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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{}
//go:noescape
func futex(addr unsafe.Pointer, op int32, val uint32, ts, addr2 unsafe.Pointer, val3 uint32) int32
// 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_PRIVATE_FLAG = 128
_FUTEX_WAIT_PRIVATE = 0 | _FUTEX_PRIVATE_FLAG
_FUTEX_WAKE_PRIVATE = 1 | _FUTEX_PRIVATE_FLAG
)
// 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) {
// 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_PRIVATE, val, nil, nil, 0)
return
}
var ts timespec
ts.setNsec(ns)
futex(unsafe.Pointer(addr), _FUTEX_WAIT_PRIVATE, 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_PRIVATE, 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 / 8]byte
r := sched_getaffinity(0, unsafe.Sizeof(buf), &buf[0])
if r < 0 {
return 1
}
n := int32(0)
for _, v := range buf[:r] {
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
// As of QEMU 2.8.0 (5ea2fc84d), user emulation requires all six of these
// flags to be set when creating a thread; attempts to share the other
// five but leave SYSVSEM unshared will fail with -EINVAL.
//
// In non-QEMU environments CLONE_SYSVSEM is inconsequential as we do not
// use System V semaphores.
cloneFlags = _CLONE_VM | /* share memory */
_CLONE_FS | /* share cwd, etc */
_CLONE_FILES | /* share fd table */
_CLONE_SIGHAND | /* share sig handler table */
_CLONE_SYSVSEM | /* share SysV semaphore undo lists (see issue #20763) */
_CLONE_THREAD /* revisit - okay for now */
)
//go:noescape
func clone(flags int32, stk, mp, gp, fn unsafe.Pointer) int32
// May run with m.p==nil, so write barriers are not allowed.
//go:nowritebarrier
func newosproc(mp *m) {
stk := unsafe.Pointer(mp.g0.stack.hi)
/*
* 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
sigprocmask(_SIG_SETMASK, &sigset_all, &oset)
ret := clone(cloneFlags, stk, unsafe.Pointer(mp), unsafe.Pointer(mp.g0), unsafe.Pointer(funcPC(mstart)))
sigprocmask(_SIG_SETMASK, &oset, nil)
if ret < 0 {
print("runtime: failed to create new OS thread (have ", mcount(), " already; errno=", -ret, ")\n")
if ret == -_EAGAIN {
println("runtime: may need to increase max user processes (ulimit -u)")
}
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")
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")
var addrspace_vec [1]byte
func mincore(addr unsafe.Pointer, n uintptr, dst *byte) int32
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 {
return
}
// 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, err := mmap(nil, size, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
if err != 0 {
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[:])
}
// startupRandomData holds random bytes initialized at startup. These come from
// the ELF AT_RANDOM auxiliary vector.
var startupRandomData []byte
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
}
archauxv(tag, val)
vdsoauxv(tag, val)
}
return i / 2
}
var sysTHPSizePath = []byte("/sys/kernel/mm/transparent_hugepage/hpage_pmd_size\x00")
func getHugePageSize() uintptr {
var numbuf [20]byte
fd := open(&sysTHPSizePath[0], 0 /* O_RDONLY */, 0)
if fd < 0 {
return 0
}
ptr := noescape(unsafe.Pointer(&numbuf[0]))
n := read(fd, ptr, int32(len(numbuf)))
closefd(fd)
if n <= 0 {
return 0
}
n-- // remove trailing newline
v, ok := atoi(slicebytetostringtmp((*byte)(ptr), int(n)))
if !ok || v < 0 {
v = 0
}
if v&(v-1) != 0 {
// v is not a power of 2
return 0
}
return uintptr(v)
}
func osinit() {
ncpu = getproccount()
physHugePageSize = getHugePageSize()
osArchInit()
}
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
}
func gettid() uint32
// Called to initialize a new m (including the bootstrap m).
// Called on the new thread, cannot allocate memory.
func minit() {
minitSignals()
// Cgo-created threads and the bootstrap m are missing a
// procid. We need this for asynchronous preemption and it's
// useful in debuggers.
getg().m.procid = uint64(gettid())
}
// Called from dropm to undo the effect of an minit.
//go:nosplit
func unminit() {
unminitSignals()
}
//#ifdef GOARCH_386
//#define sa_handler k_sa_handler
//#endif
func sigreturn()
func sigtramp(sig uint32, info *siginfo, ctx unsafe.Pointer)
func cgoSigtramp()
//go:noescape
func sigaltstack(new, old *stackt)
//go:noescape
func setitimer(mode int32, new, old *itimerval)
//go:noescape
func rtsigprocmask(how int32, new, old *sigset, size int32)
//go:nosplit
//go:nowritebarrierrec
func sigprocmask(how int32, new, old *sigset) {
rtsigprocmask(how, new, old, int32(unsafe.Sizeof(*new)))
}
func raise(sig uint32)
func raiseproc(sig uint32)
//go:noescape
func sched_getaffinity(pid, len uintptr, buf *byte) int32
func osyield()
func pipe() (r, w int32, errno int32)
func pipe2(flags int32) (r, w int32, errno int32)
func setNonblock(fd int32)
//go:nosplit
//go:nowritebarrierrec
func setsig(i uint32, fn uintptr) {
var sa sigactiont
sa.sa_flags = _SA_SIGINFO | _SA_ONSTACK | _SA_RESTORER | _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
sigaction(i, &sa, nil)
}
//go:nosplit
//go:nowritebarrierrec
func setsigstack(i uint32) {
var sa sigactiont
sigaction(i, nil, &sa)
if sa.sa_flags&_SA_ONSTACK != 0 {
return
}
sa.sa_flags |= _SA_ONSTACK
sigaction(i, &sa, nil)
}
//go:nosplit
//go:nowritebarrierrec
func getsig(i uint32) uintptr {
var sa sigactiont
sigaction(i, nil, &sa)
return sa.sa_handler
}
// setSignaltstackSP sets the ss_sp field of a stackt.
//go:nosplit
func setSignalstackSP(s *stackt, sp uintptr) {
*(*uintptr)(unsafe.Pointer(&s.ss_sp)) = sp
}
//go:nosplit
func (c *sigctxt) fixsigcode(sig uint32) {
}
// sysSigaction calls the rt_sigaction system call.
//go:nosplit
func sysSigaction(sig uint32, new, old *sigactiont) {
if rt_sigaction(uintptr(sig), new, old, unsafe.Sizeof(sigactiont{}.sa_mask)) != 0 {
// Workaround for bugs in QEMU user mode emulation.
//
// QEMU turns calls to the sigaction system call into
// calls to the C library sigaction call; the C
// library call rejects attempts to call sigaction for
// SIGCANCEL (32) or SIGSETXID (33).
//
// QEMU rejects calling sigaction on SIGRTMAX (64).
//
// Just ignore the error in these case. There isn't
// anything we can do about it anyhow.
if sig != 32 && sig != 33 && sig != 64 {
// Use system stack to avoid split stack overflow on ppc64/ppc64le.
systemstack(func() {
throw("sigaction failed")
})
}
}
}
// rt_sigaction is implemented in assembly.
//go:noescape
func rt_sigaction(sig uintptr, new, old *sigactiont, size uintptr) int32
func getpid() int
func tgkill(tgid, tid, sig int)
// signalM sends a signal to mp.
func signalM(mp *m, sig int) {
tgkill(getpid(), int(mp.procid), sig)
}