Messages in this thread | | | From | Andy Lutomirski <> | Date | Tue, 20 Sep 2016 23:39:35 -0700 | Subject | Re: [PATCH 3/9] x86/entry/32: fix the end of the stack for newly forked tasks |
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On Sep 20, 2016 5:25 PM, "Josh Poimboeuf" <jpoimboe@redhat.com> wrote: > > On Tue, Sep 20, 2016 at 09:10:55PM -0400, Brian Gerst wrote: > > Dropping asmlinkage from schedule_tail() would be a better option if possible. > > My understanding is that it's still needed for ia64. AFAICT, ia64 > relies on schedule_tail() having the syscall_linkage function attribute. > From the gcc manual: > > This attribute is used to modify the IA64 calling convention by > marking all input registers as live at all function exits. This makes > it possible to restart a system call after an interrupt without having > to save/restore the input registers. This also prevents kernel data > from leaking into application code.
/me needs to excise this from i386. The amount of BS code involved to avoid a whopping *six* register saves per syscall was absurd.
> > And the ia64 entry code has some similar language: > > /* > * Invoke schedule_tail(task) while preserving in0-in7, which may be needed > * in case a system call gets restarted. > */ > GLOBAL_ENTRY(ia64_invoke_schedule_tail) > ...
That comment has to be wrong. What syscall could possibly be restarted across schedule_tail()? It's a brand new thread and has literally never done a syscall.
There may be another reason that the registers are live there, but I generally do my best to never look at ia64 asm code.
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