unix: add Sysv shared memory support

Initial support added for Darwin, other platforms to be added next

unix/syscall_darwin.go

@@ -433,6 +433,11 @@ func SysctlKinfoProcSlice(name string) ([]KinfoProc, error) {
 
 //sys	sendfile(infd int, outfd int, offset int64, len *int64, hdtr unsafe.Pointer, flags int) (err error)
 
+//sys	shmat(id int, addr uintptr, flag int) (ret uintptr, err error)
+//sys	shmctl(id int, cmd int, buf *SysvShmDesc) (result int, err error)
+//sys	shmdt(addr uintptr) (err error)
+//sys	shmget(key int, size int, flag int) (id int, err error)
+
 /*
  * Exposed directly
  */
@@ -590,10 +595,6 @@ func SysctlKinfoProcSlice(name string) ([]KinfoProc, error) {
 // Msgget
 // Msgsnd
 // Msgrcv
-// Shmat
-// Shmctl
-// Shmdt
-// Shmget
 // Shm_open
 // Shm_unlink
 // Sem_open

unix/syscall_unix.go

@@ -433,3 +433,53 @@ func Lutimes(path string, tv []Timeval) error {
 	}
 	return UtimesNanoAt(AT_FDCWD, path, ts, AT_SYMLINK_NOFOLLOW)
 }
+
+// SysvShmAttach attaches the Sysv shared memory segment associated with the
+// shared memory identifier id.
+func SysvShmAttach(id int, addr uintptr, flag int) ([]byte, error) {
+	addr, errno := shmat(id, addr, flag)
+	if errno != nil {
+		return nil, errno
+	}
+
+	// Retrieve the size of the shared memory to enable slice creation
+	var info SysvShmDesc
+
+	_, err := SysvShmCtl(id, IPC_STAT, &info)
+	if err != nil {
+		// release the shared memory if we can't find the size; ignoring error
+		// here since there's nothing sensible we can return here
+		shmdt(addr)
+		return nil, err
+	}
+
+	// Use unsafe to convert addr into a []byte.
+	var b []byte
+	hdr := (*unsafeheader.Slice)(unsafe.Pointer(&b))
+	hdr.Data = unsafe.Pointer(addr)
+	hdr.Cap = int(info.Segsz)
+	hdr.Len = int(info.Segsz)
+	return b, nil
+}
+
+// SysvShmCtl performs control operations on the shared memory segment
+// specified by id.
+func SysvShmCtl(id, cmd int, desc *SysvShmDesc) (result int, err error) {
+	return shmctl(id, cmd, desc)
+}
+
+// SysvShmDetach unmaps the shared memory slice returned from SysvShmAttach.
+//
+// It is not safe to use the slice after calling this function.
+func SysvShmDetach(data []byte) error {
+	if data == nil {
+		return EINVAL
+	}
+
+	return shmdt(uintptr(unsafe.Pointer(&data[0])))
+}
+
+// SysvShmGet returns the Sysv shared memory identifier associated with key.
+func SysvShmGet(key, size, flag int) (id int, err error) {
+	return shmget(key, size, flag)
+}

unix/syscall_unix_test.go

@@ -852,6 +852,56 @@ func TestRenameat(t *testing.T) {
 	}
 }
 
+func TestSysvSharedMemory(t *testing.T) {
+	// create ipc
+	id, err := unix.SysvShmGet(unix.IPC_PRIVATE, 1024, unix.IPC_CREAT|unix.IPC_EXCL|0o600)
+	if err != nil {
+		t.Fatalf("SysvShmGet: %v", err)
+	}
+	defer func() {
+		_, err := unix.SysvShmCtl(id, unix.IPC_RMID, nil)
+		if err != nil {
+			t.Errorf("Remove failed: %v", err)
+		}
+	}()
+
+	// attach
+	b1, err := unix.SysvShmAttach(id, 0, 0)
+	if err != nil {
+		t.Fatalf("Attach: %v", err)
+	}
+
+	if len(b1) != 1024 {
+		t.Fatalf("b1 len = %v, want 1024", len(b1))
+	}
+
+	b1[42] = 'x'
+
+	// attach again
+	b2, err := unix.SysvShmAttach(id, 0, 0)
+	if err != nil {
+		t.Fatalf("Attach: %v", err)
+	}
+
+	if len(b2) != 1024 {
+		t.Fatalf("b2 len = %v, want 1024", len(b1))
+	}
+
+	b2[43] = 'y'
+	if b2[42] != 'x' || b1[43] != 'y' {
+		t.Fatalf("shared memory isn't shared")
+	}
+
+	// detach
+	if err = unix.SysvShmDetach(b2); err != nil {
+		t.Fatalf("Detach: %v", err)
+	}
+
+	if b1[42] != 'x' || b1[43] != 'y' {
+		t.Fatalf("shared memory was invalidated")
+	}
+}
+
 func TestUtimesNanoAt(t *testing.T) {
 	defer chtmpdir(t)()
 

unix/types_darwin.go

@@ -27,6 +27,7 @@ package unix
 #include <mach/mach.h>
 #include <mach/message.h>
 #include <sys/event.h>
+#include <sys/ipc.h>
 #include <sys/kern_control.h>
 #include <sys/mman.h>
 #include <sys/mount.h>
@@ -34,6 +35,7 @@ package unix
 #include <sys/ptrace.h>
 #include <sys/resource.h>
 #include <sys/select.h>
+#include <sys/shm.h>
 #include <sys/signal.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
@@ -323,3 +325,26 @@ type Vmspace C.struct_vmspace
 type Pcred C.struct__pcred
 
