cmd/go: fix -buildmode=c-archive should work on windows

Add supporting code for runtime initialization, including both
32- and 64-bit x86 architectures.

Add .ctors section on Windows to PE .o files, and INITENTRY to .ctors
section to plug in to the GCC C/C++ startup initialization mechanism.
This allows the Go runtime to initialize itself. Add .text section
symbol for .ctor relocations. Note: This is unlikely to be useful for
MSVC-based toolchains.

Fixes #13494

Change-Id: I4286a96f70e5f5228acae88eef46e2bed95813f3
Reviewed-on: https://go-review.googlesource.com/18057
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

misc/cgo/testcarchive/carchive_test.go

@@ -118,13 +118,12 @@ func goEnv(key string) string {
 }
 
 func compilemain(t *testing.T, libgo string) {
-	ccArgs := append(cc, "-o", "testp"+exeSuffix)
+	ccArgs := append(cc, "-o", "testp"+exeSuffix, "main.c")
 	if GOOS == "windows" {
-		ccArgs = append(ccArgs, "main_windows.c")
+		ccArgs = append(ccArgs, "main_windows.c", libgo, "-lntdll", "-lws2_32")
 	} else {
-		ccArgs = append(ccArgs, "main_unix.c")
+		ccArgs = append(ccArgs, "main_unix.c", libgo)
 	}
-	ccArgs = append(ccArgs, "main.c", libgo)
 	t.Log(ccArgs)
 
 	if out, err := exec.Command(ccArgs[0], ccArgs[1:]...).CombinedOutput(); err != nil {

src/cmd/dist/test.go

@@ -667,7 +667,7 @@ func (t *tester) supportedBuildmode(mode string) bool {
 		}
 		switch pair {
 		case "darwin-386", "darwin-amd64", "darwin-arm", "darwin-arm64",
-			"linux-amd64", "linux-386":
+			"linux-amd64", "linux-386", "windows-amd64", "windows-386":
 			return true
 		}
 		return false

src/cmd/link/internal/ld/data.go

@@ -1745,6 +1745,9 @@ func textaddress() {
 	sect.Align = int32(Funcalign)
 	Linklookup(Ctxt, "runtime.text", 0).Sect = sect
 	Linklookup(Ctxt, "runtime.etext", 0).Sect = sect
+	if HEADTYPE == obj.Hwindows {
+		Linklookup(Ctxt, ".text", 0).Sect = sect
+	}
 	va := uint64(INITTEXT)
 	sect.Vaddr = va
 	for sym := Ctxt.Textp; sym != nil; sym = sym.Next {
@@ -1891,6 +1894,9 @@ func address() {
 
 	xdefine("runtime.text", obj.STEXT, int64(text.Vaddr))
 	xdefine("runtime.etext", obj.STEXT, int64(text.Vaddr+text.Length))
+	if HEADTYPE == obj.Hwindows {
+		xdefine(".text", obj.STEXT, int64(text.Vaddr))
+	}
 	xdefine("runtime.rodata", obj.SRODATA, int64(rodata.Vaddr))
 	xdefine("runtime.erodata", obj.SRODATA, int64(rodata.Vaddr+rodata.Length))
 	xdefine("runtime.typelink", obj.SRODATA, int64(typelink.Vaddr))

src/cmd/link/internal/ld/lib.go

@@ -324,6 +324,12 @@ func (mode *BuildMode) Set(s string) error {
 	case "c-archive":
 		switch goos {
 		case "darwin", "linux":
+		case "windows":
+			switch goarch {
+			case "amd64", "386":
+			default:
+				return badmode()
+			}
 		default:
 			return badmode()
 		}
@@ -1020,6 +1026,15 @@ func archive() {
 	}
 
 	mayberemoveoutfile()
+
+	// Force the buffer to flush here so that external
+	// tools will see a complete file.
+	Cflush()
+	if err := coutbuf.f.Close(); err != nil {
+		Exitf("close: %v", err)
+	}
+	coutbuf.f = nil
+
 	argv := []string{extar, "-q", "-c", "-s", outfile}
 	argv = append(argv, filepath.Join(tmpdir, "go.o"))
 	argv = append(argv, hostobjCopy()...)
@@ -1890,7 +1905,6 @@ func genasmsym(put func(*LSym, string, int, int64, int64, int, *LSym)) {
 	// These symbols won't show up in the first loop below because we
 	// skip STEXT symbols. Normal STEXT symbols are emitted by walking textp.
 	s := Linklookup(Ctxt, "runtime.text", 0)
-
 	if s.Type == obj.STEXT {
 		put(s, s.Name, 'T', s.Value, s.Size, int(s.Version), nil)
 	}

src/cmd/link/internal/ld/pe.go

@@ -8,6 +8,7 @@ import (
 	"cmd/internal/obj"
 	"encoding/binary"
 	"fmt"
+	"os"
 	"sort"
 	"strconv"
 	"strings"
@@ -820,7 +821,7 @@ func perelocsect(sect *Section, first *LSym) int {
 }
 
