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