 type Ucred C.struct__ucred
+
+// shm
+
+type SysvIpcPerm C.struct_ipc_perm
+type SysvShmDesc C.struct_shmid_ds
+
+const (
+	IPC_CREAT   = C.IPC_CREAT
+	IPC_EXCL    = C.IPC_EXCL
+	IPC_NOWAIT  = C.IPC_NOWAIT
+	IPC_PRIVATE = C.IPC_PRIVATE
+)
+
+const (
+	IPC_RMID = C.IPC_RMID
+	IPC_SET  = C.IPC_SET
+	IPC_STAT = C.IPC_STAT
+)
+
+const (
+	SHM_RDONLY = C.SHM_RDONLY
+	SHM_RND    = C.SHM_RND
+)

unix/zsyscall_darwin_amd64.go

@@ -734,6 +734,65 @@ var libc_sendfile_trampoline_addr uintptr
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func shmat(id int, addr uintptr, flag int) (ret uintptr, err error) {
+	r0, _, e1 := syscall_syscall(libc_shmat_trampoline_addr, uintptr(id), uintptr(addr), uintptr(flag))
+	ret = uintptr(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+var libc_shmat_trampoline_addr uintptr
+
+//go:cgo_import_dynamic libc_shmat shmat "/usr/lib/libSystem.B.dylib"
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
+func shmctl(id int, cmd int, buf *SysvShmDesc) (result int, err error) {
+	r0, _, e1 := syscall_syscall(libc_shmctl_trampoline_addr, uintptr(id), uintptr(cmd), uintptr(unsafe.Pointer(buf)))
+	result = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+var libc_shmctl_trampoline_addr uintptr
+
+//go:cgo_import_dynamic libc_shmctl shmctl "/usr/lib/libSystem.B.dylib"
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
+func shmdt(addr uintptr) (err error) {
+	_, _, e1 := syscall_syscall(libc_shmdt_trampoline_addr, uintptr(addr), 0, 0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+var libc_shmdt_trampoline_addr uintptr
+
+//go:cgo_import_dynamic libc_shmdt shmdt "/usr/lib/libSystem.B.dylib"
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
+func shmget(key int, size int, flag int) (id int, err error) {
+	r0, _, e1 := syscall_syscall(libc_shmget_trampoline_addr, uintptr(key), uintptr(size), uintptr(flag))
+	id = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+var libc_shmget_trampoline_addr uintptr
+
+//go:cgo_import_dynamic libc_shmget shmget "/usr/lib/libSystem.B.dylib"
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Access(path string, mode uint32) (err error) {
 	var _p0 *byte
 	_p0, err = BytePtrFromString(path)

unix/zsyscall_darwin_amd64.s

@@ -264,6 +264,30 @@ TEXT libc_sendfile_trampoline<>(SB),NOSPLIT,$0-0
 GLOBL	·libc_sendfile_trampoline_addr(SB), RODATA, $8
 DATA	·libc_sendfile_trampoline_addr(SB)/8, $libc_sendfile_trampoline<>(SB)
 
+TEXT libc_shmat_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	libc_shmat(SB)
+
+GLOBL	·libc_shmat_trampoline_addr(SB), RODATA, $8
+DATA	·libc_shmat_trampoline_addr(SB)/8, $libc_shmat_trampoline<>(SB)
+
+TEXT libc_shmctl_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	libc_shmctl(SB)
+
+GLOBL	·libc_shmctl_trampoline_addr(SB), RODATA, $8
+DATA	·libc_shmctl_trampoline_addr(SB)/8, $libc_shmctl_trampoline<>(SB)
+
+TEXT libc_shmdt_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	libc_shmdt(SB)
+
+GLOBL	·libc_shmdt_trampoline_addr(SB), RODATA, $8
+DATA	·libc_shmdt_trampoline_addr(SB)/8, $libc_shmdt_trampoline<>(SB)
+
+TEXT libc_shmget_trampoline<>(SB),NOSPLIT,$0-0
+	JMP	libc_shmget(SB)
+
+GLOBL	·libc_shmget_trampoline_addr(SB), RODATA, $8
+DATA	·libc_shmget_trampoline_addr(SB)/8, $libc_shmget_trampoline<>(SB)
+
 TEXT libc_access_trampoline<>(SB),NOSPLIT,$0-0
 	JMP	libc_access(SB)
 

unix/ztypes_darwin_amd64.go

@@ -639,3 +639,38 @@ type Ucred struct {
 	Ngroups int16
 	Groups  [16]uint32
 }
+type SysvIpcPerm struct {
+	Uid  uint32
+	Gid  uint32
+	Cuid uint32
+	Cgid uint32
+	Mode uint16
+	_    uint16
+	_    int32
+}
+type SysvShmDesc struct {
+	Perm   SysvIpcPerm
+	Segsz  uint64
+	Lpid   int32
+	Cpid   int32
+	Nattch uint16
+	_      [34]byte
+}
+
+const (
+	IPC_CREAT   = 0x200
+	IPC_EXCL    = 0x400
+	IPC_NOWAIT  = 0x800
+	IPC_PRIVATE = 0x0
+)
+
+const (
+	IPC_RMID = 0x0
+	IPC_SET  = 0x1
+	IPC_STAT = 0x2
+)
+
+const (
+	SHM_RDONLY = 0x1000
+	SHM_RND    = 0x2000
+)