 // peemitreloc emits relocation entries for go.o in external linking.
-func peemitreloc(text, data *IMAGE_SECTION_HEADER) {
+func peemitreloc(text, data, ctors *IMAGE_SECTION_HEADER) {
 	for Cpos()&7 != 0 {
 		Cput(0)
 	}
@@ -870,6 +871,22 @@ func peemitreloc(text, data *IMAGE_SECTION_HEADER) {
 		data.PointerToRelocations += 10 // skip the extend reloc entry
 	}
 	data.NumberOfRelocations = uint16(n - 1)
+
+	dottext := Linklookup(Ctxt, ".text", 0)
+	ctors.NumberOfRelocations = 1
+	ctors.PointerToRelocations = uint32(Cpos())
+	sectoff := ctors.VirtualAddress
+	Lputl(uint32(sectoff))
+	Lputl(uint32(dottext.Dynid))
+	switch obj.Getgoarch() {
+	default:
+		fmt.Fprintf(os.Stderr, "link: unknown architecture for PE: %q\n", obj.Getgoarch())
+		os.Exit(2)
+	case "386":
+		Wputl(IMAGE_REL_I386_DIR32)
+	case "amd64":
+		Wputl(IMAGE_REL_AMD64_ADDR64)
+	}
 }
 
 func dope() {
@@ -929,7 +946,11 @@ func writePESymTableRecords() int {
 		}
 
 		// only windows/386 requires underscore prefix on external symbols
-		if Thearch.Thechar == '8' && Linkmode == LinkExternal && (s.Type == obj.SHOSTOBJ || s.Attr.CgoExport()) && s.Name == s.Extname {
+		if Thearch.Thechar == '8' &&
+			Linkmode == LinkExternal &&
+			(s.Type != obj.SDYNIMPORT || s.Attr.CgoExport()) &&
+			s.Name == s.Extname &&
+			s.Name != "_main" {
 			s.Name = "_" + s.Name
 		}
 
@@ -984,6 +1005,11 @@ func writePESymTableRecords() int {
 				put(s, s.Name, 'U', 0, int64(Thearch.Ptrsize), 0, nil)
 			}
 		}
+
+		s := Linklookup(Ctxt, ".text", 0)
+		if s.Type == obj.STEXT {
+			put(s, s.Name, 'T', s.Value, s.Size, int(s.Version), nil)
+		}
 	}
 
 	genasmsym(put)
@@ -1066,6 +1092,42 @@ func addpersrc() {
 	dd[IMAGE_DIRECTORY_ENTRY_RESOURCE].Size = h.VirtualSize
 }
 
+func addinitarray() (c *IMAGE_SECTION_HEADER) {
+	// The size below was determined by the specification for array relocations,
+	// and by observing what GCC writes here. If the initarray section grows to
+	// contain more than one constructor entry, the size will need to be 8 * constructor_count.
+	// However, the entire Go runtime is initialized from just one function, so it is unlikely
+	// that this will need to grow in the future.
+	var size int
+	switch obj.Getgoarch() {
+	default:
+		fmt.Fprintf(os.Stderr, "link: unknown architecture for PE: %q\n", obj.Getgoarch())
+		os.Exit(2)
+	case "386":
+		size = 4
+	case "amd64":
+		size = 8
+	}
+
+	c = addpesection(".ctors", size, size)
+	c.Characteristics = IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
+	c.SizeOfRawData = uint32(size)
+
+	Cseek(int64(c.PointerToRawData))
+	chksectoff(c, Cpos())
+	init_entry := Linklookup(Ctxt, INITENTRY, 0)
+	addr := uint64(init_entry.Value) - init_entry.Sect.Vaddr
+
+	switch obj.Getgoarch() {
+	case "386":
+		Lputl(uint32(addr))
+	case "amd64":
+		Vputl(addr)
+	}
+
+	return c
+}
+
 func Asmbpe() {
 	switch Thearch.Thechar {
 	default:
@@ -1087,6 +1149,7 @@ func Asmbpe() {
 	textsect = pensect
 
