[Bug 1993995] [NEW] new pidfd_open wrapper from glibc2.36 is undocumented in manpages-dev

[Daniel Tang]

Public bug reported:

glibc2.36 shipping with Ubuntu 22.10 has pidfd_open and other pidfd_*
support. manpages-dev still reports "Note: glibc provides no wrapper for
pidfd_open(), necessitating the use of syscall(2)" and recommends the
less ideal `int syscall(SYS_pidfd_open [...]`. This is false, outdated,
and misleading.

This is a new behaviour this August 2022 according to
https://lists.gnu.org/archive/html/info-gnu/2022-08/msg00000.html . This
bug also exists in the upstream code at
https://git.kernel.org/pub/scm/docs/man-pages/man-
pages.git/tree/man2/pidfd_open.2?h=man-pages-6.01#n20 .

$ lsb_release -rd
Description:    Ubuntu 22.10
Release:        22.10

$ apt-cache policy manpages-dev
manpages-dev:
  Installed: 5.13-1
  Candidate: 5.13-1
  Version table:
 *** 5.13-1 500
        500 https://gpl.savoirfairelinux.net/pub/mirrors/ubuntu kinetic/main amd64 Packages
        500 https://gpl.savoirfairelinux.net/pub/mirrors/ubuntu kinetic/main i386 Packages
        100 /var/lib/dpkg/status

$ apt-cache policy libc6
libc6:
  Installed: 2.36-0ubuntu4
  Candidate: 2.36-0ubuntu4
  Version table:
 *** 2.36-0ubuntu4 500
        500 https://gpl.savoirfairelinux.net/pub/mirrors/ubuntu kinetic/main amd64 Packages
        100 /var/lib/dpkg/status

# Expected behaviour

The function exists from `#include <sys/pidfd.h>`. It should recommend
something like the line there with ```extern int pidfd_open (__pid_t
__pid, unsigned int __flags) __THROW;```.

$ readelf -Ws /lib/x86_64-linux-gnu/libc.so.6 | grep pidfd_open
  1425: 000000000011fbe0    37 FUNC    GLOBAL DEFAULT   16 pidfd_open@@GLIBC_2.36

# Actual behaviour

$ zcat /usr/share/man/man2/pidfd_open.2.gz | grep glibc
glibc provides no wrapper for
--- 
ProblemType: Bug
ApportVersion: 2.23.1-0ubuntu3
Architecture: amd64
CasperMD5CheckResult: unknown
Dependencies:
 
DistroRelease: Ubuntu 22.10
Package: manpages 5.13-1
PackageArchitecture: all
ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
Tags:  kinetic
Uname: Linux 6.0.1-surface x86_64
UpgradeStatus: Upgraded to kinetic on 2022-09-29 (25 days ago)
UserGroups: dialout docker kvm lpadmin lxd plugdev sudo systemd-journal video wireshark
_MarkForUpload: True

** Affects: glibc (Ubuntu)
     Importance: Undecided
         Status: New

** Affects: manpages (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: apport-collected kinetic

** Also affects: glibc (Ubuntu)
   Importance: Undecided
       Status: New

** Tags added: apport-collected kinetic

** Description changed:

  glibc2.36 shipping with Ubuntu 22.10 has pidfd_open and other pidfd_*
  support. manpages-dev still reports "Note: glibc provides no wrapper for
  pidfd_open(), necessitating the use of syscall(2)" and recommends the
  less ideal `int syscall(SYS_pidfd_open [...]`. This is false, outdated,
  and misleading.
  
  This is a new behaviour this August 2022 according to
  https://lists.gnu.org/archive/html/info-gnu/2022-08/msg00000.html . This
  bug also exists in the upstream code at
  https://git.kernel.org/pub/scm/docs/man-pages/man-
  pages.git/tree/man2/pidfd_open.2?h=man-pages-6.01#n20 .
  
  $ lsb_release -rd
  Description:    Ubuntu 22.10
  Release:        22.10
  
  $ apt-cache policy manpages-dev
  manpages-dev:
    Installed: 5.13-1
    Candidate: 5.13-1
    Version table:
   *** 5.13-1 500
          500 https://gpl.savoirfairelinux.net/pub/mirrors/ubuntu kinetic/main amd64 Packages
          500 https://gpl.savoirfairelinux.net/pub/mirrors/ubuntu kinetic/main i386 Packages
          100 /var/lib/dpkg/status
  
  $ apt-cache policy libc6
  libc6:
    Installed: 2.36-0ubuntu4
    Candidate: 2.36-0ubuntu4
    Version table:
   *** 2.36-0ubuntu4 500
          500 https://gpl.savoirfairelinux.net/pub/mirrors/ubuntu kinetic/main amd64 Packages
          100 /var/lib/dpkg/status
  
  # Expected behaviour
  
  The function exists from `#include <sys/pidfd.h>`. It should recommend
  something like the line there with ```extern int pidfd_open (__pid_t
  __pid, unsigned int __flags) __THROW;```.
  
