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SubjectRe: [PATCH v2] signal: add procfd_signal() syscall
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> On Dec 1, 2018, at 7:28 AM, Eric W. Biederman <ebiederm@xmission.com> wrote:
>
>
> It just occurs to me that the simple way to implement
> procfd_sigqueueinfo info is like:
>
> int copy_siginfo_from_user_any(kernel_siginfo_t *info, siginfo_t *uinfo)
> {
> #ifdef CONFIG_COMPAT
> if (in_compat_syscall)
> return copy_siginfo_from_user32(info, uinfo);
> #endif
> return copy_siginfo_from_user(info, uinfo);
> }
>
> long procfd_sigqueueinfo(int fd, siginfo_t *uinfo)
> {
> kernel_siginfo info;
>
> if (copy_siginfo_from_user_any(&info, uinfo))
> return -EFAULT;
> ...;
> }
>
> It looks like there is already a place in ptrace.c that already
> hand rolls copy_siginfo_from_user_any.
>
> So while I would love to figure out the subset of siginfo_t tha we can
> just pass through, as I think that would make a better more forward
> compatible copy_siginfo_from_user32.

Seems reasonable to me. It’s less code overall than any other suggestion, too.

> I think for this use case we just
> add the in_compat_syscall test and then we just need to ensure this new
> system call is placed in the proper places in the syscall table.
>
> Because we will need 3 call sights: x86_64, x32 and ia32. As the layout
> changes between those three subarchitecuters.
>
>

If it’s done this way, it can just be “common” in the 64-bit table. And we kick the can a bit farther down the road :)

I’m working on patches to clean up x86’s syscall mess. It’s slow because I keep finding new messes. So far I have rt_sigreturn working like every other syscall — whee.

Also, Eric, for your edification, I have a draft patch set to radically simplify x86’s signal delivery and return. Once that’s done, I can trivially speed up delivery by a ton by using sysret.


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