From: Maciej Wieczor-Retman <m.wieczorretman@pm.me>
To: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: corbet@lwn.net, morbo@google.com, rppt@kernel.org,
lorenzo.stoakes@oracle.com, ubizjak@gmail.com, mingo@redhat.com,
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Subject: Re: [PATCH v8 00/14] kasan: x86: arm64: KASAN tag-based mode for x86
Date: Mon, 19 Jan 2026 19:43:23 +0000 [thread overview]
Message-ID: <aW6HcGjkAZ3lITeA@wieczorr-mobl1.localdomain> (raw)
In-Reply-To: <e273571e-ab8f-46d6-a44e-c1d0d06d3cbf@gmail.com>
On 2026-01-19 at 17:33:35 +0100, Andrey Ryabinin wrote:
>On 1/12/26 6:26 PM, Maciej Wieczor-Retman wrote:
>
>> ======= Compilation
>> Clang was used to compile the series (make LLVM=1) since gcc doesn't
>> seem to have support for KASAN tag-based compiler instrumentation on
>> x86.
>>
>
>It appears that GCC nominally supports this, but in practice it does not work.
>Here is a minimal reproducer: https://godbolt.org/z/s85e11T5r
>
>As far as I understand, calling a function through a tagged pointer is not
>supported by the hardware, so GCC attempts to clear the tag before the call.
>This behavior seems to be inherited from the userspace implementation of HWASan (-fsanitize=hwaddress).
>
>I have filed a GCC bug report: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123696
>
>For the kernel, we probably do not want this masking at all, as effectively 99.9–100%
>of function pointer calls are expected to be untagged anyway.
>
>Clang does not appear to do this, not even for userspace.
Cool, thanks, nice to know why the kernel didn't start with gcc.
I'm going to check in on the bug report every now and then and once it gets
resolved I'll test if everything works as expected on both compilers.
--
Kind regards
Maciej Wieczór-Retman
prev parent reply other threads:[~2026-01-19 19:43 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-12 17:26 Maciej Wieczor-Retman
2026-01-12 17:27 ` [PATCH v8 01/14] kasan: sw_tags: Use arithmetic shift for shadow computation Maciej Wieczor-Retman
2026-01-15 22:42 ` Andrey Ryabinin
2026-01-16 13:11 ` Maciej Wieczor-Retman
2026-01-12 17:27 ` [PATCH v8 02/14] kasan: arm64: x86: Make special tags arch specific Maciej Wieczor-Retman
2026-01-13 1:21 ` Andrey Konovalov
2026-01-13 17:32 ` Maciej Wieczor-Retman
2026-01-16 13:32 ` Andrey Ryabinin
2026-01-12 17:27 ` [PATCH v8 04/14] x86/kasan: Add arch specific kasan functions Maciej Wieczor-Retman
2026-01-13 1:21 ` Andrey Konovalov
2026-01-13 16:12 ` Maciej Wieczor-Retman
2026-01-16 13:35 ` Andrey Ryabinin
2026-01-12 17:27 ` [PATCH v8 06/14] mm/execmem: Untag addresses in EXECMEM_ROX related pointer arithmetic Maciej Wieczor-Retman
2026-01-12 17:28 ` [PATCH v8 13/14] x86/kasan: Logical bit shift for kasan_mem_to_shadow Maciej Wieczor-Retman
2026-01-13 1:21 ` Andrey Konovalov
2026-01-14 16:52 ` Maciej Wieczor-Retman
2026-01-15 3:57 ` Andrey Konovalov
2026-01-15 16:43 ` Maciej Wieczor-Retman
2026-01-17 1:21 ` Andrey Konovalov
2026-01-17 6:53 ` Maciej Wieczór-Retman
2026-01-19 11:40 ` Maciej Wieczor-Retman
2026-01-12 18:29 ` [PATCH v8 00/14] kasan: x86: arm64: KASAN tag-based mode for x86 Andrew Morton
2026-01-12 20:08 ` Maciej Wieczór-Retman
2026-01-12 20:53 ` Andrew Morton
2026-01-13 1:47 ` Andrey Konovalov
2026-01-12 20:27 ` Dave Hansen
2026-01-13 11:47 ` Borislav Petkov
2026-01-13 17:34 ` Andrew Morton
2026-01-22 17:25 ` Maciej Wieczor-Retman
2026-01-13 1:44 ` Andrey Konovalov
2026-01-19 16:33 ` Andrey Ryabinin
2026-01-19 19:43 ` Maciej Wieczor-Retman [this message]
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