1 files changed, 171 insertions, 0 deletions
diff --git a/libgo/go/runtime/os_linux.go b/libgo/go/runtime/os_linux.go
new file mode 100644
index 0000000000..ad334869ed
--- /dev/null
+++ b/libgo/go/runtime/os_linux.go
@@ -0,0 +1,171 @@
+// 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.
+
+package runtime
+
+import (
+	"runtime/internal/sys"
+	"unsafe"
+)
+
+type mOS struct {
+	unused byte
+}
+
+func futex(addr unsafe.Pointer, op int32, val uint32, ts, addr2 unsafe.Pointer, val3 uint32) int32 {
+	return int32(syscall(_SYS_futex, uintptr(addr), uintptr(op), uintptr(val), uintptr(ts), uintptr(addr2), uintptr(val3)))
+}
+
+// Linux futex.
+//
+//	futexsleep(uint32 *addr, uint32 val)
+//	futexwakeup(uint32 *addr)
+//
+// Futexsleep atomically checks if *addr == val and if so, sleeps on addr.
+// Futexwakeup wakes up threads sleeping on addr.
+// Futexsleep is allowed to wake up spuriously.
+
+const (
+	_FUTEX_WAIT = 0
+	_FUTEX_WAKE = 1
+)
+
+// Atomically,
+//	if(*addr == val) sleep
+// Might be woken up spuriously; that's allowed.
+// Don't sleep longer than ns; ns < 0 means forever.
+//go:nosplit
+func futexsleep(addr *uint32, val uint32, ns int64) {
+	var ts timespec
+
+	// Some Linux kernels have a bug where futex of
+	// FUTEX_WAIT returns an internal error code
+	// as an errno. Libpthread ignores the return value
+	// here, and so can we: as it says a few lines up,
+	// spurious wakeups are allowed.
+	if ns < 0 {
+		futex(unsafe.Pointer(addr), _FUTEX_WAIT, val, nil, nil, 0)
+		return
+	}
+
+	// It's difficult to live within the no-split stack limits here.
+	// On ARM and 386, a 64-bit divide invokes a general software routine
+	// that needs more stack than we can afford. So we use timediv instead.
+	// But on real 64-bit systems, where words are larger but the stack limit
+	// is not, even timediv is too heavy, and we really need to use just an
+	// ordinary machine instruction.
+	if sys.PtrSize == 8 {
+		ts.set_sec(ns / 1000000000)
+		ts.set_nsec(int32(ns % 1000000000))
+	} else {
+		ts.tv_nsec = 0
+		ts.set_sec(int64(timediv(ns, 1000000000, (*int32)(unsafe.Pointer(&ts.tv_nsec)))))
+	}
+	futex(unsafe.Pointer(addr), _FUTEX_WAIT, val, unsafe.Pointer(&ts), nil, 0)
+}
+
+// If any procs are sleeping on addr, wake up at most cnt.
+//go:nosplit
+func futexwakeup(addr *uint32, cnt uint32) {
+	ret := futex(unsafe.Pointer(addr), _FUTEX_WAKE, cnt, nil, nil, 0)
+	if ret >= 0 {
+		return
+	}
+
+	// I don't know that futex wakeup can return
+	// EAGAIN or EINTR, but if it does, it would be
+	// safe to loop and call futex again.
+	systemstack(func() {
+		print("futexwakeup addr=", addr, " returned ", ret, "\n")
+	})
+
+	*(*int32)(unsafe.Pointer(uintptr(0x1006))) = 0x1006
+}
+
+const (
+	_AT_NULL   = 0  // End of vector
+	_AT_PAGESZ = 6  // System physical page size
+	_AT_HWCAP  = 16 // hardware capability bit vector
+	_AT_RANDOM = 25 // introduced in 2.6.29
+	_AT_HWCAP2 = 26 // hardware capability bit vector 2
+)
+
+var procAuxv = []byte("/proc/self/auxv\x00")
+
+func sysargs(argc int32, argv **byte) {
+	n := argc + 1
+
+	// skip over argv, envp to get to auxv
+	for argv_index(argv, n) != nil {
+		n++
+	}
+
+	// skip NULL separator
+	n++
+
+	// now argv+n is auxv
+	auxv := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*sys.PtrSize))
+	if sysauxv(auxv[:]) == 0 {
+		// In some situations we don't get a loader-provided
+		// auxv, such as when loaded as a library on Android.
+		// Fall back to /proc/self/auxv.
+		fd := open(&procAuxv[0], 0 /* O_RDONLY */, 0)
+		if fd < 0 {
+			// On Android, /proc/self/auxv might be unreadable (issue 9229), so we fallback to
+			// try using mincore to detect the physical page size.
+			// mincore should return EINVAL when address is not a multiple of system page size.
+			const size = 256 << 10 // size of memory region to allocate
+			p := mmap(nil, size, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
+			if uintptr(p) < 4096 {
+				return
+			}
+			var n uintptr
+			for n = 4 << 10; n < size; n <<= 1 {
+				err := mincore(unsafe.Pointer(uintptr(p)+n), 1, &addrspace_vec[0])
+				if err == 0 {
+					physPageSize = n
+					break
+				}
+			}
+			if physPageSize == 0 {
+				physPageSize = size
+			}
+			munmap(p, size)
+			return
+		}
+		var buf [128]uintptr
+		n := read(fd, noescape(unsafe.Pointer(&buf[0])), int32(unsafe.Sizeof(buf)))
+		closefd(fd)
+		if n < 0 {
+			return
+		}
+		// Make sure buf is terminated, even if we didn't read
+		// the whole file.
+		buf[len(buf)-2] = _AT_NULL
+		sysauxv(buf[:])
+	}
+}
+
+func sysauxv(auxv []uintptr) int {
+	var i int
+	for ; auxv[i] != _AT_NULL; i += 2 {
+		tag, val := auxv[i], auxv[i+1]
+		switch tag {
+		case _AT_RANDOM:
+			// The kernel provides a pointer to 16-bytes
+			// worth of random data.
+			startupRandomData = (*[16]byte)(unsafe.Pointer(val))[:]
+
+		case _AT_PAGESZ:
+			physPageSize = val
+		}
+
+		// Commented out for gccgo for now.
+		// archauxv(tag, val)
+	}
+	return i / 2
+}
+
+// Temporary for gccgo until we port mem_GOOS.go.
+var addrspace_vec [1]byte