Messages in this thread | | | From | Linus Torvalds <> | Date | Wed, 29 Mar 2017 09:45:12 -0700 | Subject | Re: syscall_get_error() && TS_ checks |
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On Wed, Mar 29, 2017 at 9:33 AM, Oleg Nesterov <oleg@redhat.com> wrote: > > Firstly, why do we need the IS_ERR_VALUE() check? This is only used by > do_signal/handle_signal, we do not care if it returns non-zero as long > as the value can't be confused with -ERESTART.* codes.
There are system calls that can return "negative" values that aren't errors.
Notably mmap() can return a valid pointer with the high bit set.
So syscall_get_error() should return 0 for not just positive return values, but for those kinds of negative non-error values.
> And why do we need the TS_ checks?
Those may be bogus.
> So why we can't simply change putreg32() to always sign-extend regs->ax > regs->orig_ax and just do > > static inline long syscall_get_error(struct task_struct *task, > struct pt_regs *regs) > { > return regs-ax; > }
That would be *complete* garbage. Lots of system calls return positive values that sure as hell aren't errors.
Linus
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