 	var d *IMAGE_SECTION_HEADER
+	var c *IMAGE_SECTION_HEADER
 	if Linkmode != LinkExternal {
 		d = addpesection(".data", int(Segdata.Length), int(Segdata.Filelen))
 		d.Characteristics = IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE
@@ -1102,6 +1165,8 @@ func Asmbpe() {
 		b.Characteristics = IMAGE_SCN_CNT_UNINITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE | IMAGE_SCN_ALIGN_32BYTES
 		b.PointerToRawData = 0
 		bsssect = pensect
+
+		c = addinitarray()
 	}
 
 	if Debug['s'] == 0 {
@@ -1116,7 +1181,7 @@ func Asmbpe() {
 	addpesymtable()
 	addpersrc()
 	if Linkmode == LinkExternal {
-		peemitreloc(t, d)
+		peemitreloc(t, d, c)
 	}
 
 	fh.NumberOfSections = uint16(pensect)

src/runtime/cgo/gcc_libinit_windows.c

@@ -2,21 +2,89 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build cgo
+#define WIN64_LEAN_AND_MEAN
+#include <windows.h>
+#include <process.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 
+static volatile long runtime_init_once_gate = 0;
+static volatile long runtime_init_once_done = 0;
+
+static CRITICAL_SECTION runtime_init_cs;
+
+static HANDLE runtime_init_wait;
+static int runtime_init_done;
+
+// Pre-initialize the runtime synchronization objects
 void
-x_cgo_sys_thread_create(void* (*func)(void*), void* arg) {
+_cgo_preinit_init() {
-	fprintf(stderr, "x_cgo_sys_thread_create not implemented");
+	 runtime_init_wait = CreateEvent(NULL, TRUE, FALSE, NULL);
-	abort();
+	 if (runtime_init_wait == NULL) {
+		fprintf(stderr, "runtime: failed to create runtime initialization wait event.\n");
+		abort();
+	 }
+
+	 InitializeCriticalSection(&runtime_init_cs);
+}
+
+// Make sure that the preinit sequence has run.
+void
+_cgo_maybe_run_preinit() {
+	 if (!InterlockedExchangeAdd(&runtime_init_once_done, 0)) {
+			if (InterlockedIncrement(&runtime_init_once_gate) == 1) {
+				 _cgo_preinit_init();
+				 InterlockedIncrement(&runtime_init_once_done);
+			} else {
+				 // Decrement to avoid overflow.
+				 InterlockedDecrement(&runtime_init_once_gate);
+				 while(!InterlockedExchangeAdd(&runtime_init_once_done, 0)) {
+						Sleep(0);
+				 }
+			}
+	 }
+}
+
+void
+x_cgo_sys_thread_create(void (*func)(void*), void* arg) {
+	uintptr_t thandle;
+
+	thandle = _beginthread(func, 0, arg);
+	if(thandle == -1) {
+		fprintf(stderr, "runtime: failed to create new OS thread (%d)\n", errno);
+		abort();
+	}
+}
+
+int
+_cgo_is_runtime_initialized() {
+	 EnterCriticalSection(&runtime_init_cs);
+	 int status = runtime_init_done;
+	 LeaveCriticalSection(&runtime_init_cs);
+	 return status;
 }
 
 void
 _cgo_wait_runtime_init_done() {
-	// TODO(spetrovic): implement this method.
+	 _cgo_maybe_run_preinit();
+	while (!_cgo_is_runtime_initialized()) {
+			WaitForSingleObject(runtime_init_wait, INFINITE);
+	}
 }
 
 void
 x_cgo_notify_runtime_init_done(void* dummy) {
-	// TODO(spetrovic): implement this method.
+	 _cgo_maybe_run_preinit();
-}
+
+	 EnterCriticalSection(&runtime_init_cs);
+	runtime_init_done = 1;
+	 LeaveCriticalSection(&runtime_init_cs);
+
+	 if (!SetEvent(runtime_init_wait)) {
+		fprintf(stderr, "runtime: failed to signal runtime initialization complete.\n");
+		abort();
+	}
+}
+

src/runtime/os1_windows.go

@@ -396,8 +396,11 @@ func semacreate(mp *m) {
 	mp.waitsema = stdcall4(_CreateEventA, 0, 0, 0, 0)
 }
 
-// May run with m.p==nil, so write barriers are not allowed.
+// May run with m.p==nil, so write barriers are not allowed. This
-//go:nowritebarrier
+// function is called by newosproc0, so it is also required to
+// operate without stack guards.
+//go:nowritebarrierc
+//go:nosplit
 func newosproc(mp *m, stk unsafe.Pointer) {
 	const _STACK_SIZE_PARAM_IS_A_RESERVATION = 0x00010000
 	thandle := stdcall6(_CreateThread, 0, 0x20000,
@@ -409,6 +412,15 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 	}
 }
 
