unix: convert openbsd/386 to direct libc calls

The current code has continued to work on OpenBSD, since it has been using
syscall(2) via libc. However, the system call numbers are still hardcoded in
golang.org/sys/unix. Various system call changes have been made in OpenBSD,
resulting in changes to the system call numbers and arguments, which now
fail when this package is used.

Switch to calling various system calls directly via libc, rather than calling
via libc using syscall(2).

Updates golang/go#36435

Change-Id: Ib42d5415ef35c7f7b9cbc55adaf7ca15973ab287
Reviewed-on: https://go-review.googlesource.com/c/sys/+/421798
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>

unix/mkall.sh

@@ -142,10 +142,10 @@ netbsd_arm64)
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
 	;;
 openbsd_386)
+	mkasm="go run mkasm.go"
 	mkerrors="$mkerrors -m32"
-	mksyscall="go run mksyscall.go -l32 -openbsd"
+	mksyscall="go run mksyscall.go -l32 -openbsd -libc"
 	mksysctl="go run mksysctl_openbsd.go"
-	mksysnum="go run mksysnum.go 'https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/kern/syscalls.master'"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
 	;;
 openbsd_amd64)

unix/syscall_openbsd_libc.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build (openbsd && amd64) || (openbsd && arm64)
-// +build openbsd,amd64 openbsd,arm64
+//go:build (openbsd && 386) || (openbsd && amd64) || (openbsd && arm64)
+// +build openbsd,386 openbsd,amd64 openbsd,arm64
 
 package unix
 
@@ -12,10 +12,16 @@ import _ "unsafe"
 // Implemented in the runtime package (runtime/sys_openbsd3.go)
 func syscall_syscall(fn, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
 func syscall_syscall6(fn, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
+func syscall_syscall10(fn, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10 uintptr) (r1, r2 uintptr, err Errno)
 func syscall_rawSyscall(fn, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
 func syscall_rawSyscall6(fn, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
 
 //go:linkname syscall_syscall syscall.syscall
 //go:linkname syscall_syscall6 syscall.syscall6
+//go:linkname syscall_syscall10 syscall.syscall10
 //go:linkname syscall_rawSyscall syscall.rawSyscall
 //go:linkname syscall_rawSyscall6 syscall.rawSyscall6
+
+func syscall_syscall9(fn, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2 uintptr, err Errno) {
+	return syscall_syscall10(fn, a1, a2, a3, a4, a5, a6, a7, a8, a9, 0)
+}