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// Copyright 2014 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.
package runtime
import (
"internal/abi"
"runtime/internal/sys"
"unsafe"
)
// cbs stores all registered Go callbacks.
var cbs struct {
lock mutex
ctxt [cb_max]winCallback
index map[winCallbackKey]int
n int
}
// winCallback records information about a registered Go callback.
type winCallback struct {
fn *funcval // Go function
retPop uintptr // For 386 cdecl, how many bytes to pop on return
// abiMap specifies how to translate from a C frame to a Go
// frame. This does not specify how to translate back because
// the result is always a uintptr. If the C ABI is fastcall,
// this assumes the four fastcall registers were first spilled
// to the shadow space.
abiMap []abiPart
// retOffset is the offset of the uintptr-sized result in the Go
// frame.
retOffset uintptr
}
// abiPart encodes a step in translating between calling ABIs.
type abiPart struct {
src, dst uintptr
len uintptr
}
func (a *abiPart) tryMerge(b abiPart) bool {
if a.src+a.len == b.src && a.dst+a.len == b.dst {
a.len += b.len
return true
}
return false
}
type winCallbackKey struct {
fn *funcval
cdecl bool
}
func callbackasm()
// callbackasmAddr returns address of runtime.callbackasm
// function adjusted by i.
// On x86 and amd64, runtime.callbackasm is a series of CALL instructions,
// and we want callback to arrive at
// correspondent call instruction instead of start of
// runtime.callbackasm.
// On ARM, runtime.callbackasm is a series of mov and branch instructions.
// R12 is loaded with the callback index. Each entry is two instructions,
// hence 8 bytes.
func callbackasmAddr(i int) uintptr {
var entrySize int
switch GOARCH {
default:
panic("unsupported architecture")
case "386", "amd64":
entrySize = 5
case "arm", "arm64":
// On ARM and ARM64, each entry is a MOV instruction
// followed by a branch instruction
entrySize = 8
}
return funcPC(callbackasm) + uintptr(i*entrySize)
}
const callbackMaxFrame = 64 * sys.PtrSize
// compileCallback converts a Go function fn into a C function pointer
// that can be passed to Windows APIs.
//
// On 386, if cdecl is true, the returned C function will use the
// cdecl calling convention; otherwise, it will use stdcall. On amd64,
// it always uses fastcall. On arm, it always uses the ARM convention.
//
//go:linkname compileCallback syscall.compileCallback
func compileCallback(fn eface, cdecl bool) (code uintptr) {
if GOARCH != "386" {
// cdecl is only meaningful on 386.
cdecl = false
}
if fn._type == nil || (fn._type.kind&kindMask) != kindFunc {
panic("compileCallback: expected function with one uintptr-sized result")
}
ft := (*functype)(unsafe.Pointer(fn._type))
// Check arguments and construct ABI translation.
var abiMap []abiPart
var src, dst uintptr
for _, t := range ft.in() {
if t.size > sys.PtrSize {
// We don't support this right now. In
// stdcall/cdecl, 64-bit ints and doubles are
// passed as two words (little endian); and
// structs are pushed on the stack. In
// fastcall, arguments larger than the word
// size are passed by reference. On arm,
// 8-byte aligned arguments round up to the
// next even register and can be split across
// registers and the stack.
panic("compileCallback: argument size is larger than uintptr")
}
if k := t.kind & kindMask; GOARCH != "386" && (k == kindFloat32 || k == kindFloat64) {
// In fastcall, floating-point arguments in
// the first four positions are passed in
// floating-point registers, which we don't
// currently spill. arm passes floating-point
// arguments in VFP registers, which we also
// don't support.
// So basically we only support 386.
panic("compileCallback: float arguments not supported")
}
// The Go ABI aligns arguments.
dst = alignUp(dst, uintptr(t.align))
// In the C ABI, we're already on a word boundary.
