root/src/pkg/runtime/os_linux.c

DEFINITIONS

1. runtime·futexsleep
2. runtime·futexwakeup
3. getproccount
4. runtime·newosproc
5. runtime·osinit
6. runtime·get_random_data
7. runtime·goenvs
8. runtime·mpreinit
9. runtime·minit
10. runtime·unminit
11. runtime·sigpanic
12. runtime·memlimit
13. runtime·setsig
14. runtime·getsig
15. runtime·signalstack
16. runtime·unblocksignals

// 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.

#include "runtime.h"
#include "defs_GOOS_GOARCH.h"
#include "os_GOOS.h"
#include "signal_unix.h"
#include "stack.h"
#include "../../cmd/ld/textflag.h"

extern SigTab runtime·sigtab[];

static Sigset sigset_none;
static Sigset sigset_all = { ~(uint32)0, ~(uint32)0 };

// 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.

enum
{
        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.
#pragma textflag NOSPLIT
void
runtime·futexsleep(uint32 *addr, uint32 val, int64 ns)
{
        Timespec ts;

        // 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) {
                runtime·futex(addr, FUTEX_WAIT, val, nil, nil, 0);
                return;
        }
        // NOTE: tv_nsec is int64 on amd64, so this assumes a little-endian system.
        ts.tv_nsec = 0;
        ts.tv_sec = runtime·timediv(ns, 1000000000LL, (int32*)&ts.tv_nsec);
        runtime·futex(addr, FUTEX_WAIT, val, &ts, nil, 0);
}

// If any procs are sleeping on addr, wake up at most cnt.
void
runtime·futexwakeup(uint32 *addr, uint32 cnt)
{
        int64 ret;

        ret = runtime·futex(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.
        runtime·printf("futexwakeup addr=%p returned %D\n", addr, ret);
        *(int32*)0x1006 = 0x1006;
}

extern runtime·sched_getaffinity(uintptr pid, uintptr len, uintptr *buf);
static int32
getproccount(void)
{
        uintptr buf[16], t;
        int32 r, cnt, i;

        cnt = 0;
        r = runtime·sched_getaffinity(0, sizeof(buf), buf);
        if(r > 0)
        for(i = 0; i < r/sizeof(buf[0]); i++) {
                t = buf[i];
                t = t - ((t >> 1) & 0x5555555555555555ULL);
                t = (t & 0x3333333333333333ULL) + ((t >> 2) & 0x3333333333333333ULL);
                cnt += (int32)((((t + (t >> 4)) & 0xF0F0F0F0F0F0F0FULL) * 0x101010101010101ULL) >> 56);
        }

        return cnt ? cnt : 1;
}

// Clone, the Linux rfork.
enum
{
        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,
};

void
runtime·newosproc(M *mp, void *stk)
{
        int32 ret;
        int32 flags;
        Sigset oset;

        /*
         * note: strace gets confused if we use CLONE_PTRACE here.
         */
        flags = 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 */
                ;

        mp->tls[0] = mp->id;    // so 386 asm can find it
        if(0){
                runtime·printf("newosproc stk=%p m=%p g=%p clone=%p id=%d/%d ostk=%p\n",
                        stk, mp, mp->g0, runtime·clone, mp->id, (int32)mp->tls[0], &mp);
        }

        // Disable signals during clone, so that the new thread starts
        // with signals disabled.  It will enable them in minit.
        runtime·rtsigprocmask(SIG_SETMASK, &sigset_all, &oset, sizeof oset);
        ret = runtime·clone(flags, stk, mp, mp->g0, runtime·mstart);
        runtime·rtsigprocmask(SIG_SETMASK, &oset, nil, sizeof oset);

        if(ret < 0) {
                runtime·printf("runtime: failed to create new OS thread (have %d already; errno=%d)\n", runtime·mcount(), -ret);
                runtime·throw("runtime.newosproc");
        }
}

void
runtime·osinit(void)
{
        runtime·ncpu = getproccount();
}

// Random bytes initialized at startup.  These come
// from the ELF AT_RANDOM auxiliary vector (vdso_linux_amd64.c).
byte*   runtime·startup_random_data;
uint32  runtime·startup_random_data_len;

void
runtime·get_random_data(byte **rnd, int32 *rnd_len)
{
        if(runtime·startup_random_data != nil) {
                *rnd = runtime·startup_random_data;
                *rnd_len = runtime·startup_random_data_len;
        } else {
                #pragma dataflag NOPTR
                static byte urandom_data[HashRandomBytes];
                int32 fd;
                fd = runtime·open("/dev/urandom", 0 /* O_RDONLY */, 0);
                if(runtime·read(fd, urandom_data, HashRandomBytes) == HashRandomBytes) {
                        *rnd = urandom_data;
                        *rnd_len = HashRandomBytes;
                } else {
                        *rnd = nil;
                        *rnd_len = 0;
                }
                runtime·close(fd);
        }
}

void
runtime·goenvs(void)
{
        runtime·goenvs_unix();
}

// Called to initialize a new m (including the bootstrap m).
// Called on the parent thread (main thread in case of bootstrap), can allocate memory.
void
runtime·mpreinit(M *mp)
{
        mp->gsignal = runtime·malg(32*1024);   // OS X wants >=8K, Linux >=2K
}

