Linus Torvalds 9ad8d22f2f vfs-6.13.rust.pid_namespace ... -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCZzcWKgAKCRCRxhvAZXjc osPAAP9bLzOPIF51IgP9mQTBlKKrpCWCMQVss5xRDseyNEfCEQD/fR9TSSnX9Suw iad9oBkxkzCjyxWIH46rvbdnc38lRwo= =aawA -----END PGP SIGNATURE----- Merge tag 'vfs-6.13.rust.pid_namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs Pull pid_namespace rust bindings from Christian Brauner: "This contains my Rust bindings for pid namespaces needed for various rust drivers. Here's a description of the basic C semantics and how they are mapped to Rust. The pid namespace of a task doesn't ever change once the task is alive. A unshare(CLONE_NEWPID) or setns(fd_pidns/pidfd, CLONE_NEWPID) will not have an effect on the calling task's pid namespace. It will only effect the pid namespace of children created by the calling task. This invariant guarantees that after having acquired a reference to a task's pid namespace it will remain unchanged. When a task has exited and been reaped release_task() will be called. This will set the pid namespace of the task to NULL. So retrieving the pid namespace of a task that is dead will return NULL. Note, that neither holding the RCU lock nor holding a reference count to the task will prevent release_task() from being called. In order to retrieve the pid namespace of a task the task_active_pid_ns() function can be used. There are two cases to consider: (1) retrieving the pid namespace of the current task (2) retrieving the pid namespace of a non-current task From system call context retrieving the pid namespace for case (1) is always safe and requires neither RCU locking nor a reference count to be held. Retrieving the pid namespace after release_task() for current will return NULL but no codepath like that is exposed to Rust. Retrieving the pid namespace from system call context for (2) requires RCU protection. Accessing a pid namespace outside of RCU protection requires a reference count that must've been acquired while holding the RCU lock. Note that accessing a non-current task means NULL can be returned as the non-current task could have already passed through release_task(). To retrieve (1) the current_pid_ns!() macro should be used. It ensures that the returned pid namespace cannot outlive the calling scope. The associated current_pid_ns() function should not be called directly as it could be abused to created an unbounded lifetime for the pid namespace. The current_pid_ns!() macro allows Rust to handle the common case of accessing current's pid namespace without RCU protection and without having to acquire a reference count. For (2) the task_get_pid_ns() method must be used. This will always acquire a reference on the pid namespace and will return an Option to force the caller to explicitly handle the case where pid namespace is None. Something that tends to be forgotten when doing the equivalent operation in C. Missing RCU primitives make it difficult to perform operations that are otherwise safe without holding a reference count as long as RCU protection is guaranteed. But it is not important currently. But we do want it in the future. Note that for (2) the required RCU protection around calling task_active_pid_ns() synchronizes against putting the last reference of the associated struct pid of task->thread_pid. The struct pid stored in that field is used to retrieve the pid namespace of the caller. When release_task() is called task->thread_pid will be NULLed and put_pid() on said struct pid will be delayed in free_pid() via call_rcu() allowing everyone with an RCU protected access to the struct pid acquired from task->thread_pid to finish" * tag 'vfs-6.13.rust.pid_namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: rust: add PidNamespace		2024-11-26 13:18:00 -08:00
..
bindings	Add Rust support for trace events:	2024-11-25 15:44:29 -08:00
helpers	vfs-6.13.rust.pid_namespace	2024-11-26 13:18:00 -08:00
kernel	vfs-6.13.rust.pid_namespace	2024-11-26 13:18:00 -08:00
macros	Rust changes for v6.12	2024-09-25 10:25:40 -07:00
uapi	rust: net::phy unified read/write API for C22 and C45 registers	2024-08-30 10:27:35 +01:00
.gitignore	rust: support running Rust documentation tests as KUnit ones	2023-07-19 09:32:53 -06:00
bindgen_parameters	rust: fix ARCH_SLAB_MINALIGN multiple definition error	2024-09-26 17:52:35 +02:00
build_error.rs	rust: add build_error crate	2022-12-04 01:59:16 +01:00
compiler_builtins.rs	rust: add intrinsics to fix -Os builds	2024-08-10 00:05:10 +02:00
exports.c	rust: kbuild: auto generate helper exports	2024-08-19 11:09:02 +02:00
Makefile	rust: jump_label: skip formatting generated file	2024-11-20 13:32:42 -05:00