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cmd/link,runtime/cgo: enable PT_TLS generation on OpenBSD
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OpenBSD 6.0 and later have support for PT_TLS in ld.so(1). Now that OpenBSD
6.1 has been released, OpenBSD 5.9 is no longer officially supported and Go
can start generating PT_TLS for OpenBSD cgo binaries. This also allows us
to remove the workarounds in the OpenBSD cgo runtime.

This change also removes the environ and progname exports - these are now
provided directly by ld.so(1) itself.

Fixes #19932

Change-Id: I42e75ef9feb5dcd4696add5233497e3cbc48ad52
Reviewed-on: https://go-review.googlesource.com/40331
Reviewed-by: Ian Lance Taylor <iant@golang.org>
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@4a6f656c
4a6f656c committed Apr 11, 2017
1 parent 2122fc6 commit 9417c02
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Showing 8 changed files with 25 additions and 380 deletions.
6 changes: 3 additions & 3 deletions src/cmd/link/internal/ld/data.go
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Original file line number Diff line number Diff line change
Expand Up @@ -449,7 +449,7 @@ func relocsym(ctxt *Link, s *Symbol) {
case obj.R_TLS_LE:
isAndroidX86 := obj.GOOS == "android" && (SysArch.InFamily(sys.AMD64, sys.I386))

if Linkmode == LinkExternal && Iself && Headtype != obj.Hopenbsd && !isAndroidX86 {
if Linkmode == LinkExternal && Iself && !isAndroidX86 {
r.Done = 0
if r.Sym == nil {
r.Sym = ctxt.Tlsg
Expand Down Expand Up @@ -483,7 +483,7 @@ func relocsym(ctxt *Link, s *Symbol) {
case obj.R_TLS_IE:
isAndroidX86 := obj.GOOS == "android" && (SysArch.InFamily(sys.AMD64, sys.I386))

if Linkmode == LinkExternal && Iself && Headtype != obj.Hopenbsd && !isAndroidX86 {
if Linkmode == LinkExternal && Iself && !isAndroidX86 {
r.Done = 0
if r.Sym == nil {
r.Sym = ctxt.Tlsg
Expand Down Expand Up @@ -1570,7 +1570,7 @@ func (ctxt *Link) dodata() {

if len(data[obj.STLSBSS]) > 0 {
var sect *Section
if Iself && (Linkmode == LinkExternal || !*FlagD) && Headtype != obj.Hopenbsd {
if Iself && (Linkmode == LinkExternal || !*FlagD) {
sect = addsection(&Segdata, ".tbss", 06)
sect.Align = int32(SysArch.PtrSize)
sect.Vaddr = 0
Expand Down
40 changes: 16 additions & 24 deletions src/cmd/link/internal/ld/elf.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1894,14 +1894,11 @@ func (ctxt *Link) doelf() {
Addstring(shstrtab, ".bss")
Addstring(shstrtab, ".noptrbss")

// generate .tbss section (except for OpenBSD where it's not supported)
// for dynamic internal linker or external linking, so that various
// binutils could correctly calculate PT_TLS size.
// see https://golang.org/issue/5200.
if Headtype != obj.Hopenbsd {
if !*FlagD || Linkmode == LinkExternal {
Addstring(shstrtab, ".tbss")
}
// generate .tbss section for dynamic internal linker or external
// linking, so that various binutils could correctly calculate
// PT_TLS size. See https://golang.org/issue/5200.
if !*FlagD || Linkmode == LinkExternal {
Addstring(shstrtab, ".tbss")
}
if Headtype == obj.Hnetbsd {
Addstring(shstrtab, ".note.netbsd.ident")
Expand Down Expand Up @@ -2525,24 +2522,19 @@ func Asmbelf(ctxt *Link, symo int64) {
/*
* Thread-local storage segment (really just size).
*/
// Do not emit PT_TLS for OpenBSD since ld.so(1) does
// not currently support it. This is handled
// appropriately in runtime/cgo.
if Headtype != obj.Hopenbsd {
tlssize := uint64(0)
for sect := Segdata.Sect; sect != nil; sect = sect.Next {
if sect.Name == ".tbss" {
tlssize = sect.Length
}
}
if tlssize != 0 {
ph := newElfPhdr()
ph.type_ = PT_TLS
ph.flags = PF_R
ph.memsz = tlssize
ph.align = uint64(SysArch.RegSize)
tlssize := uint64(0)
for sect := Segdata.Sect; sect != nil; sect = sect.Next {
if sect.Name == ".tbss" {
tlssize = sect.Length
}
}
if tlssize != 0 {
ph := newElfPhdr()
ph.type_ = PT_TLS
ph.flags = PF_R
ph.memsz = tlssize
ph.align = uint64(SysArch.RegSize)
}
}

