#include
#include
#include
#include
#include
#include
#include
#include
#include
#if defined(CONFIG_SYSVIPC)
#include "util.h"
struct ipc_ids {
int size;
int in_use;
int max_id;
unsigned short seq;
unsigned short seq_max;
struct semaphore sem;
spinlock_t ary;
struct ipc_id* entries;
};
struct ipc_id {
struct kern_ipc_perm* p;
};
/**
* 初始化ipc子系统
*
* The various system5 IPC resources (semaphores, messages and shared
* memory are initialised
*/
void __init ipc_init (void)
{
sem_init();
msg_init();
shm_init();
return;
}
/**
初始化ipc标识
*
* 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);
//限定size大小不超过IPCMNI
if(size > IPCMNI)
size = IPCMNI;
ids->size = size;
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;
}
//分配size大小的struct ipc_id空间
ids->entries = ipc_alloc(sizeof(struct ipc_id)*size);
if(ids->entries == NULL) {
printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
ids->size = 0;
}
ids->ary = SPIN_LOCK_UNLOCKED;
//初始化entries指针
for(i=0;isize;i++)
ids->entries[i].p = NULL;
}
/**
* 在ipc标识集中查找键值为key的ipc标识
*
* 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;
for (id = 0; id <= ids->max_id; id++) {
p = ids->entries[id].p;
if(p==NULL)
continue;
if (key == p->key)
return id;
}
return -1;
}
static int grow_ary(struct ipc_ids* ids, int newsize)
{
struct ipc_id* new;
struct ipc_id* old;
int i;
//限定newsize大小不超过IPCMNI
if(newsize > IPCMNI)
newsize = IPCMNI;
if(newsize <= ids->size)
return newsize;
//分配newsize大小的struct ipc_id空间
new = ipc_alloc(sizeof(struct ipc_id)*newsize);
if(new == NULL)
return ids->size;
memcpy(new, ids->entries, sizeof(struct ipc_id)*ids->size);
for(i=ids->size;i new[i].p = NULL;
}
spin_lock(&ids->ary);
old = ids->entries;
ids->entries = new;
i = ids->size;
ids->size = newsize;
spin_unlock(&ids->ary);
//回收原先分配的struct ipc_id空间
ipc_free(old, sizeof(struct ipc_id)*i);
return ids->size;
}
/**
在ipc标识集中添加一个新标识符
*
* 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.
*/
int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
{
int id;
size = grow_ary(ids,size);
//依次查找,直到发现第一个非空项
for (id = 0; id < size; id++) {
if(ids->entries[id].p == 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(&ids->ary);
ids->entries[id].p = new;
return id;
}
/**
从ipc标识集中删除一个标识符
* 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.
*/
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->size)
BUG();
p = ids->entries[lid].p;
ids->entries[lid].p = NULL;
if(p==NULL)
BUG();
ids->in_use--;
if (lid == ids->max_id) {
do {
lid--;
if(lid == -1)
break;
} while (ids->entries[lid].p == NULL);
ids->max_id = lid;
}
return p;
}
/**
分配size大小的空间
* 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;
}
/**
释放ptr指向的空间
*
* 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);
}
/**
查看ipc访问权限
* 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 */
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 0;
}
/**
转换struct kern_ipc_perm数据到用户空间
*
* 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;
}
/**
转换struct ipc64_perm数据到struct ipc_perm
* 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;
out->uid = NEW_TO_OLD_UID(in->uid);
out->gid = NEW_TO_OLD_GID(in->gid);
out->cuid = NEW_TO_OLD_UID(in->cuid);
out->cgid = NEW_TO_OLD_GID(in->cgid);
out->mode = in->mode;
out->seq = in->seq;
}
#endif /* CONFIG_SYSVIPC */
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