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/mem_alloc>
#include <l4/re/rm>
#include <l4/re/env>
#include <l4/re/dataspace>
#include <l4/sys/err.h>
#include <cstdio>
#include <cstring>
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 */
if (!d.is_valid())
return -L4_ENOMEM;
size_in_bytes = l4_trunc_page(size_in_bytes);
/* Allocate memory via a dataspace */
if ((r = L4Re::Env::env()->mem_alloc()->alloc(size_in_bytes, d, flags)))
return r;
/* Make the dataspace visible in our address space */
*virt_addr = 0;
if ((r = L4Re::Env::env()->rm()->attach(virt_addr, size_in_bytes,
L4Re::Rm::F::Search_addr | L4Re::Rm::F::RW,
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::Env::env()->rm()->detach(virt_addr, &ds)))
return r;
/* Release and return capability slot to 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
Interface for memory-like objects.
Definition: dataspace:63
static Env const * env() noexcept
Returns the initial environment for the current task.
Definition: env:103
@ Super_pages
Allocate super pages.
Definition: mem_alloc:75
L4::Cap< void > alloc() noexcept
Allocate a new capability slot.
bool free(L4::Cap< void > cap, l4_cap_idx_t task=L4_INVALID_CAP, unsigned unmap_flags=L4_FP_ALL_SPACES) noexcept
Free the capability.
bool is_valid() const noexcept
Test whether the capability is a valid capability index (i.e., not L4_INVALID_CAP).
Definition: capability.h:60
Dataspace interface.
Environment interface.
Error codes.
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 interface.
_Cap_alloc & cap_alloc
Capability allocator.
Cap< T > make_cap_rw(L4::Cap< T > cap) noexcept
Make an L4::Ipc::Cap<T> for the given capability with L4_CAP_FPAGE_RW rights.
Definition: ipc_types:634
Region mapper interface.
@ Search_addr
Search for a suitable address range.
Definition: rm:105
Capability allocator.