x86/entry/64: Remove the restore_c_regs_and_iret label

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>

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 5557e94c5f1c13201e2a8988a2cae9cbf921c992..33eb2127eac8bf8cf9da0d13926c1088c5b33303 100644 (file)
--- 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