| // 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 <string.h> /* for strerror */ |
| #include <pthread.h> |
| #include <signal.h> |
| #include "libcgo.h" |
| #include "libcgo_unix.h" |
| |
| static void* threadentry(void*); |
| static pthread_key_t k1; |
| |
| #define magic1 (0x23581321U) |
| |
| static void |
| inittls(void) |
| { |
| uint32 x; |
| pthread_key_t tofree[128], k; |
| int i, ntofree; |
| |
| /* |
| * Allocate thread-local storage slot for 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 a pretty low number. |
| * |
| * 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, we try for 0x108, allocating keys until |
| * we get the one we want and then freeing the ones we didn't want. |
| * |
| * Thus the final offset to use in %gs references is |
| * 0x48+4*0x108 = 0x468. |
| * |
| * The linker and runtime hard-code this constant offset |
| * from %gs where we expect to find g. |
| * Known to ../../../liblink/sym.c:/468 |
| * and to ../sys_darwin_386.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 (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. |
| * |
| * Things get more disgusting on OS X 10.7 Lion. |
| * The 0x48 base mentioned above is the offset of the tsd |
| * array within the per-thread structure on Leopard and Snow Leopard. |
| * On Lion, the base moved a little, so while the math above |
| * still applies, the base is different. Thus, we cannot |
| * look for specific key values if we want to build binaries |
| * that run on both systems. Instead, forget about the |
| * specific key values and just allocate and initialize per-thread |
| * storage until we find a key that writes to the memory location |
| * we want. Then keep that key. |
| */ |
| ntofree = 0; |
| for(;;) { |
| if(pthread_key_create(&k, nil) < 0) { |
| fprintf(stderr, "runtime/cgo: pthread_key_create failed\n"); |
| abort(); |
| } |
| pthread_setspecific(k, (void*)magic1); |
| asm volatile("movl %%gs:0x468, %0" : "=r"(x)); |
| pthread_setspecific(k, 0); |
| if(x == magic1) { |
| k1 = k; |
| break; |
| } |
| if(ntofree >= nelem(tofree)) { |
| fprintf(stderr, "runtime/cgo: could not obtain pthread_keys\n"); |
| fprintf(stderr, "\ttried"); |
| for(i=0; i<ntofree; i++) |
| fprintf(stderr, " %#x", (unsigned)tofree[i]); |
| fprintf(stderr, "\n"); |
| abort(); |
| } |
| tofree[ntofree++] = k; |
| } |
| |
| /* |
| * We got the key we wanted. Free the others. |
| */ |
| for(i=0; i<ntofree; i++) |
| pthread_key_delete(tofree[i]); |
| } |
| |
| void |
| x_cgo_init(G *g) |
| { |
| pthread_attr_t attr; |
| size_t size; |
| |
| pthread_attr_init(&attr); |
| pthread_attr_getstacksize(&attr, &size); |
| g->stacklo = (uintptr)&attr - size + 4096; |
| pthread_attr_destroy(&attr); |
| |
| inittls(); |
| } |
| |
| |
| void |
| _cgo_sys_thread_start(ThreadStart *ts) |
| { |
| pthread_attr_t attr; |
| sigset_t ign, oset; |
| pthread_t p; |
| size_t size; |
| int err; |
| |
| sigfillset(&ign); |
| pthread_sigmask(SIG_SETMASK, &ign, &oset); |
| |
| pthread_attr_init(&attr); |
| pthread_attr_getstacksize(&attr, &size); |
| // Leave stacklo=0 and set stackhi=size; mstart will do the rest. |
| ts->g->stackhi = size; |
| err = _cgo_try_pthread_create(&p, &attr, threadentry, ts); |
| |
| pthread_sigmask(SIG_SETMASK, &oset, nil); |
| |
| if (err != 0) { |
| fprintf(stderr, "runtime/cgo: pthread_create failed: %s\n", strerror(err)); |
| abort(); |
| } |
| } |
| |
| static void* |
| threadentry(void *v) |
| { |
| ThreadStart ts; |
| |
| ts = *(ThreadStart*)v; |
| free(v); |
| |
| pthread_setspecific(k1, (void*)ts.g); |
| |
| crosscall_386(ts.fn); |
| return nil; |
| } |