github.com/aloncn/graphics-go@v0.0.1/src/runtime/cgo/gcc_android_amd64.c (about)

     1  // Copyright 2015 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  // +build cgo
     6  
     7  #include <string.h> /* for strerror */
     8  #include <pthread.h>
     9  #include <signal.h>
    10  #include "libcgo.h"
    11  
    12  static void* threadentry(void*);
    13  static pthread_key_t k1;
    14  
    15  #define magic1 (0x23581321345589ULL)
    16  
    17  static void
    18  inittls(void)
    19  {
    20  	uint64 x;
    21  	pthread_key_t tofree[128], k;
    22  	int i, ntofree;
    23  
    24  	/*
    25  	 * Same logic, code as gcc_darwin_386.c:/inittls.
    26  	 * Note that this is a temporary hack that should be fixed soon.
    27  	 * Android-L and M bionic's pthread implementation differ
    28  	 * significantly, and can change any time.
    29  	 * https://android-review.googlesource.com/#/c/134202
    30  	 *
    31  	 * We chose %fs:0x1d0 which seems to work in testing with Android
    32  	 * emulators (API22, API23) but it may break any time.
    33  	 *
    34  	 * TODO: fix this.
    35  	 *
    36  	 * The linker and runtime hard-code this constant offset
    37  	 * from %fs where we expect to find g. Disgusting.
    38  	 *
    39  	 * Known to src/cmd/link/internal/ld/sym.go:/0x1d0
    40  	 * and to src/runtime/sys_linux_amd64.s:/0x1d0 or /GOOS_android.
    41  	 *
    42  	 * As disgusting as on the darwin/386, darwin/amd64.
    43  	 */
    44  	ntofree = 0;
    45  	for(;;) {
    46  		if(pthread_key_create(&k, nil) < 0) {
    47  			fprintf(stderr, "runtime/cgo: pthread_key_create failed\n");
    48  			abort();
    49  		}
    50  		pthread_setspecific(k, (void*)magic1);
    51  		asm volatile("movq %%fs:0x1d0, %0" : "=r"(x));
    52  		pthread_setspecific(k, 0);
    53  		if(x == magic1) {
    54  			k1 = k;
    55  			break;
    56  		}
    57  		if(ntofree >= nelem(tofree)) {
    58  			fprintf(stderr, "runtime/cgo: could not obtain pthread_keys\n");
    59  			fprintf(stderr, "\ttried");
    60  			for(i=0; i<ntofree; i++)
    61  				fprintf(stderr, " %#x", (unsigned)tofree[i]);
    62  			fprintf(stderr, "\n");
    63  			abort();
    64  		}
    65  		tofree[ntofree++] = k;
    66  	}
    67  	// TODO: output to stderr is not useful for apps.
    68  	// Can we fall back to Android's log library?
    69  
    70  	/*
    71  	 * We got the key we wanted.  Free the others.
    72  	 */
    73  	for(i=0; i<ntofree; i++) {
    74  		pthread_key_delete(tofree[i]);
    75  	}
    76  }
    77  
    78  
    79  static void*
    80  threadentry(void *v)
    81  {
    82  	ThreadStart ts;
    83  
    84  	ts = *(ThreadStart*)v;
    85  	free(v);
    86  
    87  	pthread_setspecific(k1, (void*)ts.g);
    88  
    89  	crosscall_amd64(ts.fn);
    90  	return nil;
    91  }
    92  
    93  void (*x_cgo_inittls)(void) = inittls;
    94  void* (*x_cgo_threadentry)(void*) = threadentry;