Re: [PATCH v7 04/13] arm: Use the common syscall table

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] arm: OABI ABI breakage for epoll_pwait2 due to missing local syscall.tbl entry
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commit 538cbce7faef9329b4e409f09b73e772fc2b26c9
Author: André Almeida <andrealmeid@igalia.com>

arm: Use the common syscall table

Remove some of the duplicated code by using the common syscall number
table.

> diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
> index 55717ed32c27e..bccded328911a 100644
> --- a/arch/arm/tools/syscall.tbl
> +++ b/arch/arm/tools/syscall.tbl
> @@ -438,52 +438,3 @@
>  421	common	rt_sigtimedwait_time64		sys_rt_sigtimedwait
>  422	common	futex_time64			sys_futex
>  423	common	sched_rr_get_interval_time64	sys_sched_rr_get_interval
[ ... ]
> -440	common	process_madvise			sys_process_madvise
> -441	common	epoll_pwait2			sys_epoll_pwait2
> -442	common	mount_setattr			sys_mount_setattr

[Severity: High]
Does removing this local entry for epoll_pwait2 break OABI binaries?

By removing this entry, the build falls back to the common table definition
in scripts/syscall_common.tbl, which defines a compat handler:

441	common	epoll_pwait2		sys_epoll_pwait2	compat_sys_epoll_pwait2

OABI prefers the compat entry point when available, as mapped in
arch/arm/kernel/entry-common.S:

#undef __SYSCALL_WITH_COMPAT
#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)

This causes OABI to attempt to link compat_sys_epoll_pwait2 instead of the
native sys_epoll_pwait2 handler.

Because ARM32 lacks CONFIG_COMPAT, the weak stub in kernel/sys_ni.c resolves
the missing syscall to sys_ni_syscall:

COND_SYSCALL_COMPAT(epoll_pwait2);

Could this mask the build error while causing the syscall to silently fail at
runtime with -ENOSYS for any unprivileged OABI process calling epoll_pwait2?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260917-tonyk-syscall_table-v7-0-f4cd8f8e3265@igalia.com?part=4