x86/entry/64: Split the IRET-to-user and IRET-to-kernel paths

These code paths will diverge soon.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
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/dccf8c7b3750199b4b30383c812d4e2931811509.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index e8ef83d..3eeb169 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -321,7 +321,7 @@ syscall_return_via_sysret:
 
 opportunistic_sysret_failed:
        SWAPGS
-       jmp     restore_regs_and_iret
+       jmp     restore_regs_and_return_to_usermode
 END(entry_SYSCALL_64)
 
 ENTRY(stub_ptregs_64)
@@ -423,7 +423,7 @@ ENTRY(ret_from_fork)
        call    syscall_return_slowpath /* returns with IRQs disabled */
        TRACE_IRQS_ON                   /* user mode is traced as IRQS on */
        SWAPGS
-       jmp     restore_regs_and_iret
+       jmp     restore_regs_and_return_to_usermode
 
 1:
        /* kernel thread */
@@ -612,7 +612,20 @@ GLOBAL(retint_user)
        call    prepare_exit_to_usermode
        TRACE_IRQS_IRETQ
        SWAPGS
-       jmp     restore_regs_and_iret
+
+GLOBAL(restore_regs_and_return_to_usermode)
+#ifdef CONFIG_DEBUG_ENTRY
+       /* Assert that pt_regs indicates user mode. */
+       testl   $3, CS(%rsp)
+       jnz     1f
+       ud2
+1:
+#endif
+       RESTORE_EXTRA_REGS
+       RESTORE_C_REGS
+       REMOVE_PT_GPREGS_FROM_STACK 8
+       INTERRUPT_RETURN
+
 
 /* Returning to kernel space */
 retint_kernel:
@@ -632,11 +645,14 @@ retint_kernel:
         */
        TRACE_IRQS_IRETQ
 
-/*
- * At this label, code paths which return to kernel and to user,
- * which come from interrupts/exception and from syscalls, merge.
- */
-GLOBAL(restore_regs_and_iret)
+GLOBAL(restore_regs_and_return_to_kernel)
+#ifdef CONFIG_DEBUG_ENTRY
+       /* Assert that pt_regs indicates kernel mode. */
+       testl   $3, CS(%rsp)
+       jz      1f
+       ud2
+1:
+#endif
        RESTORE_EXTRA_REGS
        RESTORE_C_REGS
        REMOVE_PT_GPREGS_FROM_STACK 8
@@ -1327,7 +1343,7 @@ ENTRY(nmi)
         * work, because we don't want to enable interrupts.
         */
        SWAPGS
-       jmp     restore_regs_and_iret
+       jmp     restore_regs_and_return_to_usermode
 
 .Lnmi_from_kernel:
        /*

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index e26c25c..9ca014a 100644 (file)
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -337,7 +337,7 @@ ENTRY(entry_INT80_compat)
        /* Go back to user mode. */
        TRACE_IRQS_ON
        SWAPGS
-       jmp     restore_regs_and_iret
+       jmp     restore_regs_and_return_to_usermode
 END(entry_INT80_compat)
 
 ENTRY(stub32_clone)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 189bf42..08f067f 100644 (file)
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -326,7 +326,7 @@ early_idt_handler_common:
 
 20:
        decl early_recursion_flag(%rip)
-       jmp restore_regs_and_iret
+       jmp restore_regs_and_return_to_kernel
 END(early_idt_handler_common)
 
        __INITDATA