github.com/euank/go@v0.0.0-20160829210321-495514729181/src/runtime/cgo/gcc_darwin_arm.c (about)

     1  // Copyright 2014 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 <limits.h>
     6  #include <pthread.h>
     7  #include <signal.h>
     8  #include <string.h> /* for strerror */
     9  #include <sys/param.h>
    10  #include <unistd.h>
    11  
    12  #include "libcgo.h"
    13  
    14  #include <CoreFoundation/CFBundle.h>
    15  #include <CoreFoundation/CFString.h>
    16  
    17  #define magic (0xe696c4f4U)
    18  
    19  // inittls allocates a thread-local storage slot for g.
    20  //
    21  // It finds the first available slot using pthread_key_create and uses
    22  // it as the offset value for runtime.tlsg.
    23  static void
    24  inittls(void **tlsg, void **tlsbase)
    25  {
    26  	pthread_key_t k;
    27  	int i, err;
    28  
    29  	err = pthread_key_create(&k, nil);
    30  	if(err != 0) {
    31  		fprintf(stderr, "runtime/cgo: pthread_key_create failed: %d\n", err);
    32  		abort();
    33  	}
    34  	//fprintf(stderr, "runtime/cgo: k = %d, tlsbase = %p\n", (int)k, tlsbase); // debug
    35  	pthread_setspecific(k, (void*)magic);
    36  	// The first key should be at 258.
    37  	for (i=0; i<PTHREAD_KEYS_MAX; i++) {
    38  		if (*(tlsbase+i) == (void*)magic) {
    39  			*tlsg = (void*)(i*sizeof(void *));
    40  			pthread_setspecific(k, 0);
    41  			return;
    42  		}
    43  	}
    44  	fprintf(stderr, "runtime/cgo: could not find pthread key.\n");
    45  	abort();
    46  }
    47  
    48  static void *threadentry(void*);
    49  void (*setg_gcc)(void*);
    50  
    51  void
    52  _cgo_sys_thread_start(ThreadStart *ts)
    53  {
    54  	pthread_attr_t attr;
    55  	sigset_t ign, oset;
    56  	pthread_t p;
    57  	size_t size;
    58  	int err;
    59  
    60  	sigfillset(&ign);
    61  	pthread_sigmask(SIG_SETMASK, &ign, &oset);
    62  
    63  	pthread_attr_init(&attr);
    64  	size = 0;
    65  	pthread_attr_getstacksize(&attr, &size);
    66  	// Leave stacklo=0 and set stackhi=size; mstack will do the rest.
    67  	ts->g->stackhi = size;
    68  	err = pthread_create(&p, &attr, threadentry, ts);
    69  
    70  	pthread_sigmask(SIG_SETMASK, &oset, nil);
    71  
    72  	if (err != 0) {
    73  		fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));
    74  		abort();
    75  	}
    76  }
    77  
    78  extern void crosscall_arm1(void (*fn)(void), void (*setg_gcc)(void*), void *g);
    79  static void*
    80  threadentry(void *v)
    81  {
    82  	ThreadStart ts;
    83  
    84  	ts = *(ThreadStart*)v;
    85  	free(v);
    86  
    87  	darwin_arm_init_thread_exception_port();
    88  
    89  	crosscall_arm1(ts.fn, setg_gcc, (void*)ts.g);
    90  	return nil;
    91  }
    92  
    93  // init_working_dir sets the current working directory to the app root.
    94  // By default darwin/arm processes start in "/".
    95  static void
    96  init_working_dir()
    97  {
    98  	CFBundleRef bundle = CFBundleGetMainBundle();
    99  	if (bundle == NULL) {
   100  		fprintf(stderr, "runtime/cgo: no main bundle\n");
   101  		return;
   102  	}
   103  	CFURLRef url_ref = CFBundleCopyResourceURL(bundle, CFSTR("Info"), CFSTR("plist"), NULL);
   104  	if (url_ref == NULL) {
   105  		fprintf(stderr, "runtime/cgo: no Info.plist URL\n");
   106  		return;
   107  	}
   108  	CFStringRef url_str_ref = CFURLGetString(url_ref);
   109  	char url[MAXPATHLEN];
   110          if (!CFStringGetCString(url_str_ref, url, sizeof(url), kCFStringEncodingUTF8)) {
   111  		fprintf(stderr, "runtime/cgo: cannot get URL string\n");
   112  		return;
   113  	}
   114  
   115  	// url is of the form "file:///path/to/Info.plist".
   116  	// strip it down to the working directory "/path/to".
   117  	int url_len = strlen(url);
   118  	if (url_len < sizeof("file://")+sizeof("/Info.plist")) {
   119  		fprintf(stderr, "runtime/cgo: bad URL: %s\n", url);
   120  		return;
   121  	}
   122  	url[url_len-sizeof("/Info.plist")+1] = 0;
   123  	char *dir = &url[0] + sizeof("file://")-1;
   124  
   125  	if (chdir(dir) != 0) {
   126  		fprintf(stderr, "runtime/cgo: chdir(%s) failed\n", dir);
   127  	}
   128  
   129  	// No-op to set a breakpoint on, immediately after the real chdir.
   130  	// Gives the test harness in go_darwin_arm_exec (which uses lldb) a
   131  	// chance to move the working directory.
   132  	getwd(dir);
   133  }
   134  
   135  void
   136  x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
   137  {
   138  	pthread_attr_t attr;
   139  	size_t size;
   140  
   141  	setg_gcc = setg;
   142  	pthread_attr_init(&attr);
   143  	pthread_attr_getstacksize(&attr, &size);
   144  	g->stacklo = (uintptr)&attr - size + 4096;
   145  	pthread_attr_destroy(&attr);
   146  
   147  	// yes, tlsbase from mrc might not be correctly aligned.
   148  	inittls(tlsg, (void**)((uintptr)tlsbase & ~3));
   149  
   150  	darwin_arm_init_mach_exception_handler();
   151  	darwin_arm_init_thread_exception_port();
   152  	init_working_dir();
   153  }