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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"
)
// 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
}
func getproccount() int32 {
// This buffer is huge (8 kB) but we are on the system stack
// and there should be plenty of space (64 kB).
// Also this is a leaf, so we're not holding up the memory for long.
// See golang.org/issue/11823.
// The suggested behavior here is to keep trying with ever-larger
// buffers, but we don't have a dynamic memory allocator at the
// moment, so that's a bit tricky and seems like overkill.
const maxCPUs = 64 * 1024
var buf [maxCPUs / (sys.PtrSize * 8)]uintptr
r := sched_getaffinity(0, unsafe.Sizeof(buf), &buf[0])
n := int32(0)
for _, v := range buf[:r/sys.PtrSize] {
for v != 0 {
n += int32(v & 1)
v >>= 1
}
}
if n == 0 {
n = 1
}
return n
}
// Clone, the Linux rfork.
const (
_CLONE_VM = 0x100
_CLONE_FS = 0x200
_CLONE_FILES = 0x400
_CLONE_SIGHAND = 0x800
_CLONE_PTRACE = 0x2000
_CLONE_VFORK = 0x4000
_CLONE_PARENT = 0x8000
_CLONE_THREAD = 0x10000
_CLONE_NEWNS = 0x20000
_CLONE_SYSVSEM = 0x40000
_CLONE_SETTLS = 0x80000
_CLONE_PARENT_SETTID = 0x100000
_CLONE_CHILD_CLEARTID = 0x200000
_CLONE_UNTRACED = 0x800000
_CLONE_CHILD_SETTID = 0x1000000
_CLONE_STOPPED = 0x2000000
_CLONE_NEWUTS = 0x4000000
_CLONE_NEWIPC = 0x8000000
cloneFlags = _CLONE_VM | /* share memory */
_CLONE_FS | /* share cwd, etc */
_CLONE_FILES | /* share fd table */
_CLONE_SIGHAND | /* share sig handler table */
_CLONE_THREAD /* revisit - okay for now */
)
// May run with m.p==nil, so write barriers are not allowed.
//go:nowritebarrier
func newosproc(mp *m, stk unsafe.Pointer) {
/*
* note: strace gets confused if we use CLONE_PTRACE here.
*/
if false {
print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " clone=", funcPC(clone), " id=", mp.id, " ostk=", &mp, "\n")
}
// Disable signals during clone, so that the new thread starts
// with signals disabled. It will enable them in minit.
var oset sigset
rtsigprocmask(_SIG_SETMASK, &sigset_all, &oset, int32(unsafe.Sizeof(oset)))
ret := clone(cloneFlags, stk, unsafe.Pointer(mp), unsafe.Pointer(mp.g0), unsafe.Pointer(funcPC(mstart)))
rtsigprocmask(_SIG_SETMASK, &oset, nil, int32(unsafe.Sizeof(oset)))
if ret < 0 {
print("runtime: failed to create new OS thread (have ", mcount(), " already; errno=", -ret, ")\n")
throw("newosproc")
}
}
// Version of newosproc that doesn't require a valid G.
//go:nosplit
func newosproc0(stacksize uintptr, fn unsafe.Pointer) {
stack := sysAlloc(stacksize, &memstats.stacks_sys)
if stack == nil {
write(2, unsafe.Pointer(&failallocatestack[0]), int32(len(failallocatestack)))
exit(1)
}
ret := clone(cloneFlags, unsafe.Pointer(uintptr(stack)+stacksize), nil, nil, fn)
if ret < 0 {
write(2, unsafe.Pointer(&failthreadcreate[0]), int32(len(failthreadcreate)))
exit(1)
}
}
var failallocatestack = []byte("runtime: failed to allocate stack for the new OS thread\n")
var failthreadcreate = []byte("runtime: failed to create new OS thread\n")
func osinit() {
ncpu = getproccount()
}
var urandom_dev = []byte("/dev/urandom\x00")
func getRandomData(r []byte) {
if startupRandomData != nil {
n := copy(r, startupRandomData)
extendRandom(r, n)
return
}
fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
closefd(fd)
extendRandom(r, int(n))
}
func goenvs() {
goenvs_unix()
}
// Called to do synchronous initialization of Go code built with
// -buildmode=c-archive or -buildmode=c-shared.
// None of the Go runtime is initialized.
//go:nosplit
//go:nowritebarrierrec
func libpreinit() {
initsig(true)
}
// Called to initialize a new m (including the bootstrap m).
// Called on the parent thread (main thread in case of bootstrap), can allocate memory.
func mpreinit(mp *m) {
mp.gsignal = malg(32 * 1024) // Linux wants >= 2K
mp.gsignal.m = mp
}
//go:nosplit
func msigsave(mp *m) {
smask := &mp.sigmask
rtsigprocmask(_SIG_SETMASK, nil, smask, int32(unsafe.Sizeof(*smask)))
}
//go:nosplit
func msigrestore(sigmask sigset) {
rtsigprocmask(_SIG_SETMASK, &sigmask, nil, int32(unsafe.Sizeof(sigmask)))
}
//go:nosplit
func sigblock() {
rtsigprocmask(_SIG_SETMASK, &sigset_all, nil, int32(unsafe.Sizeof(sigset_all)))
}
func gettid() uint32
// Called to initialize a new m (including the bootstrap m).
// Called on the new thread, cannot allocate memory.
func minit() {
// Initialize signal handling.
