root/src/pkg/runtime/cgo/gcc_openbsd_amd64.c

DEFINITIONS

1. tcb_fixup
2. thread_start_wrapper
3. pthread_create
4. x_cgo_init
5. _cgo_sys_thread_start
6. threadentry

// 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 <sys/types.h>
#include <dlfcn.h>
#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <string.h>
#include "libcgo.h"

static void* threadentry(void*);
static void (*setmg_gcc)(void*, void*);

// TCB_SIZE is sizeof(struct thread_control_block),
// as defined in /usr/src/lib/librthread/tcb.h
#define TCB_SIZE (4 * sizeof(void *))
#define TLS_SIZE (2 * sizeof(void *))

void *__get_tcb(void);
void __set_tcb(void *);

static int (*sys_pthread_create)(pthread_t *thread, const pthread_attr_t *attr,
        void *(*start_routine)(void *), void *arg);

struct thread_args {
        void *(*func)(void *);
        void *arg;
};

static void
tcb_fixup(int mainthread)
{
        void *newtcb, *oldtcb;

        // The OpenBSD ld.so(1) does not currently support PT_TLS. As a result,
        // we need to allocate our own TLS space while preserving the existing
        // TCB that has been setup via librthread.

        newtcb = malloc(TCB_SIZE + TLS_SIZE);
        if(newtcb == NULL)
                abort();

        // The signal trampoline expects the TLS slots to be zeroed.
        bzero(newtcb, TLS_SIZE);

        oldtcb = __get_tcb();
        bcopy(oldtcb, newtcb + TLS_SIZE, TCB_SIZE);
        __set_tcb(newtcb + TLS_SIZE);

        // NOTE(jsing, minux): we can't free oldtcb without causing double-free
        // problem. so newtcb will be memory leaks. Get rid of this when OpenBSD
        // has proper support for PT_TLS.
}

static void *
thread_start_wrapper(void *arg)
{
        struct thread_args args = *(struct thread_args *)arg;

        free(arg);
        tcb_fixup(0);

        return args.func(args.arg);
}

int
pthread_create(pthread_t *thread, const pthread_attr_t *attr,
        void *(*start_routine)(void *), void *arg)
{
        struct thread_args *p;

        p = malloc(sizeof(*p));
        if(p == NULL) {
                errno = ENOMEM;
                return -1;
        }
        p->func = start_routine;
        p->arg = arg;

        return sys_pthread_create(thread, attr, thread_start_wrapper, p);
}

void
x_cgo_init(G *g, void (*setmg)(void*, void*))
{
        pthread_attr_t attr;
        size_t size;
        void *handle;

        setmg_gcc = setmg;
        pthread_attr_init(&attr);
        pthread_attr_getstacksize(&attr, &size);
        g->stackguard = (uintptr)&attr - size + 4096;
        pthread_attr_destroy(&attr);

        // Locate symbol for the system pthread_create function.
        handle = dlopen("libpthread.so", RTLD_LAZY);
        if(handle == NULL) {
                fprintf(stderr, "dlopen: failed to load libpthread: %s\n", dlerror());
                abort();
        }
        sys_pthread_create = dlsym(handle, "pthread_create");
        if(sys_pthread_create == NULL) {
                fprintf(stderr, "dlsym: failed to find pthread_create: %s\n", dlerror());
                abort();
        }
        dlclose(handle);

        tcb_fixup(1);
}


void
_cgo_sys_thread_start(ThreadStart *ts)
{
        pthread_attr_t attr;
        sigset_t ign, oset;
        pthread_t p;
        size_t size;
        int err;

        sigfillset(&ign);
        pthread_sigmask(SIG_SETMASK, &ign, &oset);

        pthread_attr_init(&attr);
        pthread_attr_getstacksize(&attr, &size);

        ts->g->stackguard = size;
        err = sys_pthread_create(&p, &attr, threadentry, ts);

        pthread_sigmask(SIG_SETMASK, &oset, nil);

        if (err != 0) {
                fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));
                abort();
        }
}

static void*
threadentry(void *v)
{
        ThreadStart ts;

        tcb_fixup(0);

        ts = *(ThreadStart*)v;
        free(v);

        ts.g->stackbase = (uintptr)&ts;

        /*
         * _cgo_sys_thread_start set stackguard to stack size;
         * change to actual guard pointer.
         */
        ts.g->stackguard = (uintptr)&ts - ts.g->stackguard + 4096;

        /*
         * Set specific keys.
         */
        setmg_gcc((void*)ts.m, (void*)ts.g);

        crosscall_amd64(ts.fn);
        return nil;
}