linux-kernel - [patch 02/15] x86/entry/64: Add ability to switch to IRQ stacks in idtentry

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Date:   Tue, 25 Feb 2020 23:47:21 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Steven Rostedt <rostedt@...dmis.org>,
        Brian Gerst <brgerst@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>
Subject: [patch 02/15] x86/entry/64: Add ability to switch to IRQ stacks in idtentry

Expand the idtentry macro so it supports switching to interrupt stacks on
64bit. Preparatory change to let regular device interrupts use idtentry
instead of having their own mechanism.

Suggested-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/entry/entry_64.S |   18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -495,8 +495,9 @@ SYM_CODE_END(spurious_entries_start)
  * idtentry_body - Macro to emit code calling the C function
  * @cfunc:		C function to be called
  * @has_error_code:	Hardware pushed error code on stack
+ * @irq_stack:		Execute @cfunc on the IRQ stack (device interrupts)
  */
-.macro idtentry_body cfunc has_error_code:req
+.macro idtentry_body cfunc has_error_code:req irq_stack:req
 
 	call	error_entry
 	UNWIND_HINT_REGS
@@ -508,8 +509,16 @@ SYM_CODE_END(spurious_entries_start)
 		movq	$-1, ORIG_RAX(%rsp)	/* no syscall to restart */
 	.endif
 
+	.if \irq_stack
+		ENTER_IRQ_STACK old_rsp=%rdi
+	.endif
+
 	call	\cfunc
 
+	.if \irq_stack
+		LEAVE_IRQ_STACK			/* interrupts are disabled */
+	.endif
+
 	jmp	error_exit
 .endm
 
@@ -519,11 +528,12 @@ SYM_CODE_END(spurious_entries_start)
  * @asmsym:		ASM symbol for the entry point
  * @cfunc:		C function to be called
  * @has_error_code:	Hardware pushed error code on stack
+ * @irq_stack:		Execute @cfunc on the IRQ stack (device interrupts)
  *
  * The macro emits code to set up the kernel context for straight forward
  * and simple IDT entries. No IST stack, no paranoid entry checks.
  */
-.macro idtentry vector asmsym cfunc has_error_code:req
+.macro idtentry vector asmsym cfunc has_error_code:req irq_stack=0
 SYM_CODE_START(\asmsym)
 	UNWIND_HINT_IRET_REGS offset=\has_error_code*8
 	ASM_CLAC
@@ -546,7 +556,7 @@ SYM_CODE_START(\asmsym)
 .Lfrom_usermode_no_gap_\@:
 	.endif
 
-	idtentry_body \cfunc \has_error_code
+	idtentry_body \cfunc \has_error_code \irq_stack
 
 _ASM_NOKPROBE(\asmsym)
 SYM_CODE_END(\asmsym)
@@ -621,7 +631,7 @@ SYM_CODE_START(\asmsym)
 
 	/* Switch to the regular task stack and use the noist entry point */
 .Lfrom_usermode_switch_stack_\@:
-	idtentry_body noist_\cfunc, has_error_code=0
+	idtentry_body noist_\cfunc, has_error_code=0 irq_stack=0
 
 _ASM_NOKPROBE(\asmsym)
 SYM_CODE_END(\asmsym)