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sched/x86: Pass kernel thread parameters in 'struct fork_frame'

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Instead of setting up a fake pt_regs context, put the kernel thread
function pointer and arg into the unused callee-restored registers
of 'struct fork_frame'.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
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>
Link: http://lkml.kernel.org/r/1471106302-10159-6-git-send-email-brgerst@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Brian Gerst
2016-08-13 12:38:20 -04:00
committed by Ingo Molnar
parent 0100301bfd
commit 616d24835e
5 changed files with 41 additions and 59 deletions
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31
arch/x86/entry/entry_32.S
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@@ -240,35 +240,34 @@ END(__switch_to_asm)
* A newly forked process directly context switches into this address.
*
* eax: prev task we switched from
* ebx: kernel thread func (NULL for user thread)
* edi: kernel thread arg
*/
ENTRY(ret_from_fork)
pushl %eax
call schedule_tail
popl %eax
testl %ebx, %ebx
jnz 1f /* kernel threads are uncommon */
2:
/* 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)
pushl %eax
call schedule_tail
popl %eax
movl PT_EBP(%esp), %eax
call *PT_EBX(%esp)
movl $0, PT_EAX(%esp)
/* kernel thread */
1: movl %edi, %eax
call *%ebx
/*
* 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.
* A kernel thread is allowed to return here after successfully
* calling do_execve(). Exit to userspace to complete the execve()
* syscall.
*/
movl %esp, %eax
call syscall_return_slowpath
jmp restore_all
ENDPROC(ret_from_kernel_thread)
movl $0, PT_EAX(%esp)
jmp 2b
END(ret_from_fork)
/*
* Return to user mode is not as complex as all this looks,