github.com/xushiwei/go@v0.0.0-20130601165731-2b9d83f45bc9/src/pkg/runtime/cgo/gcc_freebsd_arm.c (about)

     1  // Copyright 2012 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 <sys/types.h>
     6  #include <machine/sysarch.h>
     7  #include <pthread.h>
     8  #include <string.h>
     9  #include "libcgo.h"
    10  
    11  static void *threadentry(void*);
    12  
    13  // We have to resort to TLS variable to save g(R10) and
    14  // m(R9). One reason is that external code might trigger
    15  // SIGSEGV, and our runtime.sigtramp don't even know we
    16  // are in external code, and will continue to use R10/R9,
    17  // this might as well result in another SIGSEGV.
    18  // Note: all three functions will clobber R0, and the last
    19  // two can be called from 5c ABI code.
    20  void __aeabi_read_tp(void) __attribute__((naked));
    21  void x_cgo_save_gm(void) __attribute__((naked));
    22  void x_cgo_load_gm(void) __attribute__((naked));
    23  
    24  void
    25  __aeabi_read_tp(void)
    26  {
    27  	__asm__ __volatile__ (
    28  #ifdef ARM_TP_ADDRESS
    29  		// ARM_TP_ADDRESS is (ARM_VECTORS_HIGH + 0x1000) or 0xffff1000
    30  		// GCC inline asm doesn't provide a way to provide a constant
    31  		// to "ldr r0, =??" pseudo instruction, so we hardcode the value
    32  		// and check it with cpp.
    33  #if ARM_TP_ADDRESS != 0xffff1000
    34  #error Wrong ARM_TP_ADDRESS!
    35  #endif
    36  		"ldr r0, =0xffff1000\n\t"
    37  		"ldr r0, [r0]\n\t"
    38  #else
    39  		"mrc p15, 0, r0, c13, c0, 3\n\t"
    40  #endif
    41  		"mov pc, lr\n\t"
    42  	);
    43  }
    44  
    45  // g (R10) at 8(TP), m (R9) at 12(TP)
    46  void
    47  x_cgo_load_gm(void)
    48  {
    49  	__asm__ __volatile__ (
    50  		"push {lr}\n\t"
    51  		"bl __aeabi_read_tp\n\t"
    52  		"ldr r10, [r0, #8]\n\t"
    53  		"ldr r9, [r0, #12]\n\t"
    54  		"pop {pc}\n\t"
    55  	);
    56  }
    57  
    58  void
    59  x_cgo_save_gm(void)
    60  {
    61  	__asm__ __volatile__ (
    62  		"push {lr}\n\t"
    63  		"bl __aeabi_read_tp\n\t"
    64  		"str r10, [r0, #8]\n\t"
    65  		"str r9, [r0, #12]\n\t"
    66  		"pop {pc}\n\t"
    67  	);
    68  }
    69  
    70  void
    71  x_cgo_init(G *g)
    72  {
    73  	pthread_attr_t attr;
    74  	size_t size;
    75  	x_cgo_save_gm(); // save g and m for the initial thread
    76  
    77  	pthread_attr_init(&attr);
    78  	pthread_attr_getstacksize(&attr, &size);
    79  	g->stackguard = (uintptr)&attr - size + 4096;
    80  	pthread_attr_destroy(&attr);
    81  }
    82  
    83  
    84  void
    85  _cgo_sys_thread_start(ThreadStart *ts)
    86  {
    87  	pthread_attr_t attr;
    88  	pthread_t p;
    89  	size_t size;
    90  	int err;
    91  
    92  	// Not sure why the memset is necessary here,
    93  	// but without it, we get a bogus stack size
    94  	// out of pthread_attr_getstacksize.  C'est la Linux.
    95  	memset(&attr, 0, sizeof attr);
    96  	pthread_attr_init(&attr);
    97  	size = 0;
    98  	pthread_attr_getstacksize(&attr, &size);
    99  	ts->g->stackguard = size;
   100  	err = pthread_create(&p, &attr, threadentry, ts);
   101  	if (err != 0) {
   102  		fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err));
   103  		abort();
   104  	}
   105  }
   106  
   107  extern void crosscall_arm2(void (*fn)(void), void *g, void *m);
   108  static void*
   109  threadentry(void *v)
   110  {
   111  	ThreadStart ts;
   112  
   113  	ts = *(ThreadStart*)v;
   114  	free(v);
   115  
   116  	ts.g->stackbase = (uintptr)&ts;
   117  
   118  	/*
   119  	 * _cgo_sys_thread_start set stackguard to stack size;
   120  	 * change to actual guard pointer.
   121  	 */
   122  	ts.g->stackguard = (uintptr)&ts - ts.g->stackguard + 4096 * 2;
   123  
   124  	crosscall_arm2(ts.fn, (void *)ts.g, (void *)ts.m);
   125  	return nil;
   126  }