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Commit 39e8701f authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/entry/32: Open-code return tracking from fork and kthreads 



syscall_exit is going away, and return tracing is just a
function call now, so open-code the two non-syscall 32-bit
users.

While we're at it, update the big register layout comment.

Signed-off-by: default avatarAndy 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/a6b3c472fda7cda0e368c3ccd553dea7447dfdd2.1444091585.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 7841b408

arch/x86/entry/entry_32.S

+15 −3
Original line number Diff line number Diff line
@@ -3,7 +3,7 @@ 
 *

 * entry_32.S contains the system-call and low-level fault and trap handling routines.

 *

 * Stack layout in 'syscall_exit':

 * Stack layout while running C code:

 *	ptrace needs to have all registers on the stack.

 *	If the order here is changed, it needs to be

 *	updated in fork.c:copy_process(), signal.c:do_signal(),
@@ -211,7 +211,11 @@ ENTRY(ret_from_fork) 
	popl	%eax

	pushl	$0x0202				# Reset kernel eflags

	popfl

	jmp	syscall_exit



	/* When we fork, we trace the syscall return in the child, too. */

	movl    %esp, %eax

	call    syscall_return_slowpath

	jmp     restore_all

END(ret_from_fork)



ENTRY(ret_from_kernel_thread)
@@ -224,7 +228,15 @@ ENTRY(ret_from_kernel_thread) 
	movl	PT_EBP(%esp), %eax

	call	*PT_EBX(%esp)

	movl	$0, PT_EAX(%esp)

	jmp	syscall_exit



	/*

	 * Kernel threads return to userspace as if returning from a syscall.

	 * We should check whether anything actually uses this path and, if so,

	 * consider switching it over to ret_from_fork.

	 */

	movl    %esp, %eax

	call    syscall_return_slowpath

	jmp     restore_all

ENDPROC(ret_from_kernel_thread)



/*