From 1e423bff959e48166f5b7efca01fdb0dbdf05846 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 28 Jan 2016 15:11:28 -0800 Subject: x86/entry/64: Migrate the 64-bit syscall slow path to C This is more complicated than the 32-bit and compat cases because it preserves an asm fast path for the case where the callee-saved regs aren't needed in pt_regs and no entry or exit work needs to be done. This appears to slow down fastpath syscalls by no more than one cycle on my Skylake laptop. Signed-off-by: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/ce2335a4d42dc164b24132ee5e8c7716061f947b.1454022279.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/entry/common.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) (limited to 'arch/x86/entry/common.c') diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 03663740c866..75175f92f462 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -344,6 +344,32 @@ __visible inline void syscall_return_slowpath(struct pt_regs *regs) prepare_exit_to_usermode(regs); } +#ifdef CONFIG_X86_64 +__visible void do_syscall_64(struct pt_regs *regs) +{ + struct thread_info *ti = pt_regs_to_thread_info(regs); + unsigned long nr = regs->orig_ax; + + local_irq_enable(); + + if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) + nr = syscall_trace_enter(regs); + + /* + * NB: Native and x32 syscalls are dispatched from the same + * table. The only functional difference is the x32 bit in + * regs->orig_ax, which changes the behavior of some syscalls. + */ + if (likely((nr & __SYSCALL_MASK) < NR_syscalls)) { + regs->ax = sys_call_table[nr & __SYSCALL_MASK]( + regs->di, regs->si, regs->dx, + regs->r10, regs->r8, regs->r9); + } + + syscall_return_slowpath(regs); +} +#endif + #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) /* * Does a 32-bit syscall. Called with IRQs on and does all entry and -- cgit v1.2.3