Commit fa95a0cb authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

x86/entry/32: Remove redundant irq disable code 



All exceptions/interrupts return with interrupts disabled now. No point in
doing this in ASM again.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarAndy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20200521202120.221223450@linutronix.de
parent 3b6c9bf6

arch/x86/entry/entry_32.S

+0 −76
Original line number Diff line number Diff line
@@ -51,34 +51,6 @@ 


	.section .entry.text, "ax"



/*

 * We use macros for low-level operations which need to be overridden

 * for paravirtualization.  The following will never clobber any registers:

 *   INTERRUPT_RETURN (aka. "iret")

 *   GET_CR0_INTO_EAX (aka. "movl %cr0, %eax")

 *   ENABLE_INTERRUPTS_SYSEXIT (aka "sti; sysexit").

 *

 * For DISABLE_INTERRUPTS/ENABLE_INTERRUPTS (aka "cli"/"sti"), you must

 * specify what registers can be overwritten (CLBR_NONE, CLBR_EAX/EDX/ECX/ANY).

 * Allowing a register to be clobbered can shrink the paravirt replacement

 * enough to patch inline, increasing performance.

 */



#ifdef CONFIG_PREEMPTION

# define preempt_stop(clobbers)	DISABLE_INTERRUPTS(clobbers); TRACE_IRQS_OFF

#else

# define preempt_stop(clobbers)

#endif



.macro TRACE_IRQS_IRET

#ifdef CONFIG_TRACE_IRQFLAGS

	testl	$X86_EFLAGS_IF, PT_EFLAGS(%esp)     # interrupts off?

	jz	1f

	TRACE_IRQS_ON

1:

#endif

.endm



#define PTI_SWITCH_MASK         (1 << PAGE_SHIFT)



/*
@@ -881,38 +853,6 @@ SYM_CODE_START(ret_from_fork) 
SYM_CODE_END(ret_from_fork)

.popsection



/*

 * Return to user mode is not as complex as all this looks,

 * but we want the default path for a system call return to

 * go as quickly as possible which is why some of this is

 * less clear than it otherwise should be.

 */



	# userspace resumption stub bypassing syscall exit tracing

SYM_CODE_START_LOCAL(ret_from_exception)

	preempt_stop(CLBR_ANY)

ret_from_intr:

#ifdef CONFIG_VM86

	movl	PT_EFLAGS(%esp), %eax		# mix EFLAGS and CS

	movb	PT_CS(%esp), %al

	andl	$(X86_EFLAGS_VM | SEGMENT_RPL_MASK), %eax

#else

	/*

	 * We can be coming here from child spawned by kernel_thread().

	 */

	movl	PT_CS(%esp), %eax

	andl	$SEGMENT_RPL_MASK, %eax

#endif

	cmpl	$USER_RPL, %eax

	jb	restore_all_kernel		# not returning to v8086 or userspace



	DISABLE_INTERRUPTS(CLBR_ANY)

	TRACE_IRQS_OFF

	movl	%esp, %eax

	call	prepare_exit_to_usermode

	jmp	restore_all_switch_stack

SYM_CODE_END(ret_from_exception)



SYM_ENTRY(__begin_SYSENTER_singlestep_region, SYM_L_GLOBAL, SYM_A_NONE)

/*

 * All code from here through __end_SYSENTER_singlestep_region is subject
@@ -1147,22 +1087,6 @@ restore_all_switch_stack: 
	 */

	INTERRUPT_RETURN



restore_all_kernel:

#ifdef CONFIG_PREEMPTION

	DISABLE_INTERRUPTS(CLBR_ANY)

	cmpl	$0, PER_CPU_VAR(__preempt_count)

	jnz	.Lno_preempt

	testl	$X86_EFLAGS_IF, PT_EFLAGS(%esp)	# interrupts off (exception path) ?

	jz	.Lno_preempt

	call	preempt_schedule_irq

.Lno_preempt:

#endif

	TRACE_IRQS_IRET

	PARANOID_EXIT_TO_KERNEL_MODE

	BUG_IF_WRONG_CR3

	RESTORE_REGS 4

	jmp	.Lirq_return



.section .fixup, "ax"

SYM_CODE_START(asm_iret_error)

	pushl	$0				# no error code