Messages in this thread | | | Date | Thu, 30 Mar 2017 17:28:48 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/1] get_nr_restart_syscall() should return __NR_ia32_restart_syscall if __USER32_CS |
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On 03/29, Andy Lutomirski wrote: > > On Wed, Mar 29, 2017 at 8:05 AM, Oleg Nesterov <oleg@redhat.com> wrote: > > On 03/28, Oleg Nesterov wrote: > >> > >> On 03/28, Andy Lutomirski wrote: > >> > > >> > How about we store the syscall arch to be restored in task_struct > >> > along with restart_block? > >> > >> Yes, perhaps we will have to finally do this. Not really nice too. > > > > OK, how about the hack below? > > > > I do not want to a new member into task_struct/restart_block, so the > > patch below adds a sticky TS_COMPAT bit which logically is a member > > of "struct restart_block". > > Okay, but I'd much rather we just added a helper that's called in the > few places that actually write to restart_block.
Oh, yes, I thought about this too. This obviously needs more changes, and every arch needs a dummy definition... I was thinking about
static inline long setup_restart_block(void) { if (TS_COMPAT) set TS_COMPAT_XXX; else clear TS_COMPAT_XXX;
return -ERESTART_RESTARTBLOCK; }
so that we can do
- ret = -ERESTART_RESTARTBLOCK; + ret = setup_restart_block();
but I don't really like this... Do you strongly prefer it over the -ERESTART_RESTARTBLOCK check in syscall_return_slowpath? I agree it doesn't look nice too but it connects to other TS_ magic we do in arch/x86/entry/, perhaps it is not that bad...
> Or we just add the new syscall nr and see what breaks. The answer > could well be nothing at all.
Well, strace knows about __NR_restart_syscall. It won't be really broken, but I guess it will report something like "unknown syscall" rather than restart_syscall(...).
However, this still looks like a best solution to me, just I have no idea how much we can confuse user-space.
Oleg.
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