code review 7560048: runtime: pass setmg function to cgo_init

src/pkg/runtime/cgo/gcc_openbsd_amd64.c

 // Copyright 2009 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 #include <sys/types.h>
 #include <dlfcn.h>
 #include <errno.h>
 #include <pthread.h>
 #include <signal.h>
 #include <string.h>
 #include "libcgo.h"
 
 static void* threadentry(void*);
+static void (*setmg_gcc)(void*, void*);
 
 // TCB_SIZE is sizeof(struct thread_control_block),
 // as defined in /usr/src/lib/librthread/tcb.h
 #define TCB_SIZE (4 * sizeof(void *))
 #define TLS_SIZE (2 * sizeof(void *))
 
 void *__get_tcb(void);
 void __set_tcb(void *);
 
 static int (*sys_pthread_create)(pthread_t *thread, const pthread_attr_t *attr,
@@ skipping 51 matching lines @@
                 errno = ENOMEM;
                 return -1;
         }
         p->func = start_routine;
         p->arg = arg;
 
         return sys_pthread_create(thread, attr, thread_start_wrapper, p);
 }
 
 void
-x_cgo_init(G *g)
+x_cgo_init(G *g, void (*setmg)(void*, void*))
 {
         pthread_attr_t attr;
         size_t size;
         void *handle;
 
+        setmg_gcc = setmg;
         pthread_attr_init(&attr);
         pthread_attr_getstacksize(&attr, &size);
         g->stackguard = (uintptr)&attr - size + 4096;
         pthread_attr_destroy(&attr);
 
         // Locate symbol for the system pthread_create function.
         handle = dlopen("libpthread.so", RTLD_LAZY);
         if(handle == NULL) {
                 fprintf(stderr, "dlopen: failed to load libpthread: %s\n", dlerror());
                 abort();
@@ skipping 47 matching lines @@
 
         ts.g->stackbase = (uintptr)&ts;
 
         /*
          * _cgo_sys_thread_start set stackguard to stack size;
          * change to actual guard pointer.
          */
         ts.g->stackguard = (uintptr)&ts - ts.g->stackguard + 4096;
 
         /*
-         * Set specific keys.  On OpenBSD/ELF, the thread local storage
-         * is just before %fs:0.  Our dynamic 6.out's reserve 16 bytes
-         * for the two words g and m at %fs:-16 and %fs:-8.
+         * Set specific keys.
          */
-        asm volatile (
-                "movq %0, %%fs:-16\n"   // MOVL g, -16(FS)
-                "movq %1, %%fs:-8\n"    // MOVL m, -8(FS)
-                :: "r"(ts.g), "r"(ts.m)
-        );
+        setmg_gcc((void*)ts.m, (void*)ts.g);
+
         crosscall_amd64(ts.fn);
         return nil;
 }