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[v3,09/14] x86: Minimal SLAB alignment

Message ID 173d99afea37321e76e9380b49bd5966be8db849.1743772053.git.maciej.wieczor-retman@intel.com (mailing list archive)
State New
Headers show
Series [v3,01/14] kasan: sw_tags: Use arithmetic shift for shadow computation | expand

Commit Message

Maciej Wieczor-Retman April 4, 2025, 1:14 p.m. UTC 
Adjust x86 minimal SLAB alignment to match KASAN granularity size. In
tag-based mode the size changes to 16 bytes so the value needs to be 16.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
---
Changelog v3:
- Fix typo in patch message 4 -> 16.
- Change define location to arch/x86/include/asm/cache.c.

 arch/x86/include/asm/cache.h | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Dave Hansen April 4, 2025, 4:59 p.m. UTC | #1 
On 4/4/25 06:14, Maciej Wieczor-Retman wrote:
> Adjust x86 minimal SLAB alignment to match KASAN granularity size. In
> tag-based mode the size changes to 16 bytes so the value needs to be 16.

I feel like we need a _bit_ of a discussion of the impact here. We are,
after all, trying to get this feature into shape so that it can be used
more widely outside of just debugging environments.

What's the impact of this in a production environment?
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Patch

diff --git a/arch/x86/include/asm/cache.h b/arch/x86/include/asm/cache.h
index 69404eae9983..3232583b5487 100644
--- a/arch/x86/include/asm/cache.h
+++ b/arch/x86/include/asm/cache.h
@@ -21,4 +21,8 @@ 
 #endif
 #endif
 
+#ifdef CONFIG_KASAN_SW_TAGS
+#define ARCH_SLAB_MINALIGN (1ULL << KASAN_SHADOW_SCALE_SHIFT)
+#endif
+
 #endif /* _ASM_X86_CACHE_H */