linux-kernel - Re: [PATCH v4 13/18] kasan: arm64: x86: Handle int3 for inline KASAN reports

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Message-ID: <20250813151702.GO4067720@noisy.programming.kicks-ass.net>
Date: Wed, 13 Aug 2025 17:17:02 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
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Subject: Re: [PATCH v4 13/18] kasan: arm64: x86: Handle int3 for inline KASAN
 reports

On Tue, Aug 12, 2025 at 03:23:49PM +0200, Maciej Wieczor-Retman wrote:
> Inline KASAN on x86 does tag mismatch reports by passing the faulty
> address and metadata through the INT3 instruction - scheme that's setup
> in the LLVM's compiler code (specifically HWAddressSanitizer.cpp).
> 
> Add a kasan hook to the INT3 handling function.
> 
> Disable KASAN in an INT3 core kernel selftest function since it can raise
> a false tag mismatch report and potentially panic the kernel.
> 
> Make part of that hook - which decides whether to die or recover from a
> tag mismatch - arch independent to avoid duplicating a long comment on
> both x86 and arm64 architectures.
> 
> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>

Can we please split this into an arm64 and x86 patch. Also, why use int3
here rather than a #UD trap, which we use for all other such cases?