Re: [patch 16/18] x86/entry: Get rid of the sys_ni_syscall() indirection
From: Jinjie Ruan <hidden>
Date: 2026-07-09 02:03:55
Also in:
linux-alpha, linux-arch, linux-doc, linux-m68k, linux-mips, linux-riscv, linux-s390, linux-sh, linux-um, lkml, loongarch, sparclinux
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 <redacted>
quoted hunk ↗ jump to hunk
Remove the extra conditionals and the function calls. Signed-off-by: Thomas Gleixner <tglx@kernel.org> --- 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);