schedule: ll: dynamically allocate the semaphore

[lyakh]

The LL scheduler semaphore is used by the userspace, so it has to be allocated dynamically. On the other hand dynamic object freeing from the userspace is unsupported by design. To securely free the semaphore object we add two syscalls that guarantee, that object freeing cannot be abused.

[Copilot]

Pull request overview

This PR updates the Zephyr LL scheduler task teardown path to use a dynamically allocated k_sem (needed for userspace access), and introduces new syscall entry points to allocate/free that semaphore in a controlled way.

Changes:

• Switch LL task private data from an embedded struct k_sem to a dynamically allocated struct k_sem *.
• Add semaphore alloc/free syscall implementations and wire them into task init/free.
• Register ll_schedule_domain.h for Zephyr syscall header generation.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
zephyr/CMakeLists.txt	Adds ll_schedule_domain.h to the set of headers used for syscall generation.
src/schedule/zephyr_ll.c	Implements dynamic semaphore lifecycle, adds alloc/free syscalls, updates task init/free and access grants.
src/include/sof/schedule/ll_schedule_domain.h	Exposes new syscall prototypes (or z_impl_ fallbacks) for LL task semaphore alloc/free.

Suppressed comments (3)

src/schedule/zephyr_ll.c:463

• z_impl_zephyr_ll_task_sem_alloc() doesn’t validate task->priv_data and doesn’t guard against re-allocation (which can leak semaphores / list nodes). It also appends to the global list without locking.

int z_impl_zephyr_ll_task_sem_alloc(struct task *task)
{
	struct zephyr_ll_pdata *pdata = task->priv_data;
	struct zephyr_ll_task_sem *ts = rmalloc(SOF_MEM_FLAG_COHERENT, sizeof(*ts));

src/schedule/zephyr_ll.c:488

• z_impl_zephyr_ll_task_sem_free() can be called from userspace at any time and currently frees the semaphore as long as it finds a matching entry. This can lead to use-after-free (e.g., zephyr_ll_task_free()/zephyr_ll_task_done() will later k_sem_take/give the freed semaphore). At minimum, gate freeing to the task-free path (e.g., require pdata->freeing) and serialize access to the global list.

	struct zephyr_ll_pdata *pdata = task->priv_data;
	struct list_item *list;
	struct zephyr_ll_task_sem *ts;
	bool found = false;

src/schedule/zephyr_ll.c:600

• The return value of zephyr_ll_task_sem_free(task) is ignored. If freeing fails (e.g., due to an unexpected state), the code continues and frees pdata, potentially leaking the semaphore object / list node or leaving a dangling pdata->sem behind.

	zephyr_ll_task_sem_free(task);

[kv2019i]

Tested this today on device with LL-usespace build and seems to work fine.

[jsarha]

LGTM

[lyakh]

dynamic objects aren't available without CONFIG_USERSPACE, so, had to update