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Text file src/runtime/cgo/gcc_android_amd64.c

Documentation: runtime/cgo

     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;

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