x86/entry, locking/lockdep: Move lockdep_sys_exit() to prepare_exit_to_usermode()

Rather than worrying about exactly where LOCKDEP_SYS_EXIT should
go in the asm code, add it to prepare_exit_from_usermode() and
remove all of the asm calls that are followed by
prepare_exit_to_usermode().

LOCKDEP_SYS_EXIT now appears only in the syscall fast paths.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1736ebe948b845e68120b86b89091f3ec27f5e8e.1444091584.git.luto@kernel.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/entry/common.c

@@ -220,6 +220,8 @@ __visible void prepare_exit_to_usermode(struct pt_regs *regs)
 	if (WARN_ON(!irqs_disabled()))
 		local_irq_disable();
 
+	lockdep_sys_exit();
+
 	/*
 	 * In order to return to user mode, we need to have IRQs off with
 	 * none of _TIF_SIGPENDING, _TIF_NOTIFY_RESUME, _TIF_USER_RETURN_NOTIFY,

arch/x86/entry/entry_32.S

@@ -255,7 +255,6 @@ ret_from_intr:
 	jb	resume_kernel			# not returning to v8086 or userspace
 
 ENTRY(resume_userspace)
-	LOCKDEP_SYS_EXIT
 	DISABLE_INTERRUPTS(CLBR_ANY)
 	TRACE_IRQS_OFF
 	movl	%esp, %eax
@@ -372,7 +371,6 @@ syscall_call:
 syscall_after_call:
 	movl	%eax, PT_EAX(%esp)		# store the return value
 syscall_exit:
-	LOCKDEP_SYS_EXIT
 	jmp	syscall_exit_work
 
 restore_all:

arch/x86/entry/entry_64.S

@@ -557,7 +557,6 @@ ret_from_intr:
 	jz	retint_kernel
 
 	/* Interrupt came from user space */
-	LOCKDEP_SYS_EXIT_IRQ
 GLOBAL(retint_user)
 	mov	%rsp,%rdi
 	call	prepare_exit_to_usermode