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From: Nam Cao <namcao@linutronix.de>
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To: Kees Cook <kees@kernel.org>, Paul Walmsley <pjw@kernel.org>
Cc: Kees Cook <kees@kernel.org>, Palmer Dabbelt <palmer@dabbelt.com>, Albert
 Ou <aou@eecs.berkeley.edu>, Alexandre Ghiti <alex@ghiti.fr>, Andrew Jones
 <ajones@ventanamicro.com>, Conor Dooley <conor.dooley@microchip.com>,
 =?utf-8?Q?Cl=C3=A9ment_L=C3=A9ger?= <cleger@rivosinc.com>, Evan Green
 <evan@rivosinc.com>,
 linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
 linux-hardening@vger.kernel.org
Subject: Re: [PATCH] riscv: Add kCFI type prefix to unaligned copy routines
In-Reply-To: <20260618081252.work.711-kees@kernel.org>
References: <20260618081252.work.711-kees@kernel.org>
Date: Thu, 18 Jun 2026 12:10:00 +0200
Message-ID: <877bnwtb0n.fsf@yellow.woof>
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Kees Cook <kees@kernel.org> writes:
> __riscv_copy_words_unaligned() and __riscv_copy_bytes_unaligned() are
> called indirectly through function pointers from measure_cycles() (via
> compare_unaligned_access()) during the boot-time unaligned-access
> probe. Under kCFI, an indirect call checks the type id stored in the
> word immediately preceding the callee against the type id of the
> function-pointer type at the call site. These two routines are defined
> with SYM_FUNC_START(), which emits no __cfi_ prefix, so the check reads
> the alignment padding ahead of the function (zero) instead of a type id
> and traps:

This has already been fixed by commit f2abc305aa93f ("riscv: Define
__riscv_copy_{,vec_}{words,bytes}_unaligned() using SYM_TYPED_FUNC_START")

Nam