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// 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 <pthread.h>
#include "libcgo.h"
static void* threadentry(void*);
static pthread_key_t k1, k2;
static void
inittls(void)
{
uint32 x, y;
pthread_key_t tofree[16], k;
int i, ntofree;
int havek1, havek2;
/*
* Allocate thread-local storage slots for m, g.
* The key numbers start at 0x100, and we expect to be
* one of the early calls to pthread_key_create, so we
* should be able to get pretty low numbers.
*
* In Darwin/386 pthreads, %gs points at the thread
* structure, and each key is an index into the thread-local
* storage array that begins at offset 0x48 within in that structure.
* It may happen that we are not quite the first function to try
* to allocate thread-local storage keys, so instead of depending
* on getting 0x100 and 0x101, we try for 0x108 and 0x109,
* allocating keys until we get the ones we want and then freeing
* the ones we didn't want.
*
* Thus the final offsets to use in %gs references are
* 0x48+4*0x108 = 0x468 and 0x48+4*0x109 = 0x46c.
*
* The linker and runtime hard-code these constant offsets
* from %gs where we expect to find m and g. The code
* below verifies that the constants are correct once it has
* obtained the keys. Known to ../cmd/8l/obj.c:/468
* and to ../pkg/runtime/darwin/386/sys.s:/468
*
* This is truly disgusting and a bit fragile, but taking care
* of it here protects the rest of the system from damage.
* The alternative would be to use a global variable that
* held the offset and refer to that variable each time we
* need a %gs variable (m or g). That approach would
* require an extra instruction and memory reference in
* every stack growth prolog and would also require
* rewriting the code that 8c generates for extern registers.
*/
havek1 = 0;
havek2 = 0;
ntofree = 0;
while(!havek1 || !havek2) {
if(pthread_key_create(&k, nil) < 0) {
fprintf(stderr, "libcgo: pthread_key_create failed\n");
abort();
}
if(k == 0x108) {
havek1 = 1;
k1 = k;
continue;
}
if(k == 0x109) {
havek2 = 1;
k2 = k;
continue;
}
if(ntofree >= nelem(tofree)) {
fprintf(stderr, "libcgo: could not obtain pthread_keys\n");
fprintf(stderr, "\twanted 0x108 and 0x109\n");
fprintf(stderr, "\tgot");
for(i=0; i<ntofree; i++)
fprintf(stderr, " %#lx", tofree[i]);
fprintf(stderr, "\n");
abort();
}
tofree[ntofree++] = k;
}
for(i=0; i<ntofree; i++)
pthread_key_delete(tofree[i]);
/*
* We got the keys we wanted. Make sure that we observe
* updates to k1 at 0x468, to verify that the TLS array
* offset from %gs hasn't changed.
*/
pthread_setspecific(k1, (void*)0x12345678);
asm volatile("movl %%gs:0x468, %0" : "=r"(x));
pthread_setspecific(k1, (void*)0x87654321);
asm volatile("movl %%gs:0x468, %0" : "=r"(y));
if(x != 0x12345678 || y != 0x87654321) {
printf("libcgo: thread-local storage %#lx not at %%gs:0x468 - x=%#x y=%#x\n", k1, x, y);
abort();
}
}
static void
xinitcgo(void)
{
inittls();
}
void (*initcgo)(void) = xinitcgo;
void
libcgo_sys_thread_start(ThreadStart *ts)
{
pthread_attr_t attr;
pthread_t p;
size_t size;
pthread_attr_init(&attr);
pthread_attr_getstacksize(&attr, &size);
ts->g->stackguard = size;
pthread_create(&p, &attr, threadentry, ts);
}
static void*
threadentry(void *v)
{
ThreadStart ts;
ts = *(ThreadStart*)v;
free(v);
ts.g->stackbase = (uintptr)&ts;
/*
* libcgo_sys_thread_start set stackguard to stack size;
* change to actual guard pointer.
*/
ts.g->stackguard = (uintptr)&ts - ts.g->stackguard + 4096;
pthread_setspecific(k1, (void*)ts.g);
pthread_setspecific(k2, (void*)ts.m);
crosscall_386(ts.fn);
return nil;
}
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