+// Used by the C library build mode. On Linux this function would allocate a
+// stack, but that's not necessary for Windows. No stack guards are present
+// and the GC has not been initialized, so write barriers will fail.
+//go:nowritebarrierc
+//go:nosplit
+func newosproc0(mp *m, stk unsafe.Pointer) {
+	newosproc(mp, stk)
+}
+
 // Called to initialize a new m (including the bootstrap m).
 // Called on the parent thread (main thread in case of bootstrap), can allocate memory.
 func mpreinit(mp *m) {

src/runtime/rt0_windows_386.s

@@ -12,5 +12,39 @@ TEXT _rt0_386_windows(SB),NOSPLIT,$12
 	MOVL	$-1, 0(SP) // return PC for main
 	JMP	_main(SB)
 
+// When building with -buildmode=(c-shared or c-archive), this
+// symbol is called. For dynamic libraries it is called when the
+// library is loaded. For static libraries it is called when the
+// final executable starts, during the C runtime initialization
+// phase.
+TEXT _rt0_386_windows_lib(SB),NOSPLIT,$0x1C
+	MOVL	BP, 0x08(SP)
+	MOVL	BX, 0x0C(SP)
+	MOVL	AX, 0x10(SP)
+	MOVL  CX, 0x14(SP)
+	MOVL  DX, 0x18(SP)
+
+	// Create a new thread to do the runtime initialization and return.
+	MOVL	_cgo_sys_thread_create(SB), AX
+	MOVL	$_rt0_386_windows_lib_go(SB), 0x00(SP)
+	MOVL	$0, 0x04(SP)
+
+	 // Top two items on the stack are passed to _cgo_sys_thread_create
+	 // as parameters. This is the calling convention on 32-bit Windows.
+	CALL	AX
+
+	MOVL	0x08(SP), BP
+	MOVL	0x0C(SP), BX
+	MOVL	0x10(SP), AX
+	MOVL	0x14(SP), CX
+	MOVL	0x18(SP), DX
+	RET
+
+TEXT _rt0_386_windows_lib_go(SB),NOSPLIT,$0
+	MOVL  $0, DI
+	MOVL	$0, SI
+	MOVL	$runtime·rt0_go(SB), AX
+	JMP	AX
+
 TEXT _main(SB),NOSPLIT,$0
 	JMP	runtime·rt0_go(SB)

src/runtime/rt0_windows_amd64.s

@@ -12,6 +12,37 @@ TEXT _rt0_amd64_windows(SB),NOSPLIT,$-8
 	MOVQ	$main(SB), AX
 	JMP	AX
 
+// When building with -buildmode=(c-shared or c-archive), this
+// symbol is called. For dynamic libraries it is called when the
+// library is loaded. For static libraries it is called when the
+// final executable starts, during the C runtime initialization
+// phase.
+TEXT _rt0_amd64_windows_lib(SB),NOSPLIT,$0x28
+	MOVQ	BP, 0x00(SP)
+	MOVQ	BX, 0x08(SP)
+	MOVQ	AX, 0x10(SP)
+	MOVQ  CX, 0x18(SP)
+	MOVQ  DX, 0x20(SP)
+
+	// Create a new thread to do the runtime initialization and return.
+	MOVQ	_cgo_sys_thread_create(SB), AX
+	MOVQ	$_rt0_amd64_windows_lib_go(SB), CX
+	MOVQ	$0, DX
+	CALL	AX
+
+	MOVQ	0x00(SP), BP
+	MOVQ	0x08(SP), BX
+	MOVQ	0x10(SP), AX
+	MOVQ	0x18(SP), CX
+	MOVQ	0x20(SP), DX
+	RET
+
+TEXT _rt0_amd64_windows_lib_go(SB),NOSPLIT,$0
+	MOVQ  $0, DI
+	MOVQ	$0, SI
+	MOVQ	$runtime·rt0_go(SB), AX
+	JMP	AX
+
 TEXT main(SB),NOSPLIT,$-8
 	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX

src/runtime/testdata/testprogcgo/threadpanic_windows.c

@@ -2,12 +2,13 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+#include <process.h>
 #include <stdlib.h>
 #include <stdio.h>
 
 void gopanic(void);
 
-static void*
+static unsigned int
 die(void* x)
 {
 	gopanic();