linux-kernel - [tip:x86/pti] x86/entry/32: Split off return-to-kernel path

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Date:   Thu, 19 Jul 2018 16:21:30 -0700
From:   tip-bot for Joerg Roedel <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     dave.hansen@...el.com, linux-kernel@...r.kernel.org,
        peterz@...radead.org, eduval@...zon.com, bp@...en8.de,
        mingo@...nel.org, tglx@...utronix.de, dvlasenk@...hat.com,
        jpoimboe@...hat.com, torvalds@...ux-foundation.org, hpa@...or.com,
        will.deacon@....com, aarcange@...hat.com, llong@...hat.com,
        jgross@...e.com, David.Laight@...lab.com,
        dhgutteridge@...patico.ca, jroedel@...e.de,
        gregkh@...uxfoundation.org, brgerst@...il.com, jkosina@...e.cz,
        luto@...nel.org, pavel@....cz, boris.ostrovsky@...cle.com
Subject: [tip:x86/pti] x86/entry/32: Split off return-to-kernel path

Commit-ID:  0d2eb73b29996684d5bbb72f85c74b47b4c359f7
Gitweb:     https://git.kernel.org/tip/0d2eb73b29996684d5bbb72f85c74b47b4c359f7
Author:     Joerg Roedel <jroedel@...e.de>
AuthorDate: Wed, 18 Jul 2018 11:40:43 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 20 Jul 2018 01:11:37 +0200

x86/entry/32: Split off return-to-kernel path

Use a separate return path when returning to the kernel.

This allows to put the PTI cr3-switch and the switch to the entry-stack
into the return-to-user path without further checking.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Pavel Machek <pavel@....cz>
Cc: "H . Peter Anvin" <hpa@...or.com>
Cc: linux-mm@...ck.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Brian Gerst <brgerst@...il.com>
Cc: David Laight <David.Laight@...lab.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Eduardo Valentin <eduval@...zon.com>
Cc: Greg KH <gregkh@...uxfoundation.org>
Cc: Will Deacon <will.deacon@....com>
Cc: aliguori@...zon.com
Cc: daniel.gruss@...k.tugraz.at
Cc: hughd@...gle.com
Cc: keescook@...gle.com
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Waiman Long <llong@...hat.com>
Cc: "David H . Gutteridge" <dhgutteridge@...patico.ca>
Cc: joro@...tes.org
Link: https://lkml.kernel.org/r/1531906876-13451-7-git-send-email-joro@8bytes.org

---
 arch/x86/entry/entry_32.S | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 43641310b6e3..7251c4f3e99e 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -65,7 +65,7 @@
 # define preempt_stop(clobbers)	DISABLE_INTERRUPTS(clobbers); TRACE_IRQS_OFF
 #else
 # define preempt_stop(clobbers)
-# define resume_kernel		restore_all
+# define resume_kernel		restore_all_kernel
 #endif

 .macro TRACE_IRQS_IRET
@@ -399,9 +399,9 @@ ENTRY(resume_kernel)
 	DISABLE_INTERRUPTS(CLBR_ANY)
 .Lneed_resched:
 	cmpl	$0, PER_CPU_VAR(__preempt_count)
-	jnz	restore_all
+	jnz	restore_all_kernel
 	testl	$X86_EFLAGS_IF, PT_EFLAGS(%esp)	# interrupts off (exception path) ?
-	jz	restore_all
+	jz	restore_all_kernel
 	call	preempt_schedule_irq
 	jmp	.Lneed_resched
 END(resume_kernel)
@@ -606,6 +606,11 @@ restore_all:
 	 */
 	INTERRUPT_RETURN

+restore_all_kernel:
+	TRACE_IRQS_IRET
+	RESTORE_REGS 4
+	jmp	.Lirq_return
+
 .section .fixup, "ax"
 ENTRY(iret_exc	)
 	pushl	$0				# no error code