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Commit 2140a994 authored by Jan Beulich's avatar Jan Beulich Committed by Ingo Molnar
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x86/entry/64: Relax pvops stub clobber specifications 



Except for the error_exit case, none of the code paths following the
{DIS,EN}ABLE_INTERRUPTS() invocations being modified here make any
assumptions on register values, so all registers can be clobbered
there. In the error_exit case a minor adjustment to register usage
(at once eliminating an instruction) also allows for this to be true.

Signed-off-by: default avatarJan Beulich <jbeulich@suse.com>
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: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/5894556D02000078001366D3@prv-mh.provo.novell.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent fdbd518a

arch/x86/entry/entry_64.S

+7 −8
Original line number Diff line number Diff line
@@ -212,7 +212,7 @@ entry_SYSCALL_64_fastpath: 
	 * If we see that no exit work is required (which we are required

	 * to check with IRQs off), then we can go straight to SYSRET64.

	 */

	DISABLE_INTERRUPTS(CLBR_NONE)

	DISABLE_INTERRUPTS(CLBR_ANY)

	TRACE_IRQS_OFF

	movq	PER_CPU_VAR(current_task), %r11

	testl	$_TIF_ALLWORK_MASK, TASK_TI_flags(%r11)
@@ -233,7 +233,7 @@ entry_SYSCALL_64_fastpath: 
	 * raise(3) will trigger this, for example.  IRQs are off.

	 */

	TRACE_IRQS_ON

	ENABLE_INTERRUPTS(CLBR_NONE)

	ENABLE_INTERRUPTS(CLBR_ANY)

	SAVE_EXTRA_REGS

	movq	%rsp, %rdi

	call	syscall_return_slowpath	/* returns with IRQs disabled */
@@ -343,7 +343,7 @@ ENTRY(stub_ptregs_64) 
	 * Called from fast path -- disable IRQs again, pop return address

	 * and jump to slow path

	 */

	DISABLE_INTERRUPTS(CLBR_NONE)

	DISABLE_INTERRUPTS(CLBR_ANY)

	TRACE_IRQS_OFF

	popq	%rax

	jmp	entry_SYSCALL64_slow_path
@@ -518,7 +518,7 @@ common_interrupt: 
	interrupt do_IRQ

	/* 0(%rsp): old RSP */

ret_from_intr:

	DISABLE_INTERRUPTS(CLBR_NONE)

	DISABLE_INTERRUPTS(CLBR_ANY)

	TRACE_IRQS_OFF

	decl	PER_CPU_VAR(irq_count)
@@ -1051,7 +1051,7 @@ END(paranoid_entry) 
 * On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it)

 */

ENTRY(paranoid_exit)

	DISABLE_INTERRUPTS(CLBR_NONE)

	DISABLE_INTERRUPTS(CLBR_ANY)

	TRACE_IRQS_OFF_DEBUG

	testl	%ebx, %ebx			/* swapgs needed? */

	jnz	paranoid_exit_no_swapgs
@@ -1156,10 +1156,9 @@ END(error_entry) 
 *   0: user gsbase is loaded, we need SWAPGS and standard preparation for return to usermode

 */

ENTRY(error_exit)

	movl	%ebx, %eax

	DISABLE_INTERRUPTS(CLBR_NONE)

	DISABLE_INTERRUPTS(CLBR_ANY)

	TRACE_IRQS_OFF

	testl	%eax, %eax

	testl	%ebx, %ebx

	jnz	retint_kernel

	jmp	retint_user

END(error_exit)