linux-kernel - [tip: x86/entry] x86/entry/64: Remove IRQ stack switching ASM

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Message-ID: <159056710606.17951.9824050639615238342.tip-bot2@tip-bot2>
Date:   Wed, 27 May 2020 08:11:46 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/entry] x86/entry/64: Remove IRQ stack switching ASM

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     300e5654198501a8cde5ad843ebad7dfbee147e4
Gitweb:        https://git.kernel.org/tip/300e5654198501a8cde5ad843ebad7dfbee147e4
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Thu, 21 May 2020 22:05:47 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 26 May 2020 19:06:29 +02:00

x86/entry/64: Remove IRQ stack switching ASM

No more users.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Acked-by: Andy Lutomirski <luto@...nel.org>
Link: https://lore.kernel.org/r/20200521202120.021462159@linutronix.de
---
 arch/x86/entry/entry_64.S | 96 +--------------------------------------
 1 file changed, 96 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 389f97f..29a8a83 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -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