Commit e3e5c64e authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

x86/entry/64: Remove IRQ stack switching ASM 



No more users.

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/20200521202120.021462159@linutronix.de
parent 75da04f7

arch/x86/entry/entry_64.S

+0 −96
Original line number Diff line number Diff line
@@ -370,102 +370,6 @@ SYM_CODE_END(ret_from_fork) 
#endif

.endm



/*

 * Enters the IRQ stack if we're not already using it.  NMI-safe.  Clobbers

 * flags and puts old RSP into old_rsp, and leaves all other GPRs alone.

 * Requires kernel GSBASE.

 *

 * The invariant is that, if irq_count != -1, then the IRQ stack is in use.

 */

.macro ENTER_IRQ_STACK regs=1 old_rsp save_ret=0

	DEBUG_ENTRY_ASSERT_IRQS_OFF



	.if \save_ret

	/*

	 * If save_ret is set, the original stack contains one additional

	 * entry -- the return address. Therefore, move the address one

	 * entry below %rsp to \old_rsp.

	 */

	leaq	8(%rsp), \old_rsp

	.else

	movq	%rsp, \old_rsp

	.endif



	.if \regs

	UNWIND_HINT_REGS base=\old_rsp

	.endif



	incl	PER_CPU_VAR(irq_count)

	jnz	.Lirq_stack_push_old_rsp_\@



	/*

	 * Right now, if we just incremented irq_count to zero, we've

	 * claimed the IRQ stack but we haven't switched to it yet.

	 *

	 * If anything is added that can interrupt us here without using IST,

	 * it must be *extremely* careful to limit its stack usage.  This

	 * could include kprobes and a hypothetical future IST-less #DB

	 * handler.

	 *

	 * The OOPS unwinder relies on the word at the top of the IRQ

	 * stack linking back to the previous RSP for the entire time we're

	 * on the IRQ stack.  For this to work reliably, we need to write

	 * it before we actually move ourselves to the IRQ stack.

	 */



	movq	\old_rsp, PER_CPU_VAR(irq_stack_backing_store + IRQ_STACK_SIZE - 8)

	movq	PER_CPU_VAR(hardirq_stack_ptr), %rsp



#ifdef CONFIG_DEBUG_ENTRY

	/*

	 * If the first movq above becomes wrong due to IRQ stack layout

	 * changes, the only way we'll notice is if we try to unwind right

	 * here.  Assert that we set up the stack right to catch this type

	 * of bug quickly.

	 */

	cmpq	-8(%rsp), \old_rsp

	je	.Lirq_stack_okay\@

	ud2

	.Lirq_stack_okay\@:

#endif



.Lirq_stack_push_old_rsp_\@:

	pushq	\old_rsp



	.if \regs

	UNWIND_HINT_REGS indirect=1

	.endif



	.if \save_ret

	/*

	 * Push the return address to the stack. This return address can

	 * be found at the "real" original RSP, which was offset by 8 at

	 * the beginning of this macro.

	 */

	pushq	-8(\old_rsp)

	.endif

.endm



/*

 * Undoes ENTER_IRQ_STACK.

 */

.macro LEAVE_IRQ_STACK regs=1

	DEBUG_ENTRY_ASSERT_IRQS_OFF

	/* We need to be off the IRQ stack before decrementing irq_count. */

	popq	%rsp



	.if \regs

	UNWIND_HINT_REGS

	.endif



	/*

	 * As in ENTER_IRQ_STACK, irq_count == 0, we are still claiming

	 * the irq stack but we're not on it.

	 */



	decl	PER_CPU_VAR(irq_count)

.endm



/**

 * idtentry_body - Macro to emit code calling the C function

 * @cfunc:		C function to be called