unix: add openat2 for linux
openat2 is a new syscall added to Linux 5.6. It provides a superset
of openat(2) functionality, providing a way to extend it in the future,
and (for now) adding flags telling the kernel how to resolve the path.
For more info on openat2, see https://lwn.net/Articles/803237/
A primitive test case is added to check that Openat2 works as
it should. Tested to skip on kernel 5.5 and pass on 5.6.
Change-Id: Ib8bbd71791762f043200543cecdea16d2fd3c81d
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Reviewed-on: https://go-review.googlesource.com/c/sys/+/227280
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
diff --git a/unix/linux/types.go b/unix/linux/types.go
index 1e90b2e..10f1ea4 100644
--- a/unix/linux/types.go
+++ b/unix/linux/types.go
@@ -106,6 +106,7 @@
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter.h>
#include <linux/netlink.h>
+#include <linux/openat2.h>
#include <linux/perf_event.h>
#include <linux/random.h>
#include <linux/rtc.h>
@@ -833,6 +834,18 @@
AT_EACCESS = C.AT_EACCESS
)
+type OpenHow C.struct_open_how
+
+const SizeofOpenHow = C.sizeof_struct_open_how
+
+const (
+ RESOLVE_BENEATH = C.RESOLVE_BENEATH
+ RESOLVE_IN_ROOT = C.RESOLVE_IN_ROOT
+ RESOLVE_NO_MAGICLINKS = C.RESOLVE_NO_MAGICLINKS
+ RESOLVE_NO_SYMLINKS = C.RESOLVE_NO_SYMLINKS
+ RESOLVE_NO_XDEV = C.RESOLVE_NO_XDEV
+)
+
type PollFd C.struct_pollfd
const (
diff --git a/unix/syscall_linux.go b/unix/syscall_linux.go
index bbe1abb..2b151eb 100644
--- a/unix/syscall_linux.go
+++ b/unix/syscall_linux.go
@@ -133,6 +133,12 @@
return openat(dirfd, path, flags|O_LARGEFILE, mode)
}
+//sys openat2(dirfd int, path string, open_how *OpenHow, size int) (fd int, err error)
+
+func Openat2(dirfd int, path string, how *OpenHow) (fd int, err error) {
+ return openat2(dirfd, path, how, SizeofOpenHow)
+}
+
//sys ppoll(fds *PollFd, nfds int, timeout *Timespec, sigmask *Sigset_t) (n int, err error)
func Ppoll(fds []PollFd, timeout *Timespec, sigmask *Sigset_t) (n int, err error) {
diff --git a/unix/syscall_linux_test.go b/unix/syscall_linux_test.go
index e572376..8adb426 100644
--- a/unix/syscall_linux_test.go
+++ b/unix/syscall_linux_test.go
@@ -663,3 +663,24 @@
t.Fatalf("unexpected return from prctl; got %v, expected %v", v, 1)
}
}
+
+func TestOpenat2(t *testing.T) {
+ how := &unix.OpenHow{
+ Flags: unix.O_RDONLY,
+ Resolve: unix.RESOLVE_NO_MAGICLINKS,
+ }
+ fd, err := unix.Openat2(-1, "/proc/self/fd/1", how)
+ switch err {
+ case nil:
+ unix.Close(fd)
+ t.Fatal("expected ELOOP, got nil")
+ case unix.ELOOP:
+ return
+ case unix.ENOSYS:
+ t.Skip("old kernel? (need Linux >= 5.6)")
+ case unix.ENOENT:
+ t.Skipf("openat2: %v, skipping test", err)
+ default:
+ t.Fatalf("unexpected error from openat2: %v", err)
+ }
+}
diff --git a/unix/zsyscall_linux.go b/unix/zsyscall_linux.go
index fd2dae8..5c5b742 100644
--- a/unix/zsyscall_linux.go
+++ b/unix/zsyscall_linux.go
@@ -83,6 +83,22 @@
// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+func openat2(dirfd int, path string, open_how *OpenHow, size int) (fd int, err error) {
+ var _p0 *byte
+ _p0, err = BytePtrFromString(path)
+ if err != nil {
+ return
+ }
+ r0, _, e1 := Syscall6(SYS_OPENAT2, uintptr(dirfd), uintptr(unsafe.Pointer(_p0)), uintptr(unsafe.Pointer(open_how)), uintptr(size), 0, 0)
+ fd = int(r0)
+ if e1 != 0 {
+ err = errnoErr(e1)
+ }
+ return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
func ppoll(fds *PollFd, nfds int, timeout *Timespec, sigmask *Sigset_t) (n int, err error) {
r0, _, e1 := Syscall6(SYS_PPOLL, uintptr(unsafe.Pointer(fds)), uintptr(nfds), uintptr(unsafe.Pointer(timeout)), uintptr(unsafe.Pointer(sigmask)), 0, 0)
n = int(r0)
diff --git a/unix/ztypes_linux.go b/unix/ztypes_linux.go
index 9c43c26..781a5ea 100644
--- a/unix/ztypes_linux.go
+++ b/unix/ztypes_linux.go
@@ -691,6 +691,22 @@
AT_EACCESS = 0x200
)
+type OpenHow struct {
+ Flags uint64
+ Mode uint64
+ Resolve uint64
+}
+
+const SizeofOpenHow = 0x18
+
+const (
+ RESOLVE_BENEATH = 0x8
+ RESOLVE_IN_ROOT = 0x10
+ RESOLVE_NO_MAGICLINKS = 0x2
+ RESOLVE_NO_SYMLINKS = 0x4
+ RESOLVE_NO_XDEV = 0x1
+)
+
type PollFd struct {
Fd int32
Events int16
