[PATCH 4.14 035/159] x86/entry/64: Remove the restore_c_regs_and_iret label

Greg Kroah-Hartman
2017-12-22T08:59:48Z

From: Andy Lutomirski <luto@kernel.org>

commit 9da78ba6b47b46428cfdfc0851511ab29c869798 upstream.

The only user was the 64-bit opportunistic SYSRET failure path, and
that path didn't really need it. This change makes the
opportunistic SYSRET code a bit more straightforward and gets rid of
the label.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/be3006a7ad3326e3458cf1cc55d416252cbe1986.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/entry/entry_64.S | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -246,7 +246,6 @@ entry_SYSCALL64_slow_path:
call do_syscall_64 /* returns with IRQs disabled */

return_from_SYSCALL_64:
- RESTORE_EXTRA_REGS
TRACE_IRQS_IRETQ /* we're about to change IF */

/*
@@ -315,6 +314,7 @@ return_from_SYSCALL_64:
*/
syscall_return_via_sysret:
/* rcx and r11 are already restored (see code above) */
+ RESTORE_EXTRA_REGS
RESTORE_C_REGS_EXCEPT_RCX_R11
movq RSP(%rsp), %rsp
UNWIND_HINT_EMPTY
@@ -322,7 +322,7 @@ syscall_return_via_sysret:

opportunistic_sysret_failed:
SWAPGS
- jmp restore_c_regs_and_iret
+ jmp restore_regs_and_iret
END(entry_SYSCALL_64)

ENTRY(stub_ptregs_64)
@@ -639,7 +639,6 @@ retint_kernel:
*/
GLOBAL(restore_regs_and_iret)
RESTORE_EXTRA_REGS
-restore_c_regs_and_iret:
RESTORE_C_REGS
REMOVE_PT_GPREGS_FROM_STACK 8
INTERRUPT_RETURN