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Diffstat (limited to 'ipc/util.c')
| -rw-r--r-- | ipc/util.c | 580 |
1 files changed, 580 insertions, 0 deletions
diff --git a/ipc/util.c b/ipc/util.c new file mode 100644 index 000000000000..e00c35f7b2b8 --- /dev/null +++ b/ipc/util.c @@ -0,0 +1,580 @@ +/* + * linux/ipc/util.c + * Copyright (C) 1992 Krishna Balasubramanian + * + * Sep 1997 - Call suser() last after "normal" permission checks so we + * get BSD style process accounting right. + * Occurs in several places in the IPC code. + * Chris Evans, <chris@ferret.lmh.ox.ac.uk> + * Nov 1999 - ipc helper functions, unified SMP locking + * Manfred Spraul <manfreds@colorfullife.com> + * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary(). + * Mingming Cao <cmm@us.ibm.com> + */ + +#include <linux/config.h> +#include <linux/mm.h> +#include <linux/shm.h> +#include <linux/init.h> +#include <linux/msg.h> +#include <linux/smp_lock.h> +#include <linux/vmalloc.h> +#include <linux/slab.h> +#include <linux/highuid.h> +#include <linux/security.h> +#include <linux/rcupdate.h> +#include <linux/workqueue.h> + +#include <asm/unistd.h> + +#include "util.h" + +/** + * ipc_init - initialise IPC subsystem + * + * The various system5 IPC resources (semaphores, messages and shared + * memory are initialised + */ + +static int __init ipc_init(void) +{ + sem_init(); + msg_init(); + shm_init(); + return 0; +} +__initcall(ipc_init); + +/** + * ipc_init_ids - initialise IPC identifiers + * @ids: Identifier set + * @size: Number of identifiers + * + * Given a size for the ipc identifier range (limited below IPCMNI) + * set up the sequence range to use then allocate and initialise the + * array itself. + */ + +void __init ipc_init_ids(struct ipc_ids* ids, int size) +{ + int i; + sema_init(&ids->sem,1); + + if(size > IPCMNI) + size = IPCMNI; + ids->in_use = 0; + ids->max_id = -1; + ids->seq = 0; + { + int seq_limit = INT_MAX/SEQ_MULTIPLIER; + if(seq_limit > USHRT_MAX) + ids->seq_max = USHRT_MAX; + else + ids->seq_max = seq_limit; + } + + ids->entries = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*size + + sizeof(struct ipc_id_ary)); + + if(ids->entries == NULL) { + printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n"); + size = 0; + ids->entries = &ids->nullentry; + } + ids->entries->size = size; + for(i=0;i<size;i++) + ids->entries->p[i] = NULL; +} + +/** + * ipc_findkey - find a key in an ipc identifier set + * @ids: Identifier set + * @key: The key to find + * + * Requires ipc_ids.sem locked. + * Returns the identifier if found or -1 if not. + */ + +int ipc_findkey(struct ipc_ids* ids, key_t key) +{ + int id; + struct kern_ipc_perm* p; + int max_id = ids->max_id; + + /* + * rcu_dereference() is not needed here + * since ipc_ids.sem is held + */ + for (id = 0; id <= max_id; id++) { + p = ids->entries->p[id]; + if(p==NULL) + continue; + if (key == p->key) + return id; + } + return -1; +} + +/* + * Requires ipc_ids.sem locked + */ +static int grow_ary(struct ipc_ids* ids, int newsize) +{ + struct ipc_id_ary* new; + struct ipc_id_ary* old; + int i; + int size = ids->entries->size; + + if(newsize > IPCMNI) + newsize = IPCMNI; + if(newsize <= size) + return newsize; + + new = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*newsize + + sizeof(struct ipc_id_ary)); + if(new == NULL) + return size; + new->size = newsize; + memcpy(new->p, ids->entries->p, sizeof(struct kern_ipc_perm *)*size + + sizeof(struct ipc_id_ary)); + for(i=size;i<newsize;i++) { + new->p[i] = NULL; + } + old = ids->entries; + + /* + * Use rcu_assign_pointer() to make sure the memcpyed contents + * of the new array are visible before the new array becomes visible. + */ + rcu_assign_pointer(ids->entries, new); + + ipc_rcu_putref(old); + return newsize; +} + +/** + * ipc_addid - add an IPC identifier + * @ids: IPC identifier set + * @new: new IPC permission set + * @size: new size limit for the id array + * + * Add an entry 'new' to the IPC arrays. The permissions object is + * initialised and the first free entry is set up and the id assigned + * is returned. The list is returned in a locked state on success. + * On failure the list is not locked and -1 is returned. + * + * Called with ipc_ids.sem held. + */ + +int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size) +{ + int id; + + size = grow_ary(ids,size); + + /* + * rcu_dereference()() is not needed here since + * ipc_ids.sem is held + */ + for (id = 0; id < size; id++) { + if(ids->entries->p[id] == NULL) + goto found; + } + return -1; +found: + ids->in_use++; + if (id > ids->max_id) + ids->max_id = id; + + new->cuid = new->uid = current->euid; + new->gid = new->cgid = current->egid; + + new->seq = ids->seq++; + if(ids->seq > ids->seq_max) + ids->seq = 0; + + spin_lock_init(&new->lock); + new->deleted = 0; + rcu_read_lock(); + spin_lock(&new->lock); + ids->entries->p[id] = new; + return id; +} + +/** + * ipc_rmid - remove an IPC identifier + * @ids: identifier set + * @id: Identifier to remove + * + * The identifier must be valid, and in use. The kernel will panic if + * fed an invalid identifier. The entry is removed and internal + * variables recomputed. The object associated with the identifier + * is returned. + * ipc_ids.sem and the spinlock for this ID is hold before this function + * is called, and remain locked on the exit. + */ + +struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id) +{ + struct kern_ipc_perm* p; + int lid = id % SEQ_MULTIPLIER; + if(lid >= ids->entries->size) + BUG(); + + /* + * do not need a rcu_dereference()() here to force ordering + * on Alpha, since the ipc_ids.sem is held. + */ + p = ids->entries->p[lid]; + ids->entries->p[lid] = NULL; + if(p==NULL) + BUG(); + ids->in_use--; + + if (lid == ids->max_id) { + do { + lid--; + if(lid == -1) + break; + } while (ids->entries->p[lid] == NULL); + ids->max_id = lid; + } + p->deleted = 1; + return p; +} + +/** + * ipc_alloc - allocate ipc space + * @size: size desired + * + * Allocate memory from the appropriate pools and return a pointer to it. + * NULL is returned if the allocation fails + */ + +void* ipc_alloc(int size) +{ + void* out; + if(size > PAGE_SIZE) + out = vmalloc(size); + else + out = kmalloc(size, GFP_KERNEL); + return out; +} + +/** + * ipc_free - free ipc space + * @ptr: pointer returned by ipc_alloc + * @size: size of block + * + * Free a block created with ipc_alloc. The caller must know the size + * used in the allocation call. + */ + +void ipc_free(void* ptr, int size) +{ + if(size > PAGE_SIZE) + vfree(ptr); + else + kfree(ptr); +} + +/* + * rcu allocations: + * There are three headers that are prepended to the actual allocation: + * - during use: ipc_rcu_hdr. + * - during the rcu grace period: ipc_rcu_grace. + * - [only if vmalloc]: ipc_rcu_sched. + * Their lifetime doesn't overlap, thus the headers share the same memory. + * Unlike a normal union, they are right-aligned, thus some container_of + * forward/backward casting is necessary: + */ +struct ipc_rcu_hdr +{ + int refcount; + int is_vmalloc; + void *data[0]; +}; + + +struct ipc_rcu_grace +{ + struct rcu_head rcu; + /* "void *" makes sure alignment of following data is sane. */ + void *data[0]; +}; + +struct ipc_rcu_sched +{ + struct work_struct work; + /* "void *" makes sure alignment of following data is sane. */ + void *data[0]; +}; + +#define HDRLEN_KMALLOC (sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \ + sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr)) +#define HDRLEN_VMALLOC (sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \ + sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC) + +static inline int rcu_use_vmalloc(int size) +{ + /* Too big for a single page? */ + if (HDRLEN_KMALLOC + size > PAGE_SIZE) + return 1; + return 0; +} + +/** + * ipc_rcu_alloc - allocate ipc and rcu space + * @size: size desired + * + * Allocate memory for the rcu header structure + the object. + * Returns the pointer to the object. + * NULL is returned if the allocation fails. + */ + +void* ipc_rcu_alloc(int size) +{ + void* out; + /* + * We prepend the allocation with the rcu struct, and + * workqueue if necessary (for vmalloc). + */ + if (rcu_use_vmalloc(size)) { + out = vmalloc(HDRLEN_VMALLOC + size); + if (out) { + out += HDRLEN_VMALLOC; + container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1; + container_of(out, struct ipc_rcu_hdr, data)->refcount = 1; + } + } else { + out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL); + if (out) { + out += HDRLEN_KMALLOC; + container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0; + container_of(out, struct ipc_rcu_hdr, data)->refcount = 1; + } + } + + return out; +} + +void ipc_rcu_getref(void *ptr) +{ + container_of(ptr, struct ipc_rcu_hdr, data)->refcount++; +} + +/** + * ipc_schedule_free - free ipc + rcu space + * + * Since RCU callback function is called in bh, + * we need to defer the vfree to schedule_work + */ +static void ipc_schedule_free(struct rcu_head *head) +{ + struct ipc_rcu_grace *grace = + container_of(head, struct ipc_rcu_grace, rcu); + struct ipc_rcu_sched *sched = + container_of(&(grace->data[0]), struct ipc_rcu_sched, data[0]); + + INIT_WORK(&sched->work, vfree, sched); + schedule_work(&sched->work); +} + +/** + * ipc_immediate_free - free ipc + rcu space + * + * Free from the RCU callback context + * + */ +static void ipc_immediate_free(struct rcu_head *head) +{ + struct ipc_rcu_grace *free = + container_of(head, struct ipc_rcu_grace, rcu); + kfree(free); +} + +void ipc_rcu_putref(void *ptr) +{ + if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0) + return; + + if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) { + call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu, + ipc_schedule_free); + } else { + call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu, + ipc_immediate_free); + } +} + +/** + * ipcperms - check IPC permissions + * @ipcp: IPC permission set + * @flag: desired permission set. + * + * Check user, group, other permissions for access + * to ipc resources. return 0 if allowed + */ + +int ipcperms (struct kern_ipc_perm *ipcp, short flag) +{ /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */ + int requested_mode, granted_mode; + + requested_mode = (flag >> 6) | (flag >> 3) | flag; + granted_mode = ipcp->mode; + if (current->euid == ipcp->cuid || current->euid == ipcp->uid) + granted_mode >>= 6; + else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid)) + granted_mode >>= 3; + /* is there some bit set in requested_mode but not in granted_mode? */ + if ((requested_mode & ~granted_mode & 0007) && + !capable(CAP_IPC_OWNER)) + return -1; + + return security_ipc_permission(ipcp, flag); +} + +/* + * Functions to convert between the kern_ipc_perm structure and the + * old/new ipc_perm structures + */ + +/** + * kernel_to_ipc64_perm - convert kernel ipc permissions to user + * @in: kernel permissions + * @out: new style IPC permissions + * + * Turn the kernel object 'in' into a set of permissions descriptions + * for returning to userspace (out). + */ + + +void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out) +{ + out->key = in->key; + out->uid = in->uid; + out->gid = in->gid; + out->cuid = in->cuid; + out->cgid = in->cgid; + out->mode = in->mode; + out->seq = in->seq; +} + +/** + * ipc64_perm_to_ipc_perm - convert old ipc permissions to new + * @in: new style IPC permissions + * @out: old style IPC permissions + * + * Turn the new style permissions object in into a compatibility + * object and store it into the 'out' pointer. + */ + +void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out) +{ + out->key = in->key; + SET_UID(out->uid, in->uid); + SET_GID(out->gid, in->gid); + SET_UID(out->cuid, in->cuid); + SET_GID(out->cgid, in->cgid); + out->mode = in->mode; + out->seq = in->seq; +} + +/* + * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get() + * is called with shm_ids.sem locked. Since grow_ary() is also called with + * shm_ids.sem down(for Shared Memory), there is no need to add read + * barriers here to gurantee the writes in grow_ary() are seen in order + * here (for Alpha). + * + * However ipc_get() itself does not necessary require ipc_ids.sem down. So + * if in the future ipc_get() is used by other places without ipc_ids.sem + * down, then ipc_get() needs read memery barriers as ipc_lock() does. + */ +struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id) +{ + struct kern_ipc_perm* out; + int lid = id % SEQ_MULTIPLIER; + if(lid >= ids->entries->size) + return NULL; + out = ids->entries->p[lid]; + return out; +} + +struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id) +{ + struct kern_ipc_perm* out; + int lid = id % SEQ_MULTIPLIER; + struct ipc_id_ary* entries; + + rcu_read_lock(); + entries = rcu_dereference(ids->entries); + if(lid >= entries->size) { + rcu_read_unlock(); + return NULL; + } + out = entries->p[lid]; + if(out == NULL) { + rcu_read_unlock(); + return NULL; + } + spin_lock(&out->lock); + + /* ipc_rmid() may have already freed the ID while ipc_lock + * was spinning: here verify that the structure is still valid + */ + if (out->deleted) { + spin_unlock(&out->lock); + rcu_read_unlock(); + return NULL; + } + return out; +} + +void ipc_lock_by_ptr(struct kern_ipc_perm *perm) +{ + rcu_read_lock(); + spin_lock(&perm->lock); +} + +void ipc_unlock(struct kern_ipc_perm* perm) +{ + spin_unlock(&perm->lock); + rcu_read_unlock(); +} + +int ipc_buildid(struct ipc_ids* ids, int id, int seq) +{ + return SEQ_MULTIPLIER*seq + id; +} + +int ipc_checkid(struct ipc_ids* ids, struct kern_ipc_perm* ipcp, int uid) +{ + if(uid/SEQ_MULTIPLIER != ipcp->seq) + return 1; + return 0; +} + +#ifdef __ARCH_WANT_IPC_PARSE_VERSION + + +/** + * ipc_parse_version - IPC call version + * @cmd: pointer to command + * + * Return IPC_64 for new style IPC and IPC_OLD for old style IPC. + * The cmd value is turned from an encoding command and version into + * just the command code. + */ + +int ipc_parse_version (int *cmd) +{ + if (*cmd & IPC_64) { + *cmd ^= IPC_64; + return IPC_64; + } else { + return IPC_OLD; + } +} + +#endif /* __ARCH_WANT_IPC_PARSE_VERSION */ |