Disclaimer: I'm looking at this patch because Christian requested it.
I'm not a kernel developer.
* Christian Brauner:
> diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
> index 3cf7b533b3d1..3f27ffd8ae87 100644
> --- a/arch/x86/entry/syscalls/syscall_32.tbl
> +++ b/arch/x86/entry/syscalls/syscall_32.tbl
> @@ -398,3 +398,4 @@
> 384 i386 arch_prctl sys_arch_prctl __ia32_compat_sys_arch_prctl
> 385 i386 io_pgetevents sys_io_pgetevents __ia32_compat_sys_io_pgetevents
> 386 i386 rseq sys_rseq __ia32_sys_rseq
> +387 i386 procfd_signal sys_procfd_signal __ia32_compat_sys_procfd_signal
> diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
> index f0b1709a5ffb..8a30cde82450 100644
> --- a/arch/x86/entry/syscalls/syscall_64.tbl
> +++ b/arch/x86/entry/syscalls/syscall_64.tbl
> @@ -343,6 +343,7 @@
> 332 common statx __x64_sys_statx
> 333 common io_pgetevents __x64_sys_io_pgetevents
> 334 common rseq __x64_sys_rseq
> +335 64 procfd_signal __x64_sys_procfd_signal
>
> #
> # x32-specific system call numbers start at 512 to avoid cache impact
> @@ -386,3 +387,4 @@
> 545 x32 execveat __x32_compat_sys_execveat/ptregs
> 546 x32 preadv2 __x32_compat_sys_preadv64v2
> 547 x32 pwritev2 __x32_compat_sys_pwritev64v2
> +548 x32 procfd_signal __x32_compat_sys_procfd_signal
Is there a reason why these numbers have to be different?
(See the recent discussion with Andy Lutomirski.)
> +static int do_procfd_signal(int fd, int sig, kernel_siginfo_t *kinfo, int flags,
> + bool had_siginfo)
> +{
> + int ret;
> + struct fd f;
> + struct pid *pid;
> +
> + /* Enforce flags be set to 0 until we add an extension. */
> + if (flags)
> + return -EINVAL;
> +
> + f = fdget_raw(fd);
> + if (!f.file)
> + return -EBADF;
> +
> + /* Is this a process file descriptor? */
> + ret = -EINVAL;
> + if (!proc_is_tgid_procfd(f.file))
> + goto err;
[…]
> + ret = kill_pid_info(sig, kinfo, pid);
I would like to see some comment here what happens to zombie processes.
> +/**
> + * sys_procfd_signal - send a signal to a process through a process file
> + * descriptor
> + * @fd: the file descriptor of the process
> + * @sig: signal to be sent
> + * @info: the signal info
> + * @flags: future flags to be passed
> + */
> +SYSCALL_DEFINE4(procfd_signal, int, fd, int, sig, siginfo_t __user *, info,
> + int, flags)
Sorry, I'm quite unhappy with the name. “signal” is for signal handler
management. procfd_sendsignal, procfd_sigqueueinfo or something like
that would be fine. Even procfd_kill would be better IMHO.
Looking at the rt_tgsigqueueinfo interface, is there a way to implement
the “tg” part with the current procfd_signal interface? Would you use
openat to retrieve the Tgid: line from "status"?
Thanks,
Florian
