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x86/entry/32: Open-code return tracking from fork and kthreads

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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: 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/a6b3c472fda7cda0e368c3ccd553dea7447dfdd2.1444091585.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-10-05 17:48:13 -07:00 • committed by Ingo Molnar
parent 7841b40871
commit 39e8701f33
1 changed files with 15 additions and 3 deletions
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18
arch/x86/entry/entry_32.S
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@ -3,7 +3,7 @@
* *
* entry_32.S contains the system-call and low-level fault and trap handling routines. * 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. * ptrace needs to have all registers on the stack.
* If the order here is changed, it needs to be * If the order here is changed, it needs to be
* updated in fork.c:copy_process(), signal.c:do_signal(), * updated in fork.c:copy_process(), signal.c:do_signal(),
@ -211,7 +211,11 @@ ENTRY(ret_from_fork)
popl %eax popl %eax
pushl $0x0202 # Reset kernel eflags pushl $0x0202 # Reset kernel eflags
popfl 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) END(ret_from_fork)
ENTRY(ret_from_kernel_thread) ENTRY(ret_from_kernel_thread)
@ -224,7 +228,15 @@ ENTRY(ret_from_kernel_thread)
movl PT_EBP(%esp), %eax movl PT_EBP(%esp), %eax
call *PT_EBX(%esp) call *PT_EBX(%esp)
movl $0, PT_EAX(%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) ENDPROC(ret_from_kernel_thread)
/* /*