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Commit 8b13c255 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/entry: Remove unnecessary IRQ twiddling in fast 32-bit syscalls 



This is slightly messy, but it eliminates an unnecessary cli;sti
pair.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
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: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/22f34b1096694a37326f36c53407b8dd90f37948.1444091585.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 487e3bf4

arch/x86/entry/common.c

+11 −7
Original line number Diff line number Diff line
@@ -323,10 +323,10 @@ __visible void syscall_return_slowpath(struct pt_regs *regs) 


#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)

/*

 * Does a 32-bit syscall.  Called with IRQs off and does all entry and

 * exit work.

 * Does a 32-bit syscall.  Called with IRQs on and does all entry and

 * exit work and returns with IRQs off.

 */

__visible void do_int80_syscall_32(struct pt_regs *regs)

static void do_syscall_32_irqs_on(struct pt_regs *regs)

{

	struct thread_info *ti = pt_regs_to_thread_info(regs);

	unsigned int nr = (unsigned int)regs->orig_ax;
@@ -335,8 +335,6 @@ __visible void do_int80_syscall_32(struct pt_regs *regs) 
	ti->status |= TS_COMPAT;

#endif



	local_irq_enable();



	if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {

		/*

		 * Subtlety here: if ptrace pokes something larger than
@@ -363,6 +361,13 @@ __visible void do_int80_syscall_32(struct pt_regs *regs) 
	syscall_return_slowpath(regs);

}



/* Handles int $0x80 */

__visible void do_int80_syscall_32(struct pt_regs *regs)

{

	local_irq_enable();

	do_syscall_32_irqs_on(regs);

}



/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */

__visible long do_fast_syscall_32(struct pt_regs *regs)

{
@@ -398,10 +403,9 @@ __visible long do_fast_syscall_32(struct pt_regs *regs) 
		prepare_exit_to_usermode(regs);

		return 0;	/* Keep it simple: use IRET. */

	}

	local_irq_disable();



	/* Now this is just like a normal syscall. */

	do_int80_syscall_32(regs);

	do_syscall_32_irqs_on(regs);



#ifdef CONFIG_X86_64

	/*