x86/entry/64: Don't compile ignore_sysret if 32-bit emulation is enabled

It's only used if !CONFIG_IA32_EMULATION, so disable it in normal
configs.  This will save a few bytes of text and reduce confusion.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc:  "BaeChang Seok" <chang.seok.bae@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Bae, Chang Seok" <chang.seok.bae@intel.com>
Link: https://lkml.kernel.org/r/0f7dafa72fe7194689de5ee8cfe5d83509fabcf5.1562035429.git.luto@kernel.org

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 7f9f511..54b1b04 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1743,11 +1743,17 @@ nmi_restore:
        iretq
 END(nmi)
 
+#ifndef CONFIG_IA32_EMULATION
+/*
+ * This handles SYSCALL from 32-bit code.  There is no way to program
+ * MSRs to fully disable 32-bit SYSCALL.
+ */
 ENTRY(ignore_sysret)
        UNWIND_HINT_EMPTY
        mov     $-ENOSYS, %eax
        sysret
 END(ignore_sysret)
+#endif
 
 ENTRY(rewind_stack_do_exit)
        UNWIND_HINT_FUNC