if Headtype == obj.Hlinux {
Expand Down
2 changes: 1 addition & 1 deletion src/cmd/link/internal/ld/lib.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1971,7 +1971,7 @@ func genasmsym(ctxt *Link, put func(*Link, *Symbol, string, SymbolType, int64, *
put(ctxt, s, s.Extname, UndefinedSym, 0, nil)

case obj.STLSBSS:
if Linkmode == LinkExternal && Headtype != obj.Hopenbsd {
if Linkmode == LinkExternal {
put(ctxt, s, s.Name, TLSSym, Symaddr(s), s.Gotype)
}
}
Expand Down
2 changes: 1 addition & 1 deletion src/runtime/cgo/gcc_libinit.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
// license that can be found in the LICENSE file.

// +build cgo
// +build darwin dragonfly freebsd linux netbsd solaris
// +build darwin dragonfly freebsd linux netbsd openbsd solaris

#include <pthread.h>
#include <errno.h>
Expand Down
74 changes: 0 additions & 74 deletions src/runtime/cgo/gcc_libinit_openbsd.c
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Original file line number Diff line number Diff line change
@@ -1,74 +0,0 @@
// Copyright 2015 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 <errno.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include "libcgo.h"

// The context function, used when tracing back C calls into Go.
static void (*cgo_context_function)(struct context_arg*);

void
x_cgo_sys_thread_create(void* (*func)(void*), void* arg) {
fprintf(stderr, "x_cgo_sys_thread_create not implemented");
abort();
}

uintptr_t
_cgo_wait_runtime_init_done() {
void (*pfn)(struct context_arg*);

// TODO(spetrovic): implement this method.

pfn = _cgo_get_context_function();
if (pfn != nil) {
struct context_arg arg;

arg.Context = 0;
(*pfn)(&arg);
return arg.Context;
}
return 0;
}

void
x_cgo_notify_runtime_init_done(void* dummy) {
// TODO(spetrovic): implement this method.
}

// Sets the context function to call to record the traceback context
// when calling a Go function from C code. Called from runtime.SetCgoTraceback.
void x_cgo_set_context_function(void (*context)(struct context_arg*)) {
// TODO(iant): Needs synchronization.
cgo_context_function = context;
}

// Gets the context function.
void (*(_cgo_get_context_function(void)))(struct context_arg*) {
return cgo_context_function;
}

// _cgo_try_pthread_create retries sys_pthread_create if it fails with
// EAGAIN.
int
_cgo_openbsd_try_pthread_create(int (*sys_pthread_create)(pthread_t*, const pthread_attr_t*, void* (*)(void*), void*),
pthread_t* thread, const pthread_attr_t* attr, void* (*pfn)(void*), void* arg) {
int tries;
int err;
struct timespec ts;

for (tries = 0; tries < 100; tries++) {
err = sys_pthread_create(thread, attr, pfn, arg);
if (err != EAGAIN) {
return err;
}
ts.tv_sec = 0;
ts.tv_nsec = (tries + 1) * 1000 * 1000; // Milliseconds.
nanosleep(&ts, nil);
}
return EAGAIN;
}
133 changes: 1 addition & 132 deletions src/runtime/cgo/gcc_openbsd_386.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,6 @@
// 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>
Expand All @@ -14,125 +12,6 @@
static void* threadentry(void*);
static void (*setg_gcc)(void*);

// TCB_SIZE is sizeof(struct thread_control_block), as defined in
// /usr/src/lib/librthread/tcb.h on OpenBSD 5.9 and earlier.
#define TCB_SIZE (4 * sizeof(void *))

// TIB_SIZE is sizeof(struct tib), as defined in
// /usr/include/tib.h on OpenBSD 6.0 and later.
#define TIB_SIZE (4 * sizeof(void *) + 6 * sizeof(int))

// TLS_SIZE is the size of TLS needed for Go.
#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,
void *(*start_routine)(void *), void *arg);

struct thread_args {
void *(*func)(void *);
void *arg;
};

static int has_tib = 0;

static void
tcb_fixup(int mainthread)
{
void *tls, *newtcb, *oldtcb;
size_t tls_size, tcb_size;

// TODO(jsing): Remove once OpenBSD 6.1 is released and OpenBSD 5.9 is
// no longer supported.

