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runtime: use fixed TLS offsets on darwin/amd64 and darwin/386
Fixes #23617 Note that this CL does not affect darwin/arm and darwin/arm64, still TBD what, if anything, needs to be done for those. Change-Id: Ie1ee02a9f4d4d1fb9cd5dc432d900f926cc157db Reviewed-on: https://go-review.googlesource.com/105975 Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Keith Randall
parent
d01322826e
commit
76e92d1c9e
@ -113,24 +113,30 @@ func (ctxt *Link) computeTLSOffset() {
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/*
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* OS X system constants - offset from 0(GS) to our TLS.
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* Explained in src/runtime/cgo/gcc_darwin_*.c.
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*/
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case objabi.Hdarwin:
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switch ctxt.Arch.Family {
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default:
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log.Fatalf("unknown thread-local storage offset for darwin/%s", ctxt.Arch.Name)
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/*
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* For x86, Apple has reserved a slot in the TLS for Go. See issue 23617.
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* That slot is at offset 0x30 on amd64, and 0x18 on 386.
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* The slot will hold the G pointer.
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* These constants should match those in runtime/sys_darwin_{386,amd64}.s
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* and runtime/cgo/gcc_darwin_{386,amd64}.c.
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*/
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case sys.I386:
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ctxt.Tlsoffset = 0x18
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case sys.AMD64:
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ctxt.Tlsoffset = 0x30
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case sys.ARM:
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ctxt.Tlsoffset = 0 // dummy value, not needed
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case sys.AMD64:
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ctxt.Tlsoffset = 0x8a0
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case sys.ARM64:
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ctxt.Tlsoffset = 0 // dummy value, not needed
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case sys.I386:
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ctxt.Tlsoffset = 0x468
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}
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}
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@ -9,89 +9,6 @@
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#include "libcgo_unix.h"
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static void* threadentry(void*);
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static pthread_key_t k1;
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#define magic1 (0x23581321U)
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static void
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inittls(void)
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{
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uint32 x;
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pthread_key_t tofree[128], k;
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int i, ntofree;
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/*
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* Allocate thread-local storage slot for g.
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* The key numbers start at 0x100, and we expect to be
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* one of the early calls to pthread_key_create, so we
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* should be able to get a pretty low number.
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*
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* In Darwin/386 pthreads, %gs points at the thread
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* structure, and each key is an index into the thread-local
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* storage array that begins at offset 0x48 within in that structure.
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* It may happen that we are not quite the first function to try
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* to allocate thread-local storage keys, so instead of depending
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* on getting 0x100, we try for 0x108, allocating keys until
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* we get the one we want and then freeing the ones we didn't want.
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*
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* Thus the final offset to use in %gs references is
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* 0x48+4*0x108 = 0x468.
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*
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* The linker and runtime hard-code this constant offset
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* from %gs where we expect to find g.
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* Known to src/cmd/link/internal/ld/sym.go:/0x468
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* and to src/runtime/sys_darwin_386.s:/0x468
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*
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* This is truly disgusting and a bit fragile, but taking care
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* of it here protects the rest of the system from damage.
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* The alternative would be to use a global variable that
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* held the offset and refer to that variable each time we
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* need a %gs variable (g). That approach would
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* require an extra instruction and memory reference in
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* every stack growth prolog and would also require
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* rewriting the code that 8c generates for extern registers.
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*
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* Things get more disgusting on OS X 10.7 Lion.
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* The 0x48 base mentioned above is the offset of the tsd
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* array within the per-thread structure on Leopard and Snow Leopard.
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* On Lion, the base moved a little, so while the math above
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* still applies, the base is different. Thus, we cannot
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* look for specific key values if we want to build binaries
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* that run on both systems. Instead, forget about the
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* specific key values and just allocate and initialize per-thread
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* storage until we find a key that writes to the memory location
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* we want. Then keep that key.
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*/
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ntofree = 0;
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for(;;) {
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if(pthread_key_create(&k, nil) != 0) {
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fprintf(stderr, "runtime/cgo: pthread_key_create failed\n");
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abort();
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}
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pthread_setspecific(k, (void*)magic1);
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asm volatile("movl %%gs:0x468, %0" : "=r"(x));
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pthread_setspecific(k, 0);
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if(x == magic1) {
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k1 = k;
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break;
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}
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if(ntofree >= nelem(tofree)) {
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fprintf(stderr, "runtime/cgo: could not obtain pthread_keys\n");
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fprintf(stderr, "\ttried");
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for(i=0; i<ntofree; i++)
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fprintf(stderr, " %#x", (unsigned)tofree[i]);
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fprintf(stderr, "\n");
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abort();
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}
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tofree[ntofree++] = k;
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}
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/*
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* We got the key we wanted. Free the others.
