L4Re – L4 Runtime Environment

Sharing memory between applications, client side.

* (c) 2009 Adam Lackorzynski <adam@os.inf.tu-dresden.de>,
* Alexander Warg <warg@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/util/cap_alloc> // L4::Cap
#include <l4/re/dataspace> // L4Re::Dataspace
#include <l4/re/rm> // L4::Rm
#include <l4/re/env> // L4::Env
#include <l4/sys/cache.h>
#include <cstring>
#include <cstdio>
#include <unistd.h>
#include "interface.h"
int main()
* Try to get server interface cap.
L4::Cap<My_interface> svr = L4Re::Env::env()->get_cap<My_interface>("shm");
if (!svr.is_valid())
printf("Could not get the server capability\n");
return 1;
* Alloc data space cap slot
if (!ds.is_valid())
printf("Could not get capability slot!\n");
return 1;
* Alloc server notifier IRQ cap slot
if (!irq.is_valid())
printf("Could not get capability slot!\n");
return 1;
* Request shared data-space cap.
if (svr->get_shared_buffer(ds, irq))
printf("Could not get shared memory dataspace!\n");
return 1;
* Attach to arbitrary region
char *addr = 0;
int err = L4Re::Env::env()->rm()->attach(&addr, ds->size(),
L4Re::Rm::F::Search_addr | L4Re::Rm::F::RW,
if (err < 0)
printf("Error attaching data space: %s\n", l4sys_errtostr(err));
return 1;
printf("Content: %s\n", addr);
// wait a bit for the demo effect
printf("Sleeping a bit...\n");
* Fill in new stuff
memset(addr, 0, ds->size());
char const * const msg = "Hello from client, too!";
printf("Setting new content in shared memory\n");
snprintf(addr, strlen(msg)+1, msg);
l4_cache_clean_data((unsigned long)addr,
(unsigned long)addr + strlen(msg) + 1);
// notify the server
* Detach region containing addr, result should be Detached_ds (other results
* only apply if we split regions etc.).
err = L4Re::Env::env()->rm()->detach(addr, 0);
if (err)
printf("Failed to detach region\n");
/* Free objects and capabilties, just for completeness. */
L4Re::Util::cap_alloc.free(ds, L4Re::This_task);
L4Re::Util::cap_alloc.free(irq, L4Re::This_task);
return 0;
Interface for memory-like objects.
Definition: dataspace:63
Size size() const noexcept
Get size of a dataspace.
static Env const * env() noexcept
Returns the initial environment for the current task.
Definition: env:103
L4::Cap< Rm > rm() const noexcept
Object-capability to the region map.
Definition: env:127
L4::Cap< T > get_cap(char const *name, unsigned l) const noexcept
Get the capability selector for the object named name.
Definition: env:204
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
C++ interface for capabilities.
Definition: capability.h:219
C++ Irq interface.
Definition: irq:118
Dataspace interface.
Environment interface.
int l4_cache_clean_data(unsigned long start, unsigned long end) L4_NOTHROW
Cache clean a range in D-cache.
Definition: cache.h:81
_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
l4_msgtag_t trigger(l4_utcb_t *utcb=l4_utcb()) noexcept
Definition: irq:93
Capability allocator.