/*
* OS X system constants - offset from 0(GS) to our TLS.
- * Explained in src/runtime/cgo/gcc_darwin_*.c.
*/
case objabi.Hdarwin:
switch ctxt.Arch.Family {
default:
log.Fatalf("unknown thread-local storage offset for darwin/%s", ctxt.Arch.Name)
- case sys.ARM:
- ctxt.Tlsoffset = 0 // dummy value, not needed
+ /*
+ * For x86, Apple has reserved a slot in the TLS for Go. See issue 23617.
+ * That slot is at offset 0x30 on amd64, and 0x18 on 386.
+ * The slot will hold the G pointer.
+ * These constants should match those in runtime/sys_darwin_{386,amd64}.s
+ * and runtime/cgo/gcc_darwin_{386,amd64}.c.
+ */
+ case sys.I386:
+ ctxt.Tlsoffset = 0x18
case sys.AMD64:
- ctxt.Tlsoffset = 0x8a0
+ ctxt.Tlsoffset = 0x30
- case sys.ARM64:
+ case sys.ARM:
ctxt.Tlsoffset = 0 // dummy value, not needed
- case sys.I386:
- ctxt.Tlsoffset = 0x468
+ case sys.ARM64:
+ ctxt.Tlsoffset = 0 // dummy value, not needed
}
}
#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 src/cmd/link/internal/ld/sym.go:/0x468
- * and to src/runtime/sys_darwin_386.s:/0x468
- *
- * 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_getstacksize(&attr, &size);
g->stacklo = (uintptr)&attr - size + 4096;
pthread_attr_destroy(&attr);
-
- inittls();
}
ts = *(ThreadStart*)v;
free(v);
- if (pthread_setspecific(k1, (void*)ts.g) != 0) {
- fprintf(stderr, "runtime/cgo: pthread_setspecific failed\n");
- abort();
- }
+ // Move the g pointer into the slot reserved in thread local storage.
+ // Constant must match the one in cmd/link/internal/ld/sym.go.
+ asm volatile("movq %0, %%gs:0x18" :: "r"(ts.g));
crosscall_386(ts.fn);
return nil;
#include "libcgo_unix.h"
static void* threadentry(void*);
-static pthread_key_t k1;
-
-#define magic1 (0x23581321345589ULL)
-
-static void
-inittls(void)
-{
- uint64 x;
- pthread_key_t tofree[128], k;
- int i, ntofree;
-
- /*
- * Same logic, code as darwin_386.c:/inittls, except that words
- * are 8 bytes long now, and the thread-local storage starts
- * at 0x60 on Leopard / Snow Leopard. So the offset is
- * 0x60+8*0x108 = 0x8a0.
- *
- * The linker and runtime hard-code this constant offset
- * from %gs where we expect to find g.
- * Known to src/cmd/link/internal/ld/sym.go:/0x8a0
- * and to src/runtime/sys_darwin_amd64.s:/0x8a0
- *
- * As disgusting as on the 386; same justification.
- */
- 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("movq %%gs:0x8a0, %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_getstacksize(&attr, &size);
g->stacklo = (uintptr)&attr - size + 4096;
pthread_attr_destroy(&attr);
-
- inittls();
}
ts = *(ThreadStart*)v;
free(v);
- if (pthread_setspecific(k1, (void*)ts.g) != 0) {
- fprintf(stderr, "runtime/cgo: pthread_setspecific failed\n");
- abort();
- }
+ // Move the g pointer into the slot reserved in thread local storage.
+ // Constant must match the one in cmd/link/internal/ld/sym.go.
+ asm volatile("movq %0, %%gs:0x30" :: "r"(ts.g));
crosscall_amd64(ts.fn);
return nil;
* When linking against the system libraries,
* we use its pthread_create and let it set up %gs
* for us. When we do that, the private storage
- * we get is not at 0(GS) but at 0x468(GS).
- * 8l rewrites 0(TLS) into 0x468(GS) for us.
+ * we get is not at 0(GS) but at 0x18(GS).
+ * The linker rewrites 0(TLS) into 0x18(GS) for us.
* To accommodate that rewrite, we translate the
- * address and limit here so that 0x468(GS) maps to 0(address).
+ * address here so that 0x18(GS) maps to 0(address).
*
- * See cgo/gcc_darwin_386.c:/468 for the derivation
- * of the constant.
+ * Constant must match the one in cmd/link/internal/ld/sym.go.
*/
- SUBL $0x468, BX
+ SUBL $0x18, BX
/*
* Must set up as USER_CTHREAD segment because
// set tls base to DI
TEXT runtime·settls(SB),NOSPLIT,$32
/*
- * Same as in sys_darwin_386.s:/ugliness, different constant.
- * See cgo/gcc_darwin_amd64.c for the derivation
- * of the constant.
- */
- SUBQ $0x8a0, DI
+ * Same as in sys_darwin_386.s, but a different constant.
+ * Constant must match the one in cmd/link/internal/ld/sym.go.
+ */
+ SUBQ $0x30, DI
MOVL $(0x3000000+3), AX // thread_fast_set_cthread_self - machdep call #3
SYSCALL