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x86/syscalls: Don't pointlessly reload the system call number

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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>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180405095307.3730-2-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Linus Torvalds 2018-04-05 11:53:00 +02:00 committed by Ingo Molnar
parent 642e7fd233
commit dfe64506c0
2 changed files with 8 additions and 7 deletions
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12
arch/x86/entry/common.c
View File

@ -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);

3
arch/x86/entry/entry_64.S
View File

@ -233,7 +233,8 @@ 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 */