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author | jhb <jhb@FreeBSD.org> | 2008-01-08 21:58:16 +0000 |
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committer | jhb <jhb@FreeBSD.org> | 2008-01-08 21:58:16 +0000 |
commit | 8cd9437636744162d1427275b2fe66cf8ccef25c (patch) | |
tree | 49b07dc757aae71e0a64eb4939cde4037af60a24 /sys/compat/freebsd32 | |
parent | 23d78439c96372baa4a3c2847df65f8e11455ae7 (diff) | |
download | FreeBSD-src-8cd9437636744162d1427275b2fe66cf8ccef25c.zip FreeBSD-src-8cd9437636744162d1427275b2fe66cf8ccef25c.tar.gz |
Add a new file descriptor type for IPC shared memory objects and use it to
implement shm_open(2) and shm_unlink(2) in the kernel:
- Each shared memory file descriptor is associated with a swap-backed vm
object which provides the backing store. Each descriptor starts off with
a size of zero, but the size can be altered via ftruncate(2). The shared
memory file descriptors also support fstat(2). read(2), write(2),
ioctl(2), select(2), poll(2), and kevent(2) are not supported on shared
memory file descriptors.
- shm_open(2) and shm_unlink(2) are now implemented as system calls that
manage shared memory file descriptors. The virtual namespace that maps
pathnames to shared memory file descriptors is implemented as a hash
table where the hash key is generated via the 32-bit Fowler/Noll/Vo hash
of the pathname.
- As an extension, the constant 'SHM_ANON' may be specified in place of the
path argument to shm_open(2). In this case, an unnamed shared memory
file descriptor will be created similar to the IPC_PRIVATE key for
shmget(2). Note that the shared memory object can still be shared among
processes by sharing the file descriptor via fork(2) or sendmsg(2), but
it is unnamed. This effectively serves to implement the getmemfd() idea
bandied about the lists several times over the years.
- The backing store for shared memory file descriptors are garbage
collected when they are not referenced by any open file descriptors or
the shm_open(2) virtual namespace.
Submitted by: dillon, peter (previous versions)
Submitted by: rwatson (I based this on his version)
Reviewed by: alc (suggested converting getmemfd() to shm_open())
Diffstat (limited to 'sys/compat/freebsd32')
-rw-r--r-- | sys/compat/freebsd32/syscalls.master | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/sys/compat/freebsd32/syscalls.master b/sys/compat/freebsd32/syscalls.master index 04c86f7..923ab26 100644 --- a/sys/compat/freebsd32/syscalls.master +++ b/sys/compat/freebsd32/syscalls.master @@ -796,3 +796,6 @@ 480 AUE_FTRUNCATE STD { int freebsd32_ftruncate(int fd, \ u_int32_t lengthlo, u_int32_t lengthhi); } 481 AUE_KILL NOPROTO { int thr_kill2(pid_t pid, long id, int sig); } +482 AUE_NULL NOPROTO { int shm_open(const char *path, int flags, \ + mode_t mode); } +483 AUE_NULL NOPROTO { int shm_unlink(const char *path); } |