linux-kernel - [PATCH v12 0/3] Checkpoint Support for Syscall User Dispatch

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Message-Id: <20230224233126.1936-1-gregory.price@memverge.com>
Date:   Fri, 24 Feb 2023 18:31:23 -0500
From:   Gregory Price <gourry.memverge@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-doc@...r.kernel.org, oleg@...hat.com, avagin@...il.com,
        peterz@...radead.org, luto@...nel.org, krisman@...labora.com,
        tglx@...utronix.de, corbet@....net, shuah@...nel.org,
        Gregory Price <gregory.price@...verge.com>
Subject: [PATCH v12 0/3] Checkpoint Support for Syscall User Dispatch

v12: split test into its own patch
     change from padding a u8 to using a u64
     casting issues
     checkpatch.pl

v11: backout complex compat code, change struct to more generic typing
     (padding to ensure struct size is the same in 32 compat)
     update selftest
     tested selftest on 64 machine and in 32-bit compat mode

v10: move refactor code into patch ahead of change
     add compat support
     documentation change

v9: tglx feedback
    whitespace
    documentation of ptrace struct
    shorten struct name
    helper function for set_syscall_user_dispatch
    use task variant of set/clear_syscall_work
    use task variant of test_syscall_work in getter
    selftest

[truncated version history]

Syscall user dispatch makes it possible to cleanly intercept system
calls from user-land.  However, most transparent checkpoint software
presently leverages some combination of ptrace and system call
injection to place software in a ready-to-checkpoint state.

If Syscall User Dispatch is enabled at the time of being quiesced,
injected system calls will subsequently be interposed upon and
dispatched to the task's signal handler.

Patch summary:
- Refactor configuration setting interface to operate on a task
  rather than current, so the set and error paths can be consolidated

- Implement a getter interface for Syscall User Dispatch config info.
  To resume successfully, the checkpoint/resume software has to
  save and restore this information.  Presently this configuration
  is write-only, with no way for C/R software to save it.

  This was done in ptrace because syscall user dispatch is not part of
  uapi. The syscall_user_dispatch_config structure was added to the
  ptrace exports.

- Selftest for the new feature

Gregory Price (3):
  syscall_user_dispatch: helper function to operate on given task
  ptrace,syscall_user_dispatch: checkpoint/restore support for SUD
  selftest,ptrace: Add selftest for syscall user dispatch config api

 .../admin-guide/syscall-user-dispatch.rst     |  4 ++
 include/linux/syscall_user_dispatch.h         | 18 +++++
 include/uapi/linux/ptrace.h                   | 29 ++++++++
 kernel/entry/syscall_user_dispatch.c          | 65 ++++++++++++++---
 kernel/ptrace.c                               |  9 +++
 tools/testing/selftests/ptrace/.gitignore     |  1 +
 tools/testing/selftests/ptrace/Makefile       |  2 +-
 tools/testing/selftests/ptrace/get_set_sud.c  | 72 +++++++++++++++++++
 8 files changed, 191 insertions(+), 9 deletions(-)
 create mode 100644 tools/testing/selftests/ptrace/get_set_sud.c

-- 
2.39.1