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// 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_RANDOM = 25 // introduced in 2.6.29
)
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))
for i := 0; 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:
// Check that the true physical page size is
// compatible with the runtime's assumed
// physical page size.
if sys.PhysPageSize < val {
print("runtime: kernel page size (", val, ") is larger than runtime page size (", sys.PhysPageSize, ")\n")
exit(1)
}
if sys.PhysPageSize%val != 0 {
print("runtime: runtime page size (", sys.PhysPageSize, ") is not a multiple of kernel page size (", val, ")\n")
exit(1)
}
}
// Commented out for gccgo for now.
// archauxv(tag, val)
}
}
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