From 616d24835eeafa8ef3466479db028abfdfc77531 Mon Sep 17 00:00:00 2001 From: Brian Gerst Date: Sat, 13 Aug 2016 12:38:20 -0400 Subject: sched/x86: Pass kernel thread parameters in 'struct fork_frame' 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 Reviewed-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1471106302-10159-6-git-send-email-brgerst@gmail.com Signed-off-by: Ingo Molnar --- arch/x86/entry/entry_32.S | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-) (limited to 'arch/x86/entry/entry_32.S') diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index bf8f221f9c94..b75a8bcd2d23 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -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, -- cgit v1.2.3