// The OpenBSD ld.so(1) does not currently support PT_TLS. As a result,
// we need to allocate our own TLS space while preserving the existing
// TCB or TIB that has been setup via librthread.

tcb_size = has_tib ? TIB_SIZE : TCB_SIZE;
tls_size = TLS_SIZE + tcb_size;
tls = malloc(tls_size);
if(tls == NULL)
abort();

// The signal trampoline expects the TLS slots to be zeroed.
bzero(tls, TLS_SIZE);

oldtcb = __get_tcb();
newtcb = tls + TLS_SIZE;
bcopy(oldtcb, newtcb, tcb_size);
if(has_tib) {
// Fix up self pointer.
*(uintptr_t *)(newtcb) = (uintptr_t)newtcb;
}
__set_tcb(newtcb);

// NOTE(jsing, minux): we can't free oldtcb without causing double-free
// problem. so newtcb will be memory leaks. Get rid of this when OpenBSD
// has proper support for PT_TLS.
}

static void *
thread_start_wrapper(void *arg)
{
struct thread_args args = *(struct thread_args *)arg;

free(arg);
tcb_fixup(0);

return args.func(args.arg);
}

static void init_pthread_wrapper(void) {
void *handle;

// Locate symbol for the system pthread_create function.
handle = dlopen("libpthread.so", RTLD_LAZY);
if(handle == NULL) {
fprintf(stderr, "runtime/cgo: dlopen failed to load libpthread: %s\n", dlerror());
abort();
}
sys_pthread_create = dlsym(handle, "pthread_create");
if(sys_pthread_create == NULL) {
fprintf(stderr, "runtime/cgo: dlsym failed to find pthread_create: %s\n", dlerror());
abort();
}
// _rthread_init is hidden in OpenBSD librthread that has TIB.
if(dlsym(handle, "_rthread_init") == NULL) {
has_tib = 1;
}
dlclose(handle);
}

static pthread_once_t init_pthread_wrapper_once = PTHREAD_ONCE_INIT;

int
pthread_create(pthread_t *thread, const pthread_attr_t *attr,
void *(*start_routine)(void *), void *arg)
{
struct thread_args *p;

// we must initialize our wrapper in pthread_create, because it is valid to call
// pthread_create in a static constructor, and in fact, our test for issue 9456
// does just that.
if(pthread_once(&init_pthread_wrapper_once, init_pthread_wrapper) != 0) {
fprintf(stderr, "runtime/cgo: failed to initialize pthread_create wrapper\n");
abort();
}

p = malloc(sizeof(*p));
if(p == NULL) {
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, void (*setg)(void*))
{
Expand All @@ -144,16 +23,8 @@ x_cgo_init(G *g, void (*setg)(void*))
pthread_attr_getstacksize(&attr, &size);
g->stacklo = (uintptr)&attr - size + 4096;
pthread_attr_destroy(&attr);

if(pthread_once(&init_pthread_wrapper_once, init_pthread_wrapper) != 0) {
fprintf(stderr, "runtime/cgo: failed to initialize pthread_create wrapper\n");
abort();
}

tcb_fixup(1);
}


void
_cgo_sys_thread_start(ThreadStart *ts)
{
Expand All @@ -171,7 +42,7 @@ _cgo_sys_thread_start(ThreadStart *ts)

// Leave stacklo=0 and set stackhi=size; mstack will do the rest.
ts->g->stackhi = size;
err = _cgo_openbsd_try_pthread_create(sys_pthread_create, &p, &attr, threadentry, ts);
err = _cgo_try_pthread_create(&p, &attr, threadentry, ts);

pthread_sigmask(SIG_SETMASK, &oset, nil);

Expand All @@ -186,8 +57,6 @@ threadentry(void *v)
{
ThreadStart ts;

tcb_fixup(0);

ts = *(ThreadStart*)v;
free(v);

Expand Down
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