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Diffstat (limited to 'src/runtime/os_linux.go')
| -rw-r--r-- | src/runtime/os_linux.go | 504 |
1 files changed, 504 insertions, 0 deletions
diff --git a/src/runtime/os_linux.go b/src/runtime/os_linux.go new file mode 100644 index 0000000..058c7da --- /dev/null +++ b/src/runtime/os_linux.go @@ -0,0 +1,504 @@ +// 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() + if iscgo { + // #42494 glibc and musl reserve some signals for + // internal use and require they not be blocked by + // the rest of a normal C runtime. When the go runtime + // blocks...unblocks signals, temporarily, the blocked + // interval of time is generally very short. As such, + // these expectations of *libc code are mostly met by + // the combined go+cgo system of threads. However, + // when go causes a thread to exit, via a return from + // mstart(), the combined runtime can deadlock if + // these signals are blocked. Thus, don't block these + // signals when exiting threads. + // - glibc: SIGCANCEL (32), SIGSETXID (33) + // - musl: SIGTIMER (32), SIGCANCEL (33), SIGSYNCCALL (34) + sigdelset(&sigsetAllExiting, 32) + sigdelset(&sigsetAllExiting, 33) + sigdelset(&sigsetAllExiting, 34) + } + 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() +} + +// Called from exitm, but not from drop, to undo the effect of thread-owned +// resources in minit, semacreate, or elsewhere. Do not take locks after calling this. +func mdestroy(mp *m) { +} + +//#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) +} |