  $ readelf -Ws /lib/x86_64-linux-gnu/libc.so.6 | grep pidfd_open
    1425: 000000000011fbe0    37 FUNC    GLOBAL DEFAULT   16 pidfd_open@@GLIBC_2.36
  
  # Actual behaviour
  
  $ zcat /usr/share/man/man2/pidfd_open.2.gz | grep glibc
  glibc provides no wrapper for
+ --- 
+ ProblemType: Bug
+ ApportVersion: 2.23.1-0ubuntu3
+ Architecture: amd64
+ CasperMD5CheckResult: unknown
+ Dependencies:
+  
+ DistroRelease: Ubuntu 22.10
+ Package: manpages 5.13-1
+ PackageArchitecture: all
+ ProcEnviron:
+  TERM=linux
+  PATH=(custom, no user)
+  XDG_RUNTIME_DIR=<set>
+  LANG=en_US.UTF-8
+  SHELL=/bin/bash
+ Tags:  kinetic
+ Uname: Linux 6.0.1-surface x86_64
+ UpgradeStatus: Upgraded to kinetic on 2022-09-29 (25 days ago)
+ UserGroups: dialout docker kvm lpadmin lxd plugdev sudo systemd-journal video wireshark
+ _MarkForUpload: True

-- 
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https://bugs.launchpad.net/bugs/1993995

Title:
  new pidfd_open wrapper from glibc2.36 is undocumented in manpages-dev

Status in glibc package in Ubuntu:
  New
Status in manpages package in Ubuntu:
  New

Bug description:
  glibc2.36 shipping with Ubuntu 22.10 has pidfd_open and other pidfd_*
  support. manpages-dev still reports "Note: glibc provides no wrapper
  for pidfd_open(), necessitating the use of syscall(2)" and recommends
  the less ideal `int syscall(SYS_pidfd_open [...]`. This is false,
  outdated, and misleading.

  This is a new behaviour this August 2022 according to
  https://lists.gnu.org/archive/html/info-gnu/2022-08/msg00000.html .
  This bug also exists in the upstream code at
  https://git.kernel.org/pub/scm/docs/man-pages/man-
  pages.git/tree/man2/pidfd_open.2?h=man-pages-6.01#n20 .

  $ lsb_release -rd
  Description:    Ubuntu 22.10
  Release:        22.10

  $ apt-cache policy manpages-dev
  manpages-dev:
    Installed: 5.13-1
    Candidate: 5.13-1
    Version table:
   *** 5.13-1 500
          500 https://gpl.savoirfairelinux.net/pub/mirrors/ubuntu kinetic/main amd64 Packages
          500 https://gpl.savoirfairelinux.net/pub/mirrors/ubuntu kinetic/main i386 Packages
          100 /var/lib/dpkg/status

  $ apt-cache policy libc6
  libc6:
    Installed: 2.36-0ubuntu4
    Candidate: 2.36-0ubuntu4
    Version table:
   *** 2.36-0ubuntu4 500
          500 https://gpl.savoirfairelinux.net/pub/mirrors/ubuntu kinetic/main amd64 Packages
          100 /var/lib/dpkg/status

  # Expected behaviour

  The function exists from `#include <sys/pidfd.h>`. It should recommend
  something like the line there with ```extern int pidfd_open (__pid_t
  __pid, unsigned int __flags) __THROW;```.

  $ readelf -Ws /lib/x86_64-linux-gnu/libc.so.6 | grep pidfd_open
    1425: 000000000011fbe0    37 FUNC    GLOBAL DEFAULT   16 pidfd_open@@GLIBC_2.36

  # Actual behaviour

  $ zcat /usr/share/man/man2/pidfd_open.2.gz | grep glibc
  glibc provides no wrapper for
  --- 
  ProblemType: Bug
  ApportVersion: 2.23.1-0ubuntu3
  Architecture: amd64
  CasperMD5CheckResult: unknown
  Dependencies:
   
  DistroRelease: Ubuntu 22.10
  Package: manpages 5.13-1
  PackageArchitecture: all
  ProcEnviron:
   TERM=linux
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  Tags:  kinetic
  Uname: Linux 6.0.1-surface x86_64
  UpgradeStatus: Upgraded to kinetic on 2022-09-29 (25 days ago)
  UserGroups: dialout docker kvm lpadmin lxd plugdev sudo systemd-journal video wireshark
  _MarkForUpload: True

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