Messages in this thread | | | Date | Wed, 28 Sep 2011 17:55:39 +0200 | From | Oleg Nesterov <> | Subject | Re: Q: x86: add context tag to mark mm when running a task in 32-bit compatibility mode |
| |
On 09/27, Al Viro wrote: > > On Tue, Sep 27, 2011 at 07:04:48PM +0200, Oleg Nesterov wrote: > > --- x/arch/x86/kernel/process_64.c > > +++ x/arch/x86/kernel/process_64.c > > @@ -502,10 +502,6 @@ void set_personality_64bit(void) > > /* Make sure to be in 64bit mode */ > > clear_thread_flag(TIF_IA32); > > > > - /* Ensure the corresponding mm is not marked. */ > > - if (current->mm) > > - current->mm->context.ia32_compat = 0; > > What happens when 32bit task does exec on 64bit binary?
Nothing. This bit is always zero after init_mm(), it can't copy MMF_COMPAT.
But. This is wrong anyway. I forgot about fork(). We do not want to uglify copy_mm(), MMF_INIT_MASK should include MMF_COMPAT and then set_personality_64bit() needs to clear this bit.
Thanks!
> > - if (current->mm) > > - current->mm->context.ia32_compat = 1; > > + set_bit(MMF_COMPAT, ¤t->mm->flags); > > ... assuming current->mm is never NULL here.
Yes, but it can't be NULL?
SET_PERSONALITY() can only be called during exec, and it must be called after exec_mmap() has already installed the new mm != NULL, otherwise the current code is buggy anyway.
Oleg.
| |