Implement shm object table

[lttng-ust.git] / libringbuffer / shm.h

#ifndef _LIBRINGBUFFER_SHM_H
#define _LIBRINGBUFFER_SHM_H

/*
 * libringbuffer/shm.h
 *
 * Copyright 2011 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * Dual LGPL v2.1/GPL v2 license.
 */

#include <stdint.h>
#include <ust/usterr-signal-safe.h>
#include "ust/core.h"
#include "shm_types.h"

#define SHM_MAGIC	0x54335433
#define SHM_MAJOR	0
#define SHM_MINOR	1

/*
 * Pointer dereferencing. We don't trust the shm_ref, so we validate
 * both the index and offset with known boundaries.
 */
static inline
char *_shmp(struct shm_object_table *table, struct shm_ref *ref)
{
	struct shm_object *obj;
	size_t index, offset;

	index = (size_t) ref->index;
	if (unlikely(index >= table->allocated_len))
		return NULL;
	obj = &table->objects[index];
	offset = (size_t) ref->offset;
	if (unlikely(offset >= obj->memory_map_size))
		return NULL;
	return &obj->memory_map[offset];
}

#define shmp(handle, ref)						\
	({								\
		__typeof__((ref)._type) ____ptr_ret;			\
		____ptr_ret = (__typeof__(____ptr_ret)) _shmp((handle)->table, &(ref)._ref);	\
		____ptr_ret;						\
	})

static inline
void _set_shmp(struct shm_ref *ref, struct shm_ref src)
{
	*ref = src;
}

#define set_shmp(ref, src)	_set_shmp(&(ref)._ref, src)

struct shm_object_table *shm_object_table_create(size_t max_nb_obj);
void shm_object_table_destroy(struct shm_object_table *table);
struct shm_object *shm_object_table_append(struct shm_object_table *table,
					   size_t memory_map_size);

/*
 * zalloc_shm - allocate memory within a shm object.
 *
 * Shared memory is already zeroed by shmget.
 * *NOT* multithread-safe (should be protected by mutex).
 * Returns a -1, -1 tuple on error.
 */
struct shm_ref zalloc_shm(struct shm_object *obj, size_t len);
void align_shm(struct shm_object *obj, size_t align);

#endif /* _LIBRINGBUFFER_SHM_H */