From a9e3760b0838299649c0d57cca44daaf40ba3c33 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 14 Sep 2026 22:12:34 -1000 Subject: sched_ext: Maintain an online cid mask in the scheduler arena Schedulers on the default cid mapping treat [0, nr_online_cids) as the online set and restart on hotplug. Schedulers that install their own mapping with scx_bpf_cid_override() have no way to learn which cids are online: the count no longer identifies members and the CPU-form cpumask is unusable from cid programs. This is an obvious hole in the cid API. Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's arena, allocated alongside the per-CPU scratch masks and populated after the cid mapping is finalized and before ops.init(), for child schedulers too. The pointer stays valid through ops.exit() with no reference to take. It is the arena offset as a void pointer, the same form struct_ops arena arguments arrive in. The verifier types the void return as a scalar for the program's arena cast. The mask follows the SCX hotplug notifications: seeded from cpu_active_mask and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask only inside a hotplug transition. Updates walk the scheduler list under the lock that also serializes unlinking. Reads are live, not atomic snapshots. Root initialization excludes hotplug. v2: Reworded the getter kerneldoc (Andrea Righi). Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- ipc/msgutil.c | 192 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 192 insertions(+) create mode 100644 ipc/msgutil.c (limited to 'ipc/msgutil.c') diff --git a/ipc/msgutil.c b/ipc/msgutil.c new file mode 100644 index 000000000..e28f0cecb --- /dev/null +++ b/ipc/msgutil.c @@ -0,0 +1,192 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * linux/ipc/msgutil.c + * Copyright (C) 1999, 2004 Manfred Spraul + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "util.h" + +DEFINE_SPINLOCK(mq_lock); + +/* + * The next 2 defines are here bc this is the only file + * compiled when either CONFIG_SYSVIPC and CONFIG_POSIX_MQUEUE + * and not CONFIG_IPC_NS. + */ +struct ipc_namespace init_ipc_ns = { + .ns = NS_COMMON_INIT(init_ipc_ns), + .user_ns = &init_user_ns, +}; + +struct msg_msgseg { + struct msg_msgseg *next; + /* the next part of the message follows immediately */ +}; + +#define DATALEN_MSG ((size_t)PAGE_SIZE-sizeof(struct msg_msg)) +#define DATALEN_SEG ((size_t)PAGE_SIZE-sizeof(struct msg_msgseg)) + +static kmem_buckets *msg_buckets __ro_after_init; + +static int __init init_msg_buckets(void) +{ + msg_buckets = kmem_buckets_create("msg_msg", SLAB_ACCOUNT, + sizeof(struct msg_msg), + DATALEN_MSG, NULL); + + return 0; +} +subsys_initcall(init_msg_buckets); + +static struct msg_msg *alloc_msg(size_t len) +{ + struct msg_msg *msg; + struct msg_msgseg **pseg; + size_t alen; + + alen = min(len, DATALEN_MSG); + msg = kmem_buckets_alloc(msg_buckets, sizeof(*msg) + alen, GFP_KERNEL); + if (msg == NULL) + return NULL; + + msg->next = NULL; + msg->security = NULL; + + len -= alen; + pseg = &msg->next; + while (len > 0) { + struct msg_msgseg *seg; + + cond_resched(); + + alen = min(len, DATALEN_SEG); + seg = kmalloc(sizeof(*seg) + alen, GFP_KERNEL_ACCOUNT); + if (seg == NULL) + goto out_err; + *pseg = seg; + seg->next = NULL; + pseg = &seg->next; + len -= alen; + } + + return msg; + +out_err: + free_msg(msg); + return NULL; +} + +struct msg_msg *load_msg(const void __user *src, size_t len) +{ + struct msg_msg *msg; + struct msg_msgseg *seg; + int err = -EFAULT; + size_t alen; + + msg = alloc_msg(len); + if (msg == NULL) + return ERR_PTR(-ENOMEM); + + alen = min(len, DATALEN_MSG); + if (copy_from_user(msg + 1, src, alen)) + goto out_err; + + for (seg = msg->next; seg != NULL; seg = seg->next) { + len -= alen; + src = (char __user *)src + alen; + alen = min(len, DATALEN_SEG); + if (copy_from_user(seg + 1, src, alen)) + goto out_err; + } + + err = security_msg_msg_alloc(msg); + if (err) + goto out_err; + + return msg; + +out_err: + free_msg(msg); + return ERR_PTR(err); +} +#ifdef CONFIG_CHECKPOINT_RESTORE +struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst) +{ + struct msg_msgseg *dst_pseg, *src_pseg; + size_t len = src->m_ts; + size_t alen; + + if (src->m_ts > dst->m_ts) + return ERR_PTR(-EINVAL); + + alen = min(len, DATALEN_MSG); + memcpy(dst + 1, src + 1, alen); + + for (dst_pseg = dst->next, src_pseg = src->next; + src_pseg != NULL; + dst_pseg = dst_pseg->next, src_pseg = src_pseg->next) { + + len -= alen; + alen = min(len, DATALEN_SEG); + memcpy(dst_pseg + 1, src_pseg + 1, alen); + } + + dst->m_type = src->m_type; + dst->m_ts = src->m_ts; + + return dst; +} +#else +struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst) +{ + return ERR_PTR(-ENOSYS); +} +#endif +int store_msg(void __user *dest, struct msg_msg *msg, size_t len) +{ + size_t alen; + struct msg_msgseg *seg; + + alen = min(len, DATALEN_MSG); + if (copy_to_user(dest, msg + 1, alen)) + return -1; + + for (seg = msg->next; seg != NULL; seg = seg->next) { + len -= alen; + dest = (char __user *)dest + alen; + alen = min(len, DATALEN_SEG); + if (copy_to_user(dest, seg + 1, alen)) + return -1; + } + return 0; +} + +void free_msg(struct msg_msg *msg) +{ + struct msg_msgseg *seg; + + security_msg_msg_free(msg); + + seg = msg->next; + kfree(msg); + while (seg != NULL) { + struct msg_msgseg *tmp = seg->next; + + cond_resched(); + kfree(seg); + seg = tmp; + } +} -- cgit v1.3.1