Re: [PATCH v2] signal: add procfd_signal() syscall

On December 2, 2018 4:52:37 AM GMT+13:00, Andy Lutomirski [off-list ref] wrote:

quoted

On Dec 1, 2018, at 7:28 AM, Eric W. Biederman [off-list ref]

wrote:

quoted

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)

quoted

{
#ifdef CONFIG_COMPAT
   if (in_compat_syscall)
       return copy_siginfo_from_user32(info, uinfo);
#endif
   return copy_siginfo_from_user(info, uinfo);                       

quoted

}

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

quoted

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.

Thanks everyone, that was super helpful!
All things equal I'm going to send out an
updated version of the patch latest next week!

quoted

 I think for this use case we just
add the in_compat_syscall test and then we just need to ensure this

new

quoted

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

quoted

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.