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

[Josh Poimboeuf]

On Fri, May 15, 2026 at 02:44:39AM +0000, sashiko-bot at kernel.org wrote:
> 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 at 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.

Fixed.

-- 
Josh