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@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Pavel Machek <pavel@ucw.cz>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca>
Cc: joro@8bytes.org
Link: https://lkml.kernel.org/r/1531906876-13451-7-git-send-email-joro@8bytes.org

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 4364131..7251c4f 100644 (file)
--- 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