[PATCH v14 0/4] Checkpoint Support for Syscall User Dispatch

Gregory Price
2023-03-28T16:48:30Z

v14: implement task_access_ok variant for cross-task pointer checks
patch 2/4 changed from access_ok to task_access_ok

v13: sizeof consistency and cosmetic changes in patch 2

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

[truncating 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:
- Create new task_access_ok which leverages the provided task's
information when validating userland pointers. For ARM64 this means
MTE tags are accounted for. For all other architectures, this simply
reduces to access_ok (presently).

- 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 (4):
asm-generic,arm64: create task variant of access_ok
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 ++
arch/arm64/include/asm/uaccess.h | 13 +++-
include/asm-generic/access_ok.h | 10 +++
include/linux/syscall_user_dispatch.h | 18 +++++
include/uapi/linux/ptrace.h | 29 ++++++++
kernel/entry/syscall_user_dispatch.c | 67 ++++++++++++++---
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 +++++++++++++++++++
10 files changed, 213 insertions(+), 12 deletions(-)
create mode 100644 tools/testing/selftests/ptrace/get_set_sud.c

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2.39.1