root/include/linux/shm.h

INCLUDED FROM

DEFINITIONS

1. do_shmat
2. is_file_shm_hugepages
3. exit_shm
4. shm_init_task

#ifndef _LINUX_SHM_H_
#define _LINUX_SHM_H_

#include <linux/list.h>
#include <asm/page.h>
#include <uapi/linux/shm.h>
#include <asm/shmparam.h>

struct shmid_kernel /* private to the kernel */
{       
        struct kern_ipc_perm    shm_perm;
        struct file             *shm_file;
        unsigned long           shm_nattch;
        unsigned long           shm_segsz;
        time_t                  shm_atim;
        time_t                  shm_dtim;
        time_t                  shm_ctim;
        pid_t                   shm_cprid;
        pid_t                   shm_lprid;
        struct user_struct      *mlock_user;

        /* The task created the shm object.  NULL if the task is dead. */
        struct task_struct      *shm_creator;
        struct list_head        shm_clist;      /* list by creator */
};

/* shm_mode upper byte flags */
#define SHM_DEST        01000   /* segment will be destroyed on last detach */
#define SHM_LOCKED      02000   /* segment will not be swapped */
#define SHM_HUGETLB     04000   /* segment will use huge TLB pages */
#define SHM_NORESERVE   010000  /* don't check for reservations */

/* Bits [26:31] are reserved */

/*
 * When SHM_HUGETLB is set bits [26:31] encode the log2 of the huge page size.
 * This gives us 6 bits, which is enough until someone invents 128 bit address
 * spaces.
 *
 * Assume these are all power of twos.
 * When 0 use the default page size.
 */
#define SHM_HUGE_SHIFT  26
#define SHM_HUGE_MASK   0x3f
#define SHM_HUGE_2MB    (21 << SHM_HUGE_SHIFT)
#define SHM_HUGE_1GB    (30 << SHM_HUGE_SHIFT)

#ifdef CONFIG_SYSVIPC
struct sysv_shm {
        struct list_head shm_clist;
};

long do_shmat(int shmid, char __user *shmaddr, int shmflg, unsigned long *addr,
              unsigned long shmlba);
int is_file_shm_hugepages(struct file *file);
void exit_shm(struct task_struct *task);
#define shm_init_task(task) INIT_LIST_HEAD(&(task)->sysvshm.shm_clist)
#else
struct sysv_shm {
        /* empty */
};

static inline long do_shmat(int shmid, char __user *shmaddr,
                            int shmflg, unsigned long *addr,
                            unsigned long shmlba)
{
        return -ENOSYS;
}
static inline int is_file_shm_hugepages(struct file *file)
{
        return 0;
}
static inline void exit_shm(struct task_struct *task)
{
}
static inline void shm_init_task(struct task_struct *task)
{
}
#endif

#endif /* _LINUX_SHM_H_ */