On 7/8/2026 3:07 AM, Thomas Gleixner wrote:
> Invoking sys_ni_syscall() from a code path, which already knows that the
> syscall number is invalid just to assign -ENOSYS to regs->ax is a pointless
> exercise. It's even redundant as the low level entry code already has set
> regs->ax to -ENOSYS on entry.
Makes sense, the all reltaed entry has already initialized
regs->ax to -ENOSYS.
This makes the code very concise.
LGTM
Reviewed-by: Jinjie Ruan <[email protected]>
>
> Remove the extra conditionals and the function calls.
>
> Signed-off-by: Thomas Gleixner <[email protected]>
> ---
> arch/x86/entry/syscall_32.c | 2 --
> arch/x86/entry/syscall_64.c | 10 +++-------
> 2 files changed, 3 insertions(+), 9 deletions(-)
>
> --- a/arch/x86/entry/syscall_32.c
> +++ b/arch/x86/entry/syscall_32.c
> @@ -81,8 +81,6 @@ static __always_inline void do_syscall_3
> if (likely(unr < IA32_NR_syscalls)) {
> unr = array_index_nospec(unr, IA32_NR_syscalls);
> regs->ax = ia32_sys_call(regs, unr);
> - } else if (nr != -1) {
> - regs->ax = __ia32_sys_ni_syscall(regs);
> }
> }
>
> --- a/arch/x86/entry/syscall_64.c
> +++ b/arch/x86/entry/syscall_64.c
> @@ -68,7 +68,7 @@ static __always_inline bool do_syscall_x
> return false;
> }
>
> -static __always_inline bool do_syscall_x32(struct pt_regs *regs, int nr)
> +static __always_inline void do_syscall_x32(struct pt_regs *regs, int nr)
> {
> /*
> * Adjust the starting offset of the table, and convert numbers
> @@ -80,9 +80,7 @@ static __always_inline bool do_syscall_x
> if (IS_ENABLED(CONFIG_X86_X32_ABI) && likely(xnr < X32_NR_syscalls)) {
> xnr = array_index_nospec(xnr, X32_NR_syscalls);
> regs->ax = x32_sys_call(regs, xnr);
> - return true;
> }
> - return false;
> }
>
> /* Returns true to return using SYSRET, or false to use IRET */
> @@ -92,10 +90,8 @@ static __always_inline bool do_syscall_x
>
> instrumentation_begin();
>
> - if (!do_syscall_x64(regs, nr) && !do_syscall_x32(regs, nr) && nr != -1)
> {
> - /* Invalid system call, but still a system call. */
> - regs->ax = __x64_sys_ni_syscall(regs);
> - }
> + if (!do_syscall_x64(regs, nr))
> + do_syscall_x32(regs, nr);
>
> instrumentation_end();
> syscall_exit_to_user_mode(regs);
>
