From 3621644dbcd549dd5b7759d4eb25943699aa3c62 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 26 Feb 2018 19:20:13 -0800
Subject: [PATCH] x86: don't pointlessly reload the system call number
We have it in a register in the low-level asm, just pass it in as an
argument rather than have do_syscall_64() load it back in from the
ptregs pointer.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
arch/x86/entry/common.c | 12 ++++++------
arch/x86/entry/entry_64.S | 3 ++-
2 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 74f6eee15179..a8b066dbbf48 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -266,14 +266,13 @@ __visible inline void syscall_return_slowpath(struct pt_regs *regs)
}
#ifdef CONFIG_X86_64
-__visible void do_syscall_64(struct pt_regs *regs)
+__visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
{
- struct thread_info *ti = current_thread_info();
- unsigned long nr = regs->orig_ax;
+ struct thread_info *ti;
enter_from_user_mode();
local_irq_enable();
-
+ ti = current_thread_info();
if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY)
nr = syscall_trace_enter(regs);
@@ -282,8 +281,9 @@ __visible void do_syscall_64(struct pt_regs *regs)
* 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)) {
- nr = array_index_nospec(nr & __SYSCALL_MASK, NR_syscalls);
+ nr &= __SYSCALL_MASK;
+ if (likely(nr < NR_syscalls)) {
+ nr = array_index_nospec(nr, NR_syscalls);
regs->ax = sys_call_table[nr](
regs->di, regs->si, regs->dx,
regs->r10, regs->r8, regs->r9);
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 81d1a9f04e40..f731fd931d3d 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -184,7 +184,8 @@ GLOBAL(entry_SYSCALL_64_after_hwframe)
TRACE_IRQS_OFF
/* IRQs are off. */
- movq %rsp, %rdi
+ movq %rax, %rdi
+ movq %rsp, %rsi
call do_syscall_64 /* returns with IRQs disabled */
TRACE_IRQS_IRETQ /* we're about to change IF */
--
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