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Commit b7765086 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/entry/64: Fix an IRQ state error on ptregs-using syscalls 



I messed up the IRQ state when jumping off the fast path due to
invocation of a ptregs-using syscall.  This bug shouldn't have
had any impact yet, but it would have caused problems with
subsequent context tracking cleanups.

Reported-and-tested-by: default avatarBorislav Petkov <bp@suse.de>
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>
Fixes: 1e423bff x86/entry/64: ("Migrate the 64-bit syscall slow path to C")
Link: http://lkml.kernel.org/r/ab92cd365fb7b0a56869e920017790d96610fdca.1454261517.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 8c725306

arch/x86/entry/entry_64.S

+13 −6
Original line number Diff line number Diff line
@@ -191,8 +191,8 @@ entry_SYSCALL_64_fastpath: 


	/*

	 * This call instruction is handled specially in stub_ptregs_64.

	 * It might end up jumping to the slow path.  If it jumps, RAX is

	 * clobbered.

	 * It might end up jumping to the slow path.  If it jumps, RAX

	 * and all argument registers are clobbered.

	 */

	call	*sys_call_table(, %rax, 8)

.Lentry_SYSCALL_64_after_fastpath_call:
@@ -315,17 +315,24 @@ END(entry_SYSCALL_64) 
ENTRY(stub_ptregs_64)

	/*

	 * Syscalls marked as needing ptregs land here.

	 * If we are on the fast path, we need to save the extra regs.

	 * If we are on the slow path, the extra regs are already saved.

	 * If we are on the fast path, we need to save the extra regs,

	 * which we achieve by trying again on the slow path.  If we are on

	 * the slow path, the extra regs are already saved.

	 *

	 * RAX stores a pointer to the C function implementing the syscall.

	 * IRQs are on.

	 */

	cmpq	$.Lentry_SYSCALL_64_after_fastpath_call, (%rsp)

	jne	1f



	/* Called from fast path -- pop return address and jump to slow path */

	/*

	 * Called from fast path -- disable IRQs again, pop return address

	 * and jump to slow path

	 */

	DISABLE_INTERRUPTS(CLBR_NONE)

	TRACE_IRQS_OFF

	popq	%rax

	jmp	entry_SYSCALL64_slow_path	/* called from fast path */

	jmp	entry_SYSCALL64_slow_path



1:

	/* Called from C */