Re: [PATCH v2 2/2] arm64: hibernate: use a typed entry to drop __nocfi

[sashiko-bot@kernel.org]

> swsusp_arch_resume() calls the safe page's copy of
> swsusp_arch_suspend_exit() indirectly, without a kCFI check. The MMU is
> on at the call and TTBR0 maps only that page. The copy starts at the
> page's first byte, so the check's load of the type hash in front of it
> would fault. SYM_CODE_START() also gives the routine no hash.
> Commit e2f8216ca2d8 ("arm64: Set __nocfi on swsusp_arch_resume()")
> disabled the check "for now", since the entry had to be first
> in .hibernate_exit.text.
> 
> SYM_TYPED_FUNC_START() emits the hash inside that section, and
> create_safe_exec_page() already copies the whole section, at most 4 KiB,
> to the page's start, so the page holds both hash and entry. Relax the
> linker script's ASSERT, so the entry need only be in the section.
> 
> Fix by typing the routine, with a C prototype, entering the copy at the
> symbol's offset in the section, and dropping __nocfi.
> 
> Suggested-by: Mark Rutland <mark.rutland@arm.com>
> Link: https://lore.kernel.org/linux-arm-kernel/arZSe8hNnRPM5FqY@J2N7QTR9R3.cambridge.arm.com/
> Signed-off-by: Ben Cressey <ben@cressey.dev>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261111-arm64-kexec-nocfi-v2-0-ddf0c4aa326f@cressey.dev?part=2