Re: [PATCH v3 21/21] klp-build: Add arm64 syscall patching macro

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The arm64 __KLP_SYSCALL_DEFINEx macro omits the ALLOW_ERROR_INJECTION declaration, silently breaking BPF error injection for livepatched syscalls.
--

commit b4d1a9ea352f196a7fd3e7198fdade51440d08e5
Author: Josh Poimboeuf <jpoimboe@kernel.org>

klp-build: Add arm64 syscall patching macro

This commit adds arm64 support for KLP_SYSCALL_DEFINEx(). The commit
message states it is mirroring the arm64 __SYSCALL_DEFINEx() pattern from
arch/arm64/include/asm/syscall_wrapper.h.

> diff --git a/include/linux/livepatch_helpers.h b/include/linux/livepatch_helpers.h
> index 99d68d0773fa8..4b647b83865f9 100644
> --- a/include/linux/livepatch_helpers.h
> +++ b/include/linux/livepatch_helpers.h
> @@ -72,6 +72,25 @@
>  	}								\
>  	static inline long __klp_do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
>  
> +#elif defined(CONFIG_ARM64)
> +
> +#define __KLP_SYSCALL_DEFINEx(x, name, ...)				\
> +	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
> +	static inline long __klp_do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
> +	asmlinkage long __arm64_sys##name(const struct pt_regs *regs);	\
> +	asmlinkage long __arm64_sys##name(const struct pt_regs *regs)	\
> +	{								\
> +		return __se_sys##name(SC_ARM64_REGS_TO_ARGS(x,__VA_ARGS__));\
> +	}								\

Does this macro definition omit the ALLOW_ERROR_INJECTION declaration?

The standard arm64 __SYSCALL_DEFINEx() macro explicitly registers the top-level
syscall handler with ALLOW_ERROR_INJECTION() to enable BPF error injection
workflows like bpf_override_return(). The x86 implementation correctly
preserves this functionality.

Because this macro is missing that declaration, it looks like it might
introduce a regression where BPF cannot inject errors into the replacement
syscalls in a livepatch module on arm64.

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1778642120.git.jpoimboe@kernel.org?part=21