Re: [PATCH v2 3/3] linux: Add pidfd_getpid

[Luca Boccassi <luca.boccassi@gmail.com>]

On Tue, 2 May 2023 at 17:07, Florian Weimer <fweimer@redhat.com> wrote:
>
> * Adhemerval Zanella via Libc-alpha:
> > diff --git a/sysdeps/unix/sysv/linux/pidfd_getpid.c b/sysdeps/unix/sysv/linux/pidfd_getpid.c
> > new file mode 100644
> > index 0000000000..d0c7987791
> > --- /dev/null
> > +++ b/sysdeps/unix/sysv/linux/pidfd_getpid.c
> > @@ -0,0 +1,94 @@
>
> > +static bool
> > +parse_fdinfo (const char *l, void *arg)
> > +{
> > +  enum { fieldlen = sizeof ("Pid:") - 1 };
> > +  if (strncmp (l, "Pid:", fieldlen) != 0)
> > +    return true;
> > +
> > +  l += fieldlen;
> > +
> > +  char *endp;
> > +  long int n = strtol (l, &endp, 10);
> > +  if (l == endp || n > INT_MAX)
> > +    return true;
>
> Should this use strtoul?  Otherwise I'm not sure the overflow check will
> work on 32-bit.
>
> Rest of the implementation looks okay, but the kernel should really
> provide an ioctl or similar for this.

This can be -1 when the process is gone, and it is important to get
that distinction (with certainty) to tell the caller ESRCH. We need
this distinction in callers.

Kind regards,
Luca Boccassi