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package container
import (
. "syscall"
"unsafe"
"hakurei.app/container/std"
)
// Prctl manipulates various aspects of the behavior of the calling thread or process.
func Prctl(op, arg2, arg3 uintptr) error {
r, _, errno := Syscall(SYS_PRCTL, op, arg2, arg3)
if r < 0 {
return errno
}
return nil
}
// SetPtracer allows processes to ptrace(2) the calling process.
func SetPtracer(pid uintptr) error { return Prctl(PR_SET_PTRACER, pid, 0) }
// linux/sched/coredump.h
const (
SUID_DUMP_DISABLE = iota
SUID_DUMP_USER
)
// SetDumpable sets the "dumpable" attribute of the calling process.
func SetDumpable(dumpable uintptr) error { return Prctl(PR_SET_DUMPABLE, dumpable, 0) }
// SetNoNewPrivs sets the calling thread's no_new_privs attribute.
func SetNoNewPrivs() error { return Prctl(PR_SET_NO_NEW_PRIVS, 1, 0) }
// Isatty tests whether a file descriptor refers to a terminal.
func Isatty(fd int) bool {
var buf [8]byte
r, _, _ := Syscall(
SYS_IOCTL,
uintptr(fd),
TIOCGWINSZ,
uintptr(unsafe.Pointer(&buf[0])),
)
return r == 0
}
// schedParam is equivalent to struct sched_param from include/linux/sched.h.
type schedParam struct {
// sched_priority
priority std.Int
}
// schedSetscheduler sets both the scheduling policy and parameters for the
// thread whose ID is specified in tid. If tid equals zero, the scheduling
// policy and parameters of the calling thread will be set.
//
// This function is unexported because it is [very subtle to use correctly]. The
// function signature in libc is misleading: pid actually refers to a thread ID.
// The glibc wrapper for this system call ignores this semantic and exposes
// this counterintuitive behaviour.
//
// This function is only called from the container setup thread. Do not reuse
// this if you do not have something similar in place!
//
// [very subtle to use correctly]: https://www.openwall.com/lists/musl/2016/03/01/4
func schedSetscheduler(tid int, policy std.SchedPolicy, param *schedParam) error {
if r, _, errno := Syscall(
SYS_SCHED_SETSCHEDULER,
uintptr(tid),
uintptr(policy),
uintptr(unsafe.Pointer(param)),
); r < 0 {
return errno
}
return nil
}
// IgnoringEINTR makes a function call and repeats it if it returns an
// EINTR error. This appears to be required even though we install all
// signal handlers with SA_RESTART: see #22838, #38033, #38836, #40846.
// Also #20400 and #36644 are issues in which a signal handler is
// installed without setting SA_RESTART. None of these are the common case,
// but there are enough of them that it seems that we can't avoid
// an EINTR loop.
func IgnoringEINTR(fn func() error) error {
for {
err := fn()
if err != EINTR {
return err
}
}
}
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