gcc_libinit_windows.c

     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  #define WIN32_LEAN_AND_MEAN
     6  #include <windows.h>
     7  #include <process.h>
     8  
     9  #include <stdio.h>
    10  #include <stdlib.h>
    11  #include <errno.h>
    12  
    13  #include "libcgo.h"
    14  #include "libcgo_windows.h"
    15  
    16  // Ensure there's one symbol marked __declspec(dllexport).
    17  // If there are no exported symbols, the unfortunate behavior of
    18  // the binutils linker is to also strip the relocations table,
    19  // resulting in non-PIE binary. The other option is the
    20  // --export-all-symbols flag, but we don't need to export all symbols
    21  // and this may overflow the export table (#40795).
    22  // See https://sourceware.org/bugzilla/show_bug.cgi?id=19011
    23  __declspec(dllexport) int _cgo_dummy_export;
    24  
    25  static volatile LONG runtime_init_once_gate = 0;
    26  static volatile LONG runtime_init_once_done = 0;
    27  
    28  static CRITICAL_SECTION runtime_init_cs;
    29  
    30  static HANDLE runtime_init_wait;
    31  static int runtime_init_done;
    32  
    33  uintptr_t x_cgo_pthread_key_created;
    34  void (*x_crosscall2_ptr)(void (*fn)(void *), void *, int, size_t);
    35  
    36  // Pre-initialize the runtime synchronization objects
    37  void
    38  _cgo_preinit_init() {
    39  	 runtime_init_wait = CreateEvent(NULL, TRUE, FALSE, NULL);
    40  	 if (runtime_init_wait == NULL) {
    41  		fprintf(stderr, "runtime: failed to create runtime initialization wait event.\n");
    42  		abort();
    43  	 }
    44  
    45  	 InitializeCriticalSection(&runtime_init_cs);
    46  }
    47  
    48  // Make sure that the preinit sequence has run.
    49  void
    50  _cgo_maybe_run_preinit() {
    51  	 if (!InterlockedExchangeAdd(&runtime_init_once_done, 0)) {
    52  			if (InterlockedIncrement(&runtime_init_once_gate) == 1) {
    53  				 _cgo_preinit_init();
    54  				 InterlockedIncrement(&runtime_init_once_done);
    55  			} else {
    56  				 // Decrement to avoid overflow.
    57  				 InterlockedDecrement(&runtime_init_once_gate);
    58  				 while(!InterlockedExchangeAdd(&runtime_init_once_done, 0)) {
    59  						Sleep(0);
    60  				 }
    61  			}
    62  	 }
    63  }
    64  
    65  void
    66  x_cgo_sys_thread_create(void (*func)(void*), void* arg) {
    67  	_cgo_beginthread(func, arg);
    68  }
    69  
    70  int
    71  _cgo_is_runtime_initialized() {
    72  	 EnterCriticalSection(&runtime_init_cs);
    73  	 int status = runtime_init_done;
    74  	 LeaveCriticalSection(&runtime_init_cs);
    75  	 return status;
    76  }
    77  
    78  uintptr_t
    79  _cgo_wait_runtime_init_done(void) {
    80  	void (*pfn)(struct context_arg*);
    81  
    82  	 _cgo_maybe_run_preinit();
    83  	while (!_cgo_is_runtime_initialized()) {
    84  			WaitForSingleObject(runtime_init_wait, INFINITE);
    85  	}
    86  	pfn = _cgo_get_context_function();
    87  	if (pfn != nil) {
    88  		struct context_arg arg;
    89  
    90  		arg.Context = 0;
    91  		(*pfn)(&arg);
    92  		return arg.Context;
    93  	}
    94  	return 0;
    95  }
    96  
    97  // Should not be used since x_cgo_pthread_key_created will always be zero.
    98  void x_cgo_bindm(void* dummy) {
    99  	fprintf(stderr, "unexpected cgo_bindm on Windows\n");
   100  	abort();
   101  }
   102  
   103  void
   104  x_cgo_notify_runtime_init_done(void* dummy) {
   105  	 _cgo_maybe_run_preinit();
   106  
   107  	 EnterCriticalSection(&runtime_init_cs);
   108  	runtime_init_done = 1;
   109  	 LeaveCriticalSection(&runtime_init_cs);
   110  
   111  	 if (!SetEvent(runtime_init_wait)) {
   112  		fprintf(stderr, "runtime: failed to signal runtime initialization complete.\n");
   113  		abort();
   114  	}
   115  }
   116  
   117  // The context function, used when tracing back C calls into Go.
   118  static void (*cgo_context_function)(struct context_arg*);
   119  
   120  // Sets the context function to call to record the traceback context
   121  // when calling a Go function from C code. Called from runtime.SetCgoTraceback.
   122  void x_cgo_set_context_function(void (*context)(struct context_arg*)) {
   123  	EnterCriticalSection(&runtime_init_cs);
   124  	cgo_context_function = context;
   125  	LeaveCriticalSection(&runtime_init_cs);
   126  }
   127  
   128  // Gets the context function.
   129  void (*(_cgo_get_context_function(void)))(struct context_arg*) {
   130  	void (*ret)(struct context_arg*);
   131  
   132  	EnterCriticalSection(&runtime_init_cs);
   133  	ret = cgo_context_function;
   134  	LeaveCriticalSection(&runtime_init_cs);
   135  	return ret;
   136  }
   137  
   138  void _cgo_beginthread(void (*func)(void*), void* arg) {
   139  	int tries;
   140  	uintptr_t thandle;
   141  
   142  	for (tries = 0; tries < 20; tries++) {
   143  		thandle = _beginthread(func, 0, arg);
   144  		if (thandle == -1 && errno == EACCES) {
   145  			// "Insufficient resources", try again in a bit.
   146  			//
   147  			// Note that the first Sleep(0) is a yield.
   148  			Sleep(tries); // milliseconds
   149  			continue;
   150  		} else if (thandle == -1) {
   151  			break;
   152  		}
   153  		return; // Success!
   154  	}
   155  
   156  	fprintf(stderr, "runtime: failed to create new OS thread (%d)\n", errno);
   157  	abort();
   158  }
   159
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