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      1 // Copyright 2009 The Go Authors.  All rights reserved.
      2 // Use of this source code is governed by a BSD-style
      3 // license that can be found in the LICENSE file.
      4 
      5 #include <string.h> /* for strerror */
      6 #include <pthread.h>
      7 #include <signal.h>
      8 #include "libcgo.h"
      9 
     10 static void* threadentry(void*);
     11 static pthread_key_t k1;
     12 
     13 #define magic1 (0x23581321345589ULL)
     14 
     15 static void
     16 inittls(void)
     17 {
     18 	uint64 x;
     19 	pthread_key_t tofree[128], k;
     20 	int i, ntofree;
     21 
     22 	/*
     23 	 * Same logic, code as darwin_386.c:/inittls, except that words
     24 	 * are 8 bytes long now, and the thread-local storage starts
     25 	 * at 0x60 on Leopard / Snow Leopard. So the offset is
     26 	 * 0x60+8*0x108 = 0x8a0.
     27 	 *
     28 	 * The linker and runtime hard-code this constant offset
     29 	 * from %gs where we expect to find g.
     30 	 * Known to ../../../liblink/sym.c:/8a0
     31 	 * and to ../sys_darwin_amd64.s:/8a0
     32 	 *
     33 	 * As disgusting as on the 386; same justification.
     34 	 */
     35 	ntofree = 0;
     36 	for(;;) {
     37 		if(pthread_key_create(&k, nil) < 0) {
     38 			fprintf(stderr, "runtime/cgo: pthread_key_create failed\n");
     39 			abort();
     40 		}
     41 		pthread_setspecific(k, (void*)magic1);
     42 		asm volatile("movq %%gs:0x8a0, %0" : "=r"(x));
     43 		pthread_setspecific(k, 0);
     44 		if(x == magic1) {
     45 			k1 = k;
     46 			break;
     47 		}
     48 		if(ntofree >= nelem(tofree)) {
     49 			fprintf(stderr, "runtime/cgo: could not obtain pthread_keys\n");
     50 			fprintf(stderr, "\ttried");
     51 			for(i=0; i<ntofree; i++)
     52 				fprintf(stderr, " %#x", (unsigned)tofree[i]);
     53 			fprintf(stderr, "\n");
     54 			abort();
     55 		}
     56 		tofree[ntofree++] = k;
     57 	}
     58 
     59 	/*
     60 	 * We got the key we wanted.  Free the others.
     61 	 */
     62 	for(i=0; i<ntofree; i++)
     63 		pthread_key_delete(tofree[i]);
     64 }
     65 
     66 void
     67 x_cgo_init(G *g)
     68 {
     69 	pthread_attr_t attr;
     70 	size_t size;
     71 
     72 	pthread_attr_init(&attr);
     73 	pthread_attr_getstacksize(&attr, &size);
     74 	g->stacklo = (uintptr)&attr - size + 4096;
     75 	pthread_attr_destroy(&attr);
     76 
     77 	inittls();
     78 }
     79 
     80 
     81 void
     82 _cgo_sys_thread_start(ThreadStart *ts)
     83 {
     84 	pthread_attr_t attr;
     85 	sigset_t ign, oset;
     86 	pthread_t p;
     87 	size_t size;
     88 	int err;
     89 
     90 	sigfillset(&ign);
     91 	pthread_sigmask(SIG_SETMASK, &ign, &oset);
     92 
     93 	pthread_attr_init(&attr);
     94 	pthread_attr_getstacksize(&attr, &size);
     95 	// Leave stacklo=0 and set stackhi=size; mstack will do the rest.
     96 	ts->g->stackhi = size;
     97 	err = pthread_create(&p, &attr, threadentry, ts);
     98 
     99 	pthread_sigmask(SIG_SETMASK, &oset, nil);
    100 
    101 	if (err != 0) {
    102 		fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));
    103 		abort();
    104 	}
    105 }
    106 
    107 static void*
    108 threadentry(void *v)
    109 {
    110 	ThreadStart ts;
    111 
    112 	ts = *(ThreadStart*)v;
    113 	free(v);
    114 
    115 	pthread_setspecific(k1, (void*)ts.g);
    116 
    117 	crosscall_amd64(ts.fn);
    118 	return nil;
    119 }
    120