[release-branch.go1.19] syscall, internal/poll: fall back to accept on linux-arm

src/internal/poll/sock_cloexec.go

@@ -5,7 +5,7 @@
 // This file implements accept for platforms that provide a fast path for
 // setting SetNonblock and CloseOnExec.
 
-//go:build dragonfly || freebsd || linux || netbsd || openbsd || solaris
+//go:build dragonfly || freebsd || (linux && !arm) || netbsd || openbsd || solaris
 
 package poll
 

src/internal/poll/sock_cloexec_accept.go

@@ -0,0 +1,51 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements accept for platforms that provide a fast path for
+// setting SetNonblock and CloseOnExec, but don't necessarily have accept4.
+// This is the code we used for accept in Go 1.17 and earlier.
+// On Linux the accept4 system call was introduced in 2.6.28 kernel,
+// and our minimum requirement is 2.6.32, so we simplified the function.
+// Unfortunately, on ARM accept4 wasn't added until 2.6.36, so for ARM
+// only we continue using the older code.
+
+//go:build linux && arm
+
+package poll
+
+import "syscall"
+
+// Wrapper around the accept system call that marks the returned file
+// descriptor as nonblocking and close-on-exec.
+func accept(s int) (int, syscall.Sockaddr, string, error) {
+	ns, sa, err := Accept4Func(s, syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC)
+	switch err {
+	case nil:
+		return ns, sa, "", nil
+	default: // errors other than the ones listed
+		return -1, sa, "accept4", err
+	case syscall.ENOSYS: // syscall missing
+	case syscall.EINVAL: // some Linux use this instead of ENOSYS
+	case syscall.EACCES: // some Linux use this instead of ENOSYS
+	case syscall.EFAULT: // some Linux use this instead of ENOSYS
+	}
+
+	// See ../syscall/exec_unix.go for description of ForkLock.
+	// It is probably okay to hold the lock across syscall.Accept
+	// because we have put fd.sysfd into non-blocking mode.
+	// However, a call to the File method will put it back into
+	// blocking mode. We can't take that risk, so no use of ForkLock here.
+	ns, sa, err = AcceptFunc(s)
+	if err == nil {
+		syscall.CloseOnExec(ns)
+	}
+	if err != nil {
+		return -1, nil, "accept", err
+	}
+	if err = syscall.SetNonblock(ns, true); err != nil {
+		CloseFunc(ns)
+		return -1, nil, "setnonblock", err
+	}
+	return ns, sa, "", nil
+}

src/syscall/syscall_linux.go

@@ -630,21 +630,6 @@ func anyToSockaddr(rsa *RawSockaddrAny) (Sockaddr, error) {
 	return nil, EAFNOSUPPORT
 }
 
-func Accept(fd int) (nfd int, sa Sockaddr, err error) {
-	var rsa RawSockaddrAny
-	var len _Socklen = SizeofSockaddrAny
-	nfd, err = accept4(fd, &rsa, &len, 0)
-	if err != nil {
-		return
-	}
-	sa, err = anyToSockaddr(&rsa)
-	if err != nil {
-		Close(nfd)
-		nfd = 0
-	}
-	return
-}
-
 func Accept4(fd int, flags int) (nfd int, sa Sockaddr, err error) {
 	var rsa RawSockaddrAny
 	var len _Socklen = SizeofSockaddrAny

src/syscall/syscall_linux_accept.go

@@ -0,0 +1,34 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// We require Linux kernel version 2.6.32. The accept4 system call was
+// added in version 2.6.28, so in general we can use accept4.
+// Unfortunately, for ARM only, accept4 was added in version 2.6.36.
+// Handle that case here, by using a copy of the Accept function that
+// we used in Go 1.17.
+
+//go:build linux && arm
+
+package syscall
+
+//sys	accept(s int, rsa *RawSockaddrAny, addrlen *_Socklen) (fd int, err error)
+
+func Accept(fd int) (nfd int, sa Sockaddr, err error) {
+	var rsa RawSockaddrAny
+	var len _Socklen = SizeofSockaddrAny
+	// Try accept4 first for Android and newer kernels.
+	nfd, err = accept4(fd, &rsa, &len, 0)
+	if err == ENOSYS {
+		nfd, err = accept(fd, &rsa, &len)
+	}
+	if err != nil {
+		return
+	}
+	sa, err = anyToSockaddr(&rsa)
+	if err != nil {
+		Close(nfd)
+		nfd = 0
+	}
+	return
+}

src/syscall/syscall_linux_accept4.go

@@ -0,0 +1,25 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file provides the Accept function used on all systems
+// other than arm. See syscall_linux_accept.go for why.
+
+//go:build linux && !arm
+
+package syscall
+
+func Accept(fd int) (nfd int, sa Sockaddr, err error) {
+	var rsa RawSockaddrAny
+	var len _Socklen = SizeofSockaddrAny
+	nfd, err = accept4(fd, &rsa, &len, 0)
+	if err != nil {
+		return
+	}
+	sa, err = anyToSockaddr(&rsa)
+	if err != nil {
+		Close(nfd)
+		nfd = 0
+	}
+	return
+}