOOK3S_64
-DECLARE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
-
-static __always_inline bool kasan_arch_is_ready(void)
-{
-	if (static_branch_likely(&powerpc_kasan_enabled_key))
-		return true;
-	return false;
-}
-
-#define kasan_arch_is_ready kasan_arch_is_ready
-#endif
 
 void kasan_early_init(void);
 void kasan_mmu_init(void);
diff --git a/arch/powerpc/mm/kasan/init_32.c b/arch/powerpc/mm/kasan/init_32.c
index 03666d790a5..1d083597464 100644
--- a/arch/powerpc/mm/kasan/init_32.c
+++ b/arch/powerpc/mm/kasan/init_32.c
@@ -165,7 +165,7 @@ void __init kasan_init(void)
 
 	/* At this point kasan is fully initialized. Enable error messages */
 	init_task.kasan_depth = 0;
-	pr_info("KASAN init done\n");
+	kasan_init_generic();
 }
 
 void __init kasan_late_init(void)
diff --git a/arch/powerpc/mm/kasan/init_book3e_64.c b/arch/powerpc/mm/kasan/init_book3e_64.c
index 60c78aac0f6..0d3a73d6d4b 100644
--- a/arch/powerpc/mm/kasan/init_book3e_64.c
+++ b/arch/powerpc/mm/kasan/init_book3e_64.c
@@ -127,7 +127,7 @@ void __init kasan_init(void)
 
 	/* Enable error messages */
 	init_task.kasan_depth = 0;
-	pr_info("KASAN init done\n");
+	kasan_init_generic();
 }
 
 void __init kasan_late_init(void) { }
diff --git a/arch/powerpc/mm/kasan/init_book3s_64.c b/arch/powerpc/mm/kasan/init_book3s_64.c
index 7d959544c07..dcafa641804 100644
--- a/arch/powerpc/mm/kasan/init_book3s_64.c
+++ b/arch/powerpc/mm/kasan/init_book3s_64.c
@@ -19,8 +19,6 @@
 #include <linux/memblock.h>
 #include <asm/pgalloc.h>
 
-DEFINE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
-
 static void __init kasan_init_phys_region(void *start, void *end)
 {
 	unsigned long k_start, k_end, k_cur;
@@ -92,11 +90,9 @@ void __init kasan_init(void)
 	 */
 	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
 
-	static_branch_inc(&powerpc_kasan_enabled_key);
-
 	/* Enable error messages */
 	init_task.kasan_depth = 0;
-	pr_info("KASAN init done\n");
+	kasan_init_generic();
 }
 
 void __init kasan_early_init(void) { }
-- 
2.34.1