Do not use memcpy() to extract syscall arguments from struct pt_regs but rather just perform direct assignments. Update syscall_set_arguments() too to keep syscall_get_arguments() and syscall_set_arguments() in sync. With Generic Entry patch[1] and turn on audit, the performance benchmarks from perf bench basic syscall on kunpeng920 gives roughly a 1% performance uplift. | Metric | W/O this patch | With this patch | Change | | ---------- | -------------- | --------------- | --------- | | Total time | 2.241 [sec] | 2.211 [sec] | ↓1.36% | | usecs/op | 0.224157 | 0.221146 | ↓1.36% | | ops/sec | 4,461,157 | 4,501,409 | ↑0.9% | Disassembly shows that using direct assignment causes syscall_set_arguments() to be inlined and cuts the instruction count by five or six compared to memcpy(). Because __audit_syscall_entry() only uses four syscall arguments, the compiler has also elided the copy of regs->regs[4] and regs->regs[5]. Before: <syscall_get_arguments.constprop.0>: aa0103e2 mov x2, x1 91002003 add x3, x0, #0x8 f9408804 ldr x4, [x0, #272] f8008444 str x4, [x2], #8 a9409404 ldp x4, x5, [x0, #8] a9009424 stp x4, x5, [x1, #8] a9418400 ldp x0, x1, [x0, #24] a9010440 stp x0, x1, [x2, #16] f9401060 ldr x0, [x3, #32] f9001040 str x0, [x2, #32] d65f03c0 ret d503201f nop After: a9408e82 ldp x2, x3, [x20, #8] 2a1603e0 mov w0, w22 f9400e84 ldr x4, [x20, #24] f9408a81 ldr x1, [x20, #272] 9401c4ba bl ffff800080215ca8 <__audit_syscall_entry> This also aligns the implementation with x86 and RISC-V. [1]: https://lore.kernel.org/all/20251126071446.3234218-1-ruanjinjie@huawei.com/ Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> --- v2: - Also update syscall_set_arguments(). - Udpate the commit message. --- arch/arm64/include/asm/syscall.h | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h index f3853047c28e..5e4c7fc44f73 100644 --- a/arch/arm64/include/asm/syscall.h +++ b/arch/arm64/include/asm/syscall.h @@ -82,16 +82,24 @@ static inline void syscall_get_arguments(struct task_struct *task, unsigned long *args) { args[0] = regs->orig_x0; - args++; - - memcpy(args, ®s->regs[1], 5 * sizeof(args[0])); + args[1] = regs->regs[1]; + args[2] = regs->regs[2]; + args[3] = regs->regs[3]; + args[4] = regs->regs[4]; + args[5] = regs->regs[5]; } static inline void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs, const unsigned long *args) { - memcpy(®s->regs[0], args, 6 * sizeof(args[0])); + regs->regs[0] = args[0]; + regs->regs[1] = args[1]; + regs->regs[2] = args[2]; + regs->regs[3] = args[3]; + regs->regs[4] = args[4]; + regs->regs[5] = args[5]; + /* * Also copy the first argument into orig_x0 * so that syscall_get_arguments() would return it -- 2.34.1