v5: automated test for !defined(GENERIC_ENTRY) failed, fix fs/proc use ifdef for GENERIC_ENTRY || TIF_SYSCALL_USER_DISPATCH note: syscall user dispatch is not presently supported for non-generic entry, but could be implemented. question is whether the TIF_ define should be carved out now or then
v4: Whitespace s/CHECKPOINT_RESTART/CHECKPOINT_RESUME check test_syscall_work(SYSCALL_USER_DISPATCH) to determine if it's turned on or not in fs/proc/array and getter interface
v3: Kernel test robot static function fix Whitespace nitpicks
v2: Implements the getter/setter interface in ptrace rather than prctl
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.
This patch set implements 3 features to enable software such as CRIU to cleanly interpose upon software leveraging syscall user dispatch.
- Implement PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH, akin to a similar feature for SECCOMP. This allows a ptracer to temporarily disable syscall user dispatch, making syscall injection possible.
- Implement an fs/proc extension that reports whether Syscall User Dispatch is being used in proc/status. A similar value is present for SECCOMP, and is used to determine whether special logic is needed during checkpoint/resume.
- 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.
Gregory Price (3): ptrace,syscall_user_dispatch: Implement Syscall User Dispatch Suspension fs/proc/array: Add Syscall User Dispatch to proc status ptrace,syscall_user_dispatch: add a getter/setter for sud configuration
.../admin-guide/syscall-user-dispatch.rst | 5 +- fs/proc/array.c | 10 ++++ include/linux/ptrace.h | 2 + include/linux/syscall_user_dispatch.h | 19 +++++++ include/uapi/linux/ptrace.h | 16 +++++- kernel/entry/syscall_user_dispatch.c | 51 +++++++++++++++++++ kernel/ptrace.c | 13 +++++ 7 files changed, 114 insertions(+), 2 deletions(-)