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*/
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for(i=0; i<ntofree; i++)
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pthread_key_delete(tofree[i]);
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}
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void
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x_cgo_init(G *g)
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@ -103,8 +20,6 @@ x_cgo_init(G *g)
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pthread_attr_getstacksize(&attr, &size);
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g->stacklo = (uintptr)&attr - size + 4096;
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pthread_attr_destroy(&attr);
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inittls();
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}
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@ -142,10 +57,9 @@ threadentry(void *v)
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ts = *(ThreadStart*)v;
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free(v);
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if (pthread_setspecific(k1, (void*)ts.g) != 0) {
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fprintf(stderr, "runtime/cgo: pthread_setspecific failed\n");
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abort();
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}
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// Move the g pointer into the slot reserved in thread local storage.
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// Constant must match the one in cmd/link/internal/ld/sym.go.
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asm volatile("movq %0, %%gs:0x18" :: "r"(ts.g));
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crosscall_386(ts.fn);
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return nil;
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@ -9,60 +9,6 @@
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#include "libcgo_unix.h"
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static void* threadentry(void*);
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static pthread_key_t k1;
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#define magic1 (0x23581321345589ULL)
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static void
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inittls(void)
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{
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uint64 x;
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pthread_key_t tofree[128], k;
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int i, ntofree;
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/*
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* Same logic, code as darwin_386.c:/inittls, except that words
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* are 8 bytes long now, and the thread-local storage starts
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* at 0x60 on Leopard / Snow Leopard. So the offset is
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* 0x60+8*0x108 = 0x8a0.
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*
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* The linker and runtime hard-code this constant offset
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* from %gs where we expect to find g.
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* Known to src/cmd/link/internal/ld/sym.go:/0x8a0
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* and to src/runtime/sys_darwin_amd64.s:/0x8a0
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*
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* As disgusting as on the 386; same justification.
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*/
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ntofree = 0;
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for(;;) {
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if(pthread_key_create(&k, nil) != 0) {
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fprintf(stderr, "runtime/cgo: pthread_key_create failed\n");
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abort();
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}
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pthread_setspecific(k, (void*)magic1);
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asm volatile("movq %%gs:0x8a0, %0" : "=r"(x));
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pthread_setspecific(k, 0);
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if(x == magic1) {
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k1 = k;
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break;
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}
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if(ntofree >= nelem(tofree)) {
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fprintf(stderr, "runtime/cgo: could not obtain pthread_keys\n");
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fprintf(stderr, "\ttried");
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for(i=0; i<ntofree; i++)
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fprintf(stderr, " %#x", (unsigned)tofree[i]);
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fprintf(stderr, "\n");
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abort();
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}
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tofree[ntofree++] = k;
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}
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/*
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* We got the key we wanted. Free the others.
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*/
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for(i=0; i<ntofree; i++)
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pthread_key_delete(tofree[i]);
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}
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void
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x_cgo_init(G *g)
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@ -74,8 +20,6 @@ x_cgo_init(G *g)
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pthread_attr_getstacksize(&attr, &size);
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g->stacklo = (uintptr)&attr - size + 4096;
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pthread_attr_destroy(&attr);
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inittls();
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}
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@ -113,10 +57,9 @@ threadentry(void *v)
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ts = *(ThreadStart*)v;
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free(v);
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if (pthread_setspecific(k1, (void*)ts.g) != 0) {
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fprintf(stderr, "runtime/cgo: pthread_setspecific failed\n");
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abort();
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}
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// Move the g pointer into the slot reserved in thread local storage.
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// Constant must match the one in cmd/link/internal/ld/sym.go.
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asm volatile("movq %0, %%gs:0x30" :: "r"(ts.g));
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crosscall_amd64(ts.fn);
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return nil;
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@ -525,15 +525,14 @@ TEXT runtime·setldt(SB),NOSPLIT,$32
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* When linking against the system libraries,
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* we use its pthread_create and let it set up %gs
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* for us. When we do that, the private storage
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* we get is not at 0(GS) but at 0x468(GS).
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* 8l rewrites 0(TLS) into 0x468(GS) for us.
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* we get is not at 0(GS) but at 0x18(GS).
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* The linker rewrites 0(TLS) into 0x18(GS) for us.
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* To accommodate that rewrite, we translate the
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* address and limit here so that 0x468(GS) maps to 0(address).
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* address here so that 0x18(GS) maps to 0(address).
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*
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* See cgo/gcc_darwin_386.c:/468 for the derivation
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* of the constant.
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* Constant must match the one in cmd/link/internal/ld/sym.go.
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*/
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SUBL $0x468, BX
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SUBL $0x18, BX
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/*
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* Must set up as USER_CTHREAD segment because
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@ -569,11 +569,10 @@ TEXT runtime·mach_semaphore_signal_all(SB),NOSPLIT,$0
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// set tls base to DI
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TEXT runtime·settls(SB),NOSPLIT,$32
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/*
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* Same as in sys_darwin_386.s:/ugliness, different constant.
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* See cgo/gcc_darwin_amd64.c for the derivation
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* of the constant.
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* Same as in sys_darwin_386.s, but a different constant.
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* Constant must match the one in cmd/link/internal/ld/sym.go.
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*/
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SUBQ $0x8a0, DI
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SUBQ $0x30, DI
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MOVL $(0x3000000+3), AX // thread_fast_set_cthread_self - machdep call #3
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SYSCALL
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