Since Linux 3.11, O_TMPFILE flag can be used in open syscall to create
an unnamed file in a directory. The file occupies space in the
filesystem, and can be given a name using linkat syscall. If the file is
closed without being given a name, its contents are deleted.
See the manpage open(2) in Linux for details.
Exports O_TMPFILE for Linux in 386 and amd64 (other architectures
already had it). Exports Linkat syscall and AT_SYMLINK_FOLLOW (used for
giving a name to the file) for all Linux in all architectures.
Fixesgolang/go#7830.
Change-Id: Ib82e44f405b227e227b9cbf317c2657b32e046f5
Reviewed-on: https://go-review.googlesource.com/21003
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
arm64 doesn't have a Dup2 syscall, instead Dup3 is supposed
to be used. Since Dup3 is linux-specific, provide a wrapper
to make writing portable code easier.
Updates golang/go#10235
To verify it, added a testcase for Dup and Dup2.
Change-Id: I066bb60d62b2bd64d7ba0fdfbb334ce2213c78e9
Reviewed-on: https://go-review.googlesource.com/20178
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Riku Voipio <riku.voipio@linaro.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This system call is used to reassociate the current thread with a Linux
namespace (e.g. a network namespace or a mount namespace). This system
call is key to interacting with the primitives enabling Linux containers.
The users of this system call will most likely want to wrap their calls
with a pair of LockOSThread / UnlockOSThread calls. Here is an example
that is a reasonably close approximation of the `ns_exec' program given
as an example in `man 2 setns':
package main
import (
"log"
"os"
"os/exec"
"runtime"
"golang.org/x/sys/unix"
)
func main() {
if len(os.Args) < 3 {
log.Fatalf("%s /proc/PID/ns/FILE cmd args...", os.Args[0])
}
fd, err := unix.Open(os.Args[1], unix.O_RDONLY, 0)
if err != nil {
log.Fatalf("open: %s", err)
}
runtime.LockOSThread()
defer runtime.UnlockOSThread()
if err = unix.Setns(fd, 0); err != nil {
log.Fatalf("setns: %s", err)
}
cmd := exec.Command(os.Args[2], os.Args[3:]...)
cmd.Stdin = os.Stdin
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
err = cmd.Run()
if err != nil {
log.Fatalf("exec: %s", err)
}
}
Fixesgolang/go#5968.
Change-Id: I78dc54667cfaef4f9e99a08d48f6e423686f1b22
Reviewed-on: https://go-review.googlesource.com/20054
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