_g_ := getg()
var st sigaltstackt
sigaltstack(nil, &st)
if st.ss_flags&_SS_DISABLE != 0 {
signalstack(&_g_.m.gsignal.stack)
_g_.m.newSigstack = true
} else {
// Use existing signal stack.
stsp := uintptr(unsafe.Pointer(st.ss_sp))
_g_.m.gsignal.stack.lo = stsp
_g_.m.gsignal.stack.hi = stsp + st.ss_size
_g_.m.gsignal.stackguard0 = stsp + _StackGuard
_g_.m.gsignal.stackguard1 = stsp + _StackGuard
_g_.m.gsignal.stackAlloc = st.ss_size
_g_.m.newSigstack = false
}
// for debuggers, in case cgo created the thread
_g_.m.procid = uint64(gettid())
// restore signal mask from m.sigmask and unblock essential signals
nmask := _g_.m.sigmask
for i := range sigtable {
if sigtable[i].flags&_SigUnblock != 0 {
sigdelset(&nmask, i)
}
}
rtsigprocmask(_SIG_SETMASK, &nmask, nil, int32(unsafe.Sizeof(nmask)))
}
// Called from dropm to undo the effect of an minit.
//go:nosplit
func unminit() {
if getg().m.newSigstack {
signalstack(nil)
}
}
func memlimit() uintptr {
/*
TODO: Convert to Go when something actually uses the result.
Rlimit rl;
extern byte runtime·text[], runtime·end[];
uintptr used;
if(runtime·getrlimit(RLIMIT_AS, &rl) != 0)
return 0;
if(rl.rlim_cur >= 0x7fffffff)
return 0;
// Estimate our VM footprint excluding the heap.
// Not an exact science: use size of binary plus
// some room for thread stacks.
used = runtime·end - runtime·text + (64<<20);
if(used >= rl.rlim_cur)
return 0;
// If there's not at least 16 MB left, we're probably
// not going to be able to do much. Treat as no limit.
rl.rlim_cur -= used;
if(rl.rlim_cur < (16<<20))
return 0;
return rl.rlim_cur - used;
*/
return 0
}
//#ifdef GOARCH_386
//#define sa_handler k_sa_handler
//#endif
func sigreturn()
func sigtramp()
func cgoSigtramp()
//go:nosplit
//go:nowritebarrierrec
func setsig(i int32, fn uintptr, restart bool) {
var sa sigactiont
memclr(unsafe.Pointer(&sa), unsafe.Sizeof(sa))
sa.sa_flags = _SA_SIGINFO | _SA_ONSTACK | _SA_RESTORER
if restart {
sa.sa_flags |= _SA_RESTART
}
sigfillset(&sa.sa_mask)
// Although Linux manpage says "sa_restorer element is obsolete and
// should not be used". x86_64 kernel requires it. Only use it on
// x86.
if GOARCH == "386" || GOARCH == "amd64" {
sa.sa_restorer = funcPC(sigreturn)
}
if fn == funcPC(sighandler) {
if iscgo {
fn = funcPC(cgoSigtramp)
} else {
fn = funcPC(sigtramp)
}
}
sa.sa_handler = fn
rt_sigaction(uintptr(i), &sa, nil, unsafe.Sizeof(sa.sa_mask))
}
//go:nosplit
//go:nowritebarrierrec
func setsigstack(i int32) {
var sa sigactiont
if rt_sigaction(uintptr(i), nil, &sa, unsafe.Sizeof(sa.sa_mask)) != 0 {
throw("rt_sigaction failure")
}
if sa.sa_handler == 0 || sa.sa_handler == _SIG_DFL || sa.sa_handler == _SIG_IGN || sa.sa_flags&_SA_ONSTACK != 0 {
return
}
sa.sa_flags |= _SA_ONSTACK
if rt_sigaction(uintptr(i), &sa, nil, unsafe.Sizeof(sa.sa_mask)) != 0 {
throw("rt_sigaction failure")
}
}
//go:nosplit
//go:nowritebarrierrec
func getsig(i int32) uintptr {
var sa sigactiont
memclr(unsafe.Pointer(&sa), unsafe.Sizeof(sa))
if rt_sigaction(uintptr(i), nil, &sa, unsafe.Sizeof(sa.sa_mask)) != 0 {
throw("rt_sigaction read failure")
}
if sa.sa_handler == funcPC(sigtramp) || sa.sa_handler == funcPC(cgoSigtramp) {
return funcPC(sighandler)
}
return sa.sa_handler
}
//go:nosplit
func signalstack(s *stack) {
var st sigaltstackt
if s == nil {
st.ss_flags = _SS_DISABLE
} else {
st.ss_sp = (*byte)(unsafe.Pointer(s.lo))
st.ss_size = s.hi - s.lo
st.ss_flags = 0
}
sigaltstack(&st, nil)
}
//go:nosplit
//go:nowritebarrierrec
func updatesigmask(m sigmask) {
var mask sigset
sigcopyset(&mask, m)
rtsigprocmask(_SIG_SETMASK, &mask, nil, int32(unsafe.Sizeof(mask)))
}
func unblocksig(sig int32) {
var mask sigset
sigaddset(&mask, int(sig))
rtsigprocmask(_SIG_UNBLOCK, &mask, nil, int32(unsafe.Sizeof(mask)))
}