[PATCH v2 00/16] fchroot: add fchroot() testing suite

fchroot() is a new syscall introduced in the Linux v7.3 development
cycle together with failfs, a kernel internal filesystem where every
operation fails with EOPNOTSUPP. The syscall is the fd-based
counterpart of chroot(2): it moves the process root to the directory
referenced by a file descriptor, or to the failfs root via the
FD_FAILFS_ROOT sentinel.

The series first updates the architecture syscall number tables and
adds lapi fallback definitions for the new fd sentinels, then adds 13
tests covering:

- the basic directory fd use case and the argument error paths
  (EINVAL, EBADF, ENOTDIR)
- the permission checks, both execute permission and CAP_SYS_CHROOT
- entering failfs as root: EOPNOTSUPP on every absolute lookup,
  unreachable working directory, root that can not be referenced or
  pinned, path walks anchored at file descriptors, execve blocked,
  fork inheritance and the setns() escape
- the unprivileged entry rules: no_new_privs, shared fs_struct and
  the already chrooted case

fchroot() is not part of any released kernel yet, so the tests are
added to runtest/staging and each patch carries the [STAGING] prefix
as required by the LTP ground rules.

The testing suite creation has been assisted by GLM 5.3.

Signed-off-by: Andrea Cervesato <andrea.cervesato-IBi9RG/[email protected]>
---
Changes in v2:
- make description more readable
- invert fork() logic for the main test process
- fix the issues found by the agent
- Link to v1: https://lore.kernel.org/20260819-fchroot-v1-0-2dc2c3c3cf29-IBi9RG/[email protected]

To: Linux Test Project <[email protected]>

---
Andrea Cervesato (16):
      syscalls: add v7.3 syscall numbers
      syscalls: update outdated syscall entries
      [STAGING] lapi: fallback fchroot() parameters
      [STAGING] fchroot01: test fchroot() with a directory fd
      [STAGING] fchroot02: test fchroot() invalid arguments
      [STAGING] fchroot03: test fchroot() permission checks
      [STAGING] fchroot04: test fchroot() into failfs as root
      [STAGING] fchroot05: test failfs root can not be referenced
      [STAGING] fchroot06: test path walks under failfs root
      [STAGING] fchroot07: test execve blocked by failfs root
      [STAGING] fchroot08: test failfs root fork inheritance
      [STAGING] fchroot09: test setns escape from failfs root
      [STAGING] fchroot10: test failfs entry without no_new_privs
      [STAGING] fchroot11: test failfs entry with no_new_privs
      [STAGING] fchroot12: test failfs entry with shared fs_struct
      [STAGING] fchroot13: test failfs entry when chrooted

 include/lapi/fcntl.h                          |  13 +++
 include/lapi/syscalls/arc.in                  |   3 +
 include/lapi/syscalls/arm.in                  |   4 +-
 include/lapi/syscalls/arm64.in                |   3 +
 include/lapi/syscalls/i386.in                 |   4 +-
 include/lapi/syscalls/loongarch64.in          |   3 +
 include/lapi/syscalls/mips64.in               |   5 +-
 include/lapi/syscalls/mips64n32.in            |   5 +-
 include/lapi/syscalls/mipso32.in              |   5 +-
 include/lapi/syscalls/parisc.in               |   4 +-
 include/lapi/syscalls/powerpc.in              |   4 +-
 include/lapi/syscalls/powerpc64.in            |   4 +-
 include/lapi/syscalls/s390.in                 |   5 +-
 include/lapi/syscalls/s390x.in                |   5 +-
 include/lapi/syscalls/sh.in                   |   4 +-
 include/lapi/syscalls/sparc.in                |   5 +-
 include/lapi/syscalls/sparc64.in              |   5 +-
 include/lapi/syscalls/x86_64.in               |   5 +-
 runtest/staging                               |  14 +++
 testcases/kernel/syscalls/fchroot/.gitignore  |  13 +++
 testcases/kernel/syscalls/fchroot/Makefile    |   7 ++
 testcases/kernel/syscalls/fchroot/fchroot01.c |  59 +++++++++++++
 testcases/kernel/syscalls/fchroot/fchroot02.c |  80 ++++++++++++++++++
 testcases/kernel/syscalls/fchroot/fchroot03.c |  78 +++++++++++++++++
 testcases/kernel/syscalls/fchroot/fchroot04.c |  70 +++++++++++++++
 testcases/kernel/syscalls/fchroot/fchroot05.c |  75 +++++++++++++++++
 testcases/kernel/syscalls/fchroot/fchroot06.c | 117 ++++++++++++++++++++++++++
 testcases/kernel/syscalls/fchroot/fchroot07.c |  72 ++++++++++++++++
 testcases/kernel/syscalls/fchroot/fchroot08.c |  69 +++++++++++++++
 testcases/kernel/syscalls/fchroot/fchroot09.c |  87 +++++++++++++++++++
 testcases/kernel/syscalls/fchroot/fchroot10.c |  50 +++++++++++
 testcases/kernel/syscalls/fchroot/fchroot11.c |  70 +++++++++++++++
 testcases/kernel/syscalls/fchroot/fchroot12.c |  85 +++++++++++++++++++
 testcases/kernel/syscalls/fchroot/fchroot13.c |  63 ++++++++++++++
 34 files changed, 1076 insertions(+), 19 deletions(-)
---
base-commit: 567528e2f809c1309802433703c083bd15ab81a8
change-id: 20260819-fchroot-66115fd0d497

Best regards,
--  
Andrea Cervesato <andrea.cervesato-IBi9RG/[email protected]>


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