diff options
Diffstat (limited to 'arch/x86/entry/entry_64.S')
| -rw-r--r-- | arch/x86/entry/entry_64.S | 37 |
1 files changed, 17 insertions, 20 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index c1af8acd366b..c0373d667674 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -407,37 +407,34 @@ END(__switch_to_asm) * A newly forked process directly context switches into this address. * * rax: prev task we switched from + * rbx: kernel thread func (NULL for user thread) + * r12: kernel thread arg */ ENTRY(ret_from_fork) movq %rax, %rdi call schedule_tail /* rdi: 'prev' task parameter */ - testb $3, CS(%rsp) /* from kernel_thread? */ - jnz 1f - - /* - * We came from kernel_thread. This code path is quite twisted, and - * someone should clean it up. - * - * copy_thread_tls stashes the function pointer in RBX and the - * parameter to be passed in RBP. The called function is permitted - * to call do_execve and thereby jump to user mode. - */ - movq RBP(%rsp), %rdi - call *RBX(%rsp) - movl $0, RAX(%rsp) - - /* - * Fall through as though we're exiting a syscall. This makes a - * twisted sort of sense if we just called do_execve. - */ + testq %rbx, %rbx /* from kernel_thread? */ + jnz 1f /* kernel threads are uncommon */ -1: +2: movq %rsp, %rdi call syscall_return_slowpath /* returns with IRQs disabled */ TRACE_IRQS_ON /* user mode is traced as IRQS on */ SWAPGS jmp restore_regs_and_iret + +1: + /* kernel thread */ + movq %r12, %rdi + call *%rbx + /* + * A kernel thread is allowed to return here after successfully + * calling do_execve(). Exit to userspace to complete the execve() + * syscall. + */ + movq $0, RAX(%rsp) + jmp 2b END(ret_from_fork) /* |
