Bug#851729: hurd: exe filename missing for some processes

[Guillem Jover <guillem@debian.org>]

Package: hurd
Version: 1:0.9.git20170117-1
Severity: normal

Hi!

I was improving the support to get the process executable in
start-stop-daemon to use the new libps proc_stat_set_flags PSTAT_EXE
attribute, instead of having to use argv[0], and while testing I
noticed that several processes return empty filenames, which makes
this unreliable to use. :/

This is visible from the libps API and from /proc:

  ,---
  for l in /proc/*/exe; do n=$(readlink $l); test -z "$n" || continue;\
    echo "$l -> '$n'"; grep Name: /proc/$(echo $l|cut -d/ -f3)/status;\
    done
  /proc/12/exe -> ''
  Name:   mach-defpager
  /proc/2/exe -> ''
  Name:   startup
  /proc/3/exe -> ''
  Name:   gnumach
  /proc/4/exe -> ''
  Name:   proc
  /proc/5/exe -> ''
  Name:   ext2fs
  /proc/575/exe -> ''
  Name:   sshd
  /proc/6/exe -> ''
  Name:   exec
  /proc/601/exe -> ''
  Name:   sshd
  /proc/7/exe -> ''
  Name:   auth
  `---

Thanks,
Guillem