Sasha Levin <sashal@xxxxxxxxxx> writes: > So I have a proof of concept which during the build process creates > .apispec.h which are generated from kerneldoc and contain macros > identical to the ones in my RFC. > > Here's an example of sys_mlock() spec: So I'm getting ahead of the game, but I have to ask some questions... > /** > * sys_mlock - Lock pages in memory > * @start: Starting address of memory range to lock > * @len: Length of memory range to lock in bytes > * > * Locks pages in the specified address range into RAM, preventing them from > * being paged to swap. Requires CAP_IPC_LOCK capability or RLIMIT_MEMLOCK > * resource limit. > * > * long-desc: Locks pages in the specified address range into RAM, preventing > * them from being paged to swap. Requires CAP_IPC_LOCK capability > * or RLIMIT_MEMLOCK resource limit. Why duplicate the long description? > * context-flags: KAPI_CTX_PROCESS | KAPI_CTX_SLEEPABLE > * param-type: start, KAPI_TYPE_UINT This is something I wondered before; rather than a bunch of lengthy KAPI_* symbols, why not just say __u64 (or some other familiar type) here? > * param-flags: start, KAPI_PARAM_IN > * param-constraint-type: start, KAPI_CONSTRAINT_NONE > * param-constraint: start, Rounded down to page boundary > * param-type: len, KAPI_TYPE_UINT > * param-flags: len, KAPI_PARAM_IN > * param-constraint-type: len, KAPI_CONSTRAINT_RANGE > * param-range: len, 0, LONG_MAX > * param-constraint: len, Rounded up to page boundary > * return-type: KAPI_TYPE_INT > * return-check-type: KAPI_RETURN_ERROR_CHECK > * return-success: 0 > * error-code: -ENOMEM, ENOMEM, Address range issue, > * Some of the specified range is not mapped, has unmapped gaps, > * or the lock would cause the number of mapped regions to exceed the limit. > * error-code: -EPERM, EPERM, Insufficient privileges, > * The caller is not privileged (no CAP_IPC_LOCK) and RLIMIT_MEMLOCK is 0. > * error-code: -EINVAL, EINVAL, Address overflow, > * The result of the addition start+len was less than start (arithmetic overflow). > * error-code: -EAGAIN, EAGAIN, Some or all memory could not be locked, > * Some or all of the specified address range could not be locked. > * error-code: -EINTR, EINTR, Interrupted by signal, > * The operation was interrupted by a fatal signal before completion. > * error-code: -EFAULT, EFAULT, Bad address, > * The specified address range contains invalid addresses that cannot be accessed. > * since-version: 2.0 > * lock: mmap_lock, KAPI_LOCK_RWLOCK > * lock-acquired: true > * lock-released: true > * lock-desc: Process memory map write lock > * signal: FATAL > * signal-direction: KAPI_SIGNAL_RECEIVE > * signal-action: KAPI_SIGNAL_ACTION_RETURN > * signal-condition: Fatal signal pending > * signal-desc: Fatal signals (SIGKILL) can interrupt the operation at two points: > * when acquiring mmap_write_lock_killable() and during page population > * in __mm_populate(). Returns -EINTR. Non-fatal signals do NOT interrupt > * mlock - the operation continues even if SIGINT/SIGTERM are received. > * signal-error: -EINTR > * signal-timing: KAPI_SIGNAL_TIME_DURING > * signal-priority: 0 > * signal-interruptible: yes > * signal-state-req: KAPI_SIGNAL_STATE_RUNNING > * examples: mlock(addr, 4096); // Lock one page > * mlock(addr, len); // Lock range of pages > * notes: Memory locks do not stack - multiple calls on the same range can be > * undone by a single munlock. Locks are not inherited by child processes. > * Pages are locked on whole page boundaries. Commonly used by real-time > * applications to prevent page faults during time-critical operations. > * Also used for security to prevent sensitive data (e.g., cryptographic keys) > * from being written to swap. Note: locked pages may still be saved to > * swap during system suspend/hibernate. > * > * Tagged addresses are automatically handled via untagged_addr(). The operation > * occurs in two phases: first VMAs are marked with VM_LOCKED, then pages are > * populated into memory. When checking RLIMIT_MEMLOCK, the kernel optimizes > * by recounting locked memory to avoid double-counting overlapping regions. > * side-effect: KAPI_EFFECT_MODIFY_STATE | KAPI_EFFECT_ALLOC_MEMORY, process memory, Locks pages into physical memory, preventing swapping, reversible=yes I hope the really long lines starting here aren't the intended way to go...:) > * side-effect: KAPI_EFFECT_MODIFY_STATE, mm->locked_vm, Increases process locked memory counter, reversible=yes > * side-effect: KAPI_EFFECT_ALLOC_MEMORY, physical pages, May allocate and populate page table entries, condition=Pages not already present, reversible=yes > * side-effect: KAPI_EFFECT_MODIFY_STATE | KAPI_EFFECT_ALLOC_MEMORY, page faults, Triggers page faults to bring pages into memory, condition=Pages not already resident > * side-effect: KAPI_EFFECT_MODIFY_STATE, VMA splitting, May split existing VMAs at lock boundaries, condition=Lock range partially overlaps existing VMA > * state-trans: memory pages, swappable, locked in RAM, Pages become non-swappable and pinned in physical memory > * state-trans: VMA flags, unlocked, VM_LOCKED set, Virtual memory area marked as locked > * capability: CAP_IPC_LOCK, KAPI_CAP_BYPASS_CHECK, CAP_IPC_LOCK capability > * capability-allows: Lock unlimited amount of memory (no RLIMIT_MEMLOCK enforcement) > * capability-without: Must respect RLIMIT_MEMLOCK resource limit > * capability-condition: Checked when RLIMIT_MEMLOCK is 0 or locking would exceed limit > * capability-priority: 0 > * constraint: RLIMIT_MEMLOCK Resource Limit, The RLIMIT_MEMLOCK soft resource limit specifies the maximum bytes of memory that may be locked into RAM. Unprivileged processes are restricted to this limit. CAP_IPC_LOCK capability allows bypassing this limit entirely. The limit is enforced per-process, not per-user. > * constraint-expr: RLIMIT_MEMLOCK Resource Limit, locked_memory + request_size <= RLIMIT_MEMLOCK || CAP_IPC_LOCK > * constraint: Memory Pressure and OOM, Locking large amounts of memory can cause system-wide memory pressure and potentially trigger the OOM killer. The kernel does not prevent locking memory that would destabilize the system. > * constraint: Special Memory Areas, Some memory types cannot be locked or are silently skipped: VM_IO/VM_PFNMAP areas (device mappings) are skipped; Hugetlb pages are inherently pinned and skipped; DAX mappings are always present in memory and skipped; Secret memory (memfd_secret) mappings are skipped; VM_DROPPABLE memory cannot be locked and is skipped; Gate VMA (kernel entry point) is skipped; VM_LOCKED areas are already locked. These special areas are silently excluded without error. > * > * Context: Process context. May sleep. Takes mmap_lock for write. > * > * Return: 0 on success, negative error code on failure Both of these, of course, are much less informative versions of the data you have put up above; it would be nice to unify them somehow. Thanks, jon
