ext: move syscall wrappers from container

These are generally useful, and none of them are container-specific. Syscalls subtle to use and requiring container-specific setup remains in container.

Signed-off-by: Ophestra <cat@gensokyo.uk>

5 files changed, 17 insertions, 59 deletions

diff --git a/container/capability.go b/container/capability.go
index 3ea9d028..1d98ec4b 100644
--- a/container/capability.go
+++ b/container/capability.go
@@ -3,6 +3,8 @@ package container
 import (
 	"syscall"
 	"unsafe"
+
+	"hakurei.app/ext"
 )
 
 const (
@@ -51,15 +53,15 @@ func capset(hdrp *capHeader, datap *[2]capData) error {
 
 // capBoundingSetDrop drops a capability from the calling thread's capability bounding set.
 func capBoundingSetDrop(cap uintptr) error {
-	return Prctl(syscall.PR_CAPBSET_DROP, cap, 0)
+	return ext.Prctl(syscall.PR_CAPBSET_DROP, cap, 0)
 }
 
 // capAmbientClearAll clears the ambient capability set of the calling thread.
 func capAmbientClearAll() error {
-	return Prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0)
+	return ext.Prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0)
 }
 
 // capAmbientRaise adds to the ambient capability set of the calling thread.
 func capAmbientRaise(cap uintptr) error {
-	return Prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap)
+	return ext.Prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap)
 }
diff --git a/container/dispatcher.go b/container/dispatcher.go
index 710e4392..dce5f023 100644
--- a/container/dispatcher.go
+++ b/container/dispatcher.go
@@ -13,6 +13,7 @@ import (
 
 	"hakurei.app/container/seccomp"
 	"hakurei.app/container/std"
+	"hakurei.app/ext"
 	"hakurei.app/internal/netlink"
 	"hakurei.app/message"
 )
@@ -143,8 +144,8 @@ func (k direct) new(f func(k syscallDispatcher)) { go f(k) }
 
 func (direct) lockOSThread() { runtime.LockOSThread() }
 
-func (direct) setPtracer(pid uintptr) error       { return SetPtracer(pid) }
-func (direct) setDumpable(dumpable uintptr) error { return SetDumpable(dumpable) }
+func (direct) setPtracer(pid uintptr) error       { return ext.SetPtracer(pid) }
+func (direct) setDumpable(dumpable uintptr) error { return ext.SetDumpable(dumpable) }
 func (direct) setNoNewPrivs() error               { return SetNoNewPrivs() }
 
 func (direct) lastcap(msg message.Msg) uintptr                 { return LastCap(msg) }
@@ -152,7 +153,7 @@ func (direct) capset(hdrp *capHeader, datap *[2]capData) error { return capset(h
 func (direct) capBoundingSetDrop(cap uintptr) error            { return capBoundingSetDrop(cap) }
 func (direct) capAmbientClearAll() error                       { return capAmbientClearAll() }
 func (direct) capAmbientRaise(cap uintptr) error               { return capAmbientRaise(cap) }
-func (direct) isatty(fd int) bool                              { return Isatty(fd) }
+func (direct) isatty(fd int) bool                              { return ext.Isatty(fd) }
 func (direct) receive(key string, e any, fdp *uintptr) (func() error, error) {
 	return Receive(key, e, fdp)
 }
diff --git a/container/init.go b/container/init.go
index 8fbf757e..3e2ec809 100644
--- a/container/init.go
+++ b/container/init.go
@@ -17,6 +17,7 @@ import (
 
 	"hakurei.app/container/fhs"
 	"hakurei.app/container/seccomp"
+	"hakurei.app/ext"
 	"hakurei.app/message"
 )
 
@@ -178,7 +179,7 @@ func initEntrypoint(k syscallDispatcher, msg message.Msg) {
 	}
 
 	// write uid/gid map here so parent does not need to set dumpable
-	if err := k.setDumpable(SUID_DUMP_USER); err != nil {
+	if err := k.setDumpable(ext.SUID_DUMP_USER); err != nil {
 		k.fatalf(msg, "cannot set SUID_DUMP_USER: %v", err)
 	}
 	if err := k.writeFile(fhs.Proc+"self/uid_map",
@@ -196,7 +197,7 @@ func initEntrypoint(k syscallDispatcher, msg message.Msg) {
 		0); err != nil {
 		k.fatalf(msg, "%v", err)
 	}
-	if err := k.setDumpable(SUID_DUMP_DISABLE); err != nil {
+	if err := k.setDumpable(ext.SUID_DUMP_DISABLE); err != nil {
 		k.fatalf(msg, "cannot set SUID_DUMP_DISABLE: %v", err)
 	}
 
@@ -290,7 +291,7 @@ func initEntrypoint(k syscallDispatcher, msg message.Msg) {
 
 	{
 		var fd int
-		if err := IgnoringEINTR(func() (err error) {
+		if err := ext.IgnoringEINTR(func() (err error) {
 			fd, err = k.open(fhs.Root, O_DIRECTORY|O_RDONLY, 0)
 			return
 		}); err != nil {
diff --git a/container/mount.go b/container/mount.go
index 171b210b..f6a8844f 100644
--- a/container/mount.go
+++ b/container/mount.go
@@ -6,6 +6,7 @@ import (
 	"os"
 	. "syscall"
 
+	"hakurei.app/ext"
 	"hakurei.app/message"
 	"hakurei.app/vfs"
 )
@@ -115,7 +116,7 @@ func (p *procPaths) remount(msg message.Msg, target string, flags uintptr) error
 	var targetKFinal string
 	{
 		var destFd int
-		if err := IgnoringEINTR(func() (err error) {
+		if err := ext.IgnoringEINTR(func() (err error) {
 			destFd, err = p.k.open(targetFinal, O_PATH|O_CLOEXEC, 0)
 			return
 		}); err != nil {
diff --git a/container/syscall.go b/container/syscall.go
index f5c634b0..c71e298c 100644
--- a/container/syscall.go
+++ b/container/syscall.go
@@ -7,40 +7,9 @@ import (
 	"hakurei.app/ext"
 )
 
-// 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
+func SetNoNewPrivs() error {
+	return ext.Prctl(PR_SET_NO_NEW_PRIVS, 1, 0)
 }
 
 // schedParam is equivalent to struct sched_param from include/linux/sched.h.
@@ -73,19 +42,3 @@ func schedSetscheduler(tid int, policy ext.SchedPolicy, param *schedParam) error
 	}
 	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
-		}
-	}
-}