L4Re – L4 Runtime Environment

Coarse grained memory allocation, in C.

* (c) 2009 Adam Lackorzynski <adam@os.inf.tu-dresden.de>
* economic rights: Technische Universität Dresden (Germany)
* This file is part of TUD:OS and distributed under the terms of the
* GNU General Public License 2.
* Please see the COPYING-GPL-2 file for details.
#include <l4/re/c/rm.h>
#include <l4/sys/err.h>
#include <stdio.h>
#include <string.h>
static int allocate_mem(unsigned long size_in_bytes, unsigned long flags,
void **virt_addr)
int r;
/* Allocate a free capability index for our data space */
return -L4_ENOMEM;
size_in_bytes = l4_trunc_page(size_in_bytes);
/* Allocate memory via a dataspace */
if ((r = l4re_ma_alloc(size_in_bytes, ds, flags)))
return r;
/* Make the dataspace visible in our address space */
*virt_addr = 0;
if ((r = l4re_rm_attach(virt_addr, size_in_bytes,
/* Free dataspace again */
return r;
/* Done, virtual address is in virt_addr */
return 0;
static int free_mem(void *virt_addr)
int r;
/* Detach memory from our address space */
if ((r = l4re_rm_detach_ds(virt_addr, &ds)))
return r;
/* Free memory at our memory allocator */
/* All went ok */
return 0;
int main(void)
void *virt;
/* Allocate memory: 16k Bytes (usually) */
if (allocate_mem(4 * L4_PAGESIZE, 0, &virt))
return 1;
printf("Allocated memory.\n");
/* Do something with the memory */
memset(virt, 0x12, 4 * L4_PAGESIZE);
printf("Touched memory.\n");
/* Free memory */
if (free_mem(virt))
return 2;
printf("Freed and done. Bye.\n");
return 0;
Size of a large page, log2-based.
Definition: consts.h:42
#define L4_PAGESHIFT
Size of a page, log2-based.
Definition: consts.h:37
Capability allocator C interface.
Error codes.
l4_cap_idx_t l4re_ds_t
Dataspace type.
Definition: dataspace.h:39
long l4re_ma_alloc(long size, l4re_ds_t const mem, unsigned long flags) L4_NOTHROW
Allocate memory.
Definition: mem_alloc.h:192
int l4re_rm_attach(void **start, unsigned long size, l4re_rm_flags_t flags, l4re_ds_t mem, l4re_rm_offset_t offs, unsigned char align) L4_NOTHROW
Definition: rm.h:267
int l4re_rm_detach_ds(void *addr, l4re_ds_t *ds) L4_NOTHROW
Detach, unmap and return affected dataspace in current task.
Definition: rm.h:290
Search for a suitable address range.
Definition: rm.h:68
void l4re_util_cap_free_um(l4_cap_idx_t cap) L4_NOTHROW
Return capability index to capability allocator, and unmaps the object.
l4_cap_idx_t l4re_util_cap_alloc(void) L4_NOTHROW
Get free capability index at capability allocator.
unsigned l4_is_invalid_cap(l4_cap_idx_t c) L4_NOTHROW
Test if a capability selector is the invalid capability.
Definition: types.h:392
No memory.
Definition: err.h:50
l4_addr_t l4_trunc_page(l4_addr_t address) L4_NOTHROW
Round an address down to the next lower page boundary.
Definition: consts.h:364
#define L4_PAGESIZE
Minimal page size (in bytes).
Definition: consts.h:307
Memory allocator C interface.
Region map interface, C interface.