On Sun, Jun 19, 2016 at 5:28 PM, Andy Lutomirski <l...@amacapital.net> wrote: > On Sat, Jun 18, 2016 at 1:56 PM, Brian Gerst <brge...@gmail.com> wrote: >> 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. > > This seems generally okay. > >> >> Signed-off-by: Brian Gerst <brge...@gmail.com> > >> @@ -146,19 +147,12 @@ int copy_thread_tls(unsigned long clone_flags, >> unsigned long sp, > > >> if (unlikely(p->flags & PF_KTHREAD)) { >> /* kernel thread */ >> memset(childregs, 0, sizeof(struct pt_regs)); >> - frame->ret_addr = (unsigned long) ret_from_kernel_thread; >> - task_user_gs(p) = __KERNEL_STACK_CANARY; >> - childregs->ds = __USER_DS; >> - childregs->es = __USER_DS; >> - childregs->fs = __KERNEL_PERCPU; > > Is the idea that do_execve promises to initialize all these fields to > something sensible if the kernel thread in question tries to return to > user mode? > > --Andy
Yes, do_execve() should be setting the full pt_regs. -- Brian Gerst