// Called to initialize a new m (including the bootstrap m).
// Called on the new thread, can not allocate memory.
void
runtime·minit(void)
{
        // Initialize signal handling.
        runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
        runtime·rtsigprocmask(SIG_SETMASK, &sigset_none, nil, sizeof(Sigset));
}

// Called from dropm to undo the effect of an minit.
void
runtime·unminit(void)
{
        runtime·signalstack(nil, 0);
}

void
runtime·sigpanic(void)
{
        if(!runtime·canpanic(g))
                runtime·throw("unexpected signal during runtime execution");

        switch(g->sig) {
        case SIGBUS:
                if(g->sigcode0 == BUS_ADRERR && g->sigcode1 < 0x1000 || g->paniconfault) {
                        if(g->sigpc == 0)
                                runtime·panicstring("call of nil func value");
                        runtime·panicstring("invalid memory address or nil pointer dereference");
                }
                runtime·printf("unexpected fault address %p\n", g->sigcode1);
                runtime·throw("fault");
        case SIGSEGV:
                if((g->sigcode0 == 0 || g->sigcode0 == SEGV_MAPERR || g->sigcode0 == SEGV_ACCERR) && g->sigcode1 < 0x1000 || g->paniconfault) {
                        if(g->sigpc == 0)
                                runtime·panicstring("call of nil func value");
                        runtime·panicstring("invalid memory address or nil pointer dereference");
                }
                runtime·printf("unexpected fault address %p\n", g->sigcode1);
                runtime·throw("fault");
        case SIGFPE:
                switch(g->sigcode0) {
                case FPE_INTDIV:
                        runtime·panicstring("integer divide by zero");
                case FPE_INTOVF:
                        runtime·panicstring("integer overflow");
                }
                runtime·panicstring("floating point error");
        }
        runtime·panicstring(runtime·sigtab[g->sig].name);
}

uintptr
runtime·memlimit(void)
{
        Rlimit rl;
        extern byte text[], 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 = end - 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;
}

#ifdef GOARCH_386
#define sa_handler k_sa_handler
#endif

/*
 * This assembler routine takes the args from registers, puts them on the stack,
 * and calls sighandler().
 */
extern void runtime·sigtramp(void);
extern void runtime·sigreturn(void);   // calls runtime·sigreturn

void
runtime·setsig(int32 i, GoSighandler *fn, bool restart)
{
        Sigaction sa;

        runtime·memclr((byte*)&sa, sizeof sa);
        sa.sa_flags = SA_ONSTACK | SA_SIGINFO | SA_RESTORER;
        if(restart)
                sa.sa_flags |= SA_RESTART;
        sa.sa_mask = ~0ULL;
        // TODO(adonovan): Linux manpage says "sa_restorer element is
        // obsolete and should not be used".  Avoid it here, and test.
        sa.sa_restorer = (void*)runtime·sigreturn;
        if(fn == runtime·sighandler)
                fn = (void*)runtime·sigtramp;
        sa.sa_handler = fn;
        if(runtime·rt_sigaction(i, &sa, nil, sizeof(sa.sa_mask)) != 0)
                runtime·throw("rt_sigaction failure");
}

GoSighandler*
runtime·getsig(int32 i)
{
        Sigaction sa;

        runtime·memclr((byte*)&sa, sizeof sa);
        if(runtime·rt_sigaction(i, nil, &sa, sizeof(sa.sa_mask)) != 0)
                runtime·throw("rt_sigaction read failure");
        if((void*)sa.sa_handler == runtime·sigtramp)
                return runtime·sighandler;
        return (void*)sa.sa_handler;
}

void
runtime·signalstack(byte *p, int32 n)
{
        Sigaltstack st;

        st.ss_sp = p;
        st.ss_size = n;
        st.ss_flags = 0;
        if(p == nil)
                st.ss_flags = SS_DISABLE;
        runtime·sigaltstack(&st, nil);
}

void
runtime·unblocksignals(void)
{
        runtime·rtsigprocmask(SIG_SETMASK, &sigset_none, nil, sizeof sigset_none);
}