// Also, sub-word-sized fastcall register arguments
// are stored to the least-significant bytes of the
// argument word and all supported Windows
// architectures are little endian, so src is already
// pointing to the right place for smaller arguments.
// The same is true on arm.
// Copy just the size of the argument. Note that this
// could be a small by-value struct, but C and Go
// struct layouts are compatible, so we can copy these
// directly, too.
part := abiPart{src, dst, t.size}
// Add this step to the adapter.
if len(abiMap) == 0 || !abiMap[len(abiMap)-1].tryMerge(part) {
abiMap = append(abiMap, part)
}
// cdecl, stdcall, fastcall, and arm pad arguments to word size.
// TODO(rsc): On arm and arm64 do we need to skip the caller's saved LR?
src += sys.PtrSize
// The Go ABI packs arguments.
dst += t.size
}
// The Go ABI aligns the result to the word size. src is
// already aligned.
dst = alignUp(dst, sys.PtrSize)
retOffset := dst
if len(ft.out()) != 1 {
panic("compileCallback: expected function with one uintptr-sized result")
}
if ft.out()[0].size != sys.PtrSize {
panic("compileCallback: expected function with one uintptr-sized result")
}
if k := ft.out()[0].kind & kindMask; k == kindFloat32 || k == kindFloat64 {
// In cdecl and stdcall, float results are returned in
// ST(0). In fastcall, they're returned in XMM0.
// Either way, it's not AX.
panic("compileCallback: float results not supported")
}
// Make room for the uintptr-sized result.
dst += sys.PtrSize
if dst > callbackMaxFrame {
panic("compileCallback: function argument frame too large")
}
// For cdecl, the callee is responsible for popping its
// arguments from the C stack.
var retPop uintptr
if cdecl {
retPop = src
}
key := winCallbackKey{(*funcval)(fn.data), cdecl}
lock(&cbs.lock) // We don't unlock this in a defer because this is used from the system stack.
// Check if this callback is already registered.
if n, ok := cbs.index[key]; ok {
unlock(&cbs.lock)
return callbackasmAddr(n)
}
// Register the callback.
if cbs.index == nil {
cbs.index = make(map[winCallbackKey]int)
}
n := cbs.n
if n >= len(cbs.ctxt) {
unlock(&cbs.lock)
throw("too many callback functions")
}
c := winCallback{key.fn, retPop, abiMap, retOffset}
cbs.ctxt[n] = c
cbs.index[key] = n
cbs.n++
unlock(&cbs.lock)
return callbackasmAddr(n)
}
type callbackArgs struct {
index uintptr
// args points to the argument block.
//
// For cdecl and stdcall, all arguments are on the stack.
//
// For fastcall, the trampoline spills register arguments to
// the reserved spill slots below the stack arguments,
// resulting in a layout equivalent to stdcall.
//
// For arm, the trampoline stores the register arguments just
// below the stack arguments, so again we can treat it as one
// big stack arguments frame.
args unsafe.Pointer
// Below are out-args from callbackWrap
result uintptr
retPop uintptr // For 386 cdecl, how many bytes to pop on return
}
// callbackWrap is called by callbackasm to invoke a registered C callback.
func callbackWrap(a *callbackArgs) {
c := cbs.ctxt[a.index]
a.retPop = c.retPop
// Convert from C to Go ABI.
var frame [callbackMaxFrame]byte
goArgs := unsafe.Pointer(&frame)
for _, part := range c.abiMap {
memmove(add(goArgs, part.dst), add(a.args, part.src), part.len)
}
// Even though this is copying back results, we can pass a nil
// type because those results must not require write barriers.
//
// Pass a dummy RegArgs for now.
// TODO(mknyszek): Pass arguments in registers.
var regs abi.RegArgs
reflectcall(nil, unsafe.Pointer(c.fn), noescape(goArgs), uint32(c.retOffset)+sys.PtrSize, uint32(c.retOffset), uint32(c.retOffset)+sys.PtrSize, &regs)
// Extract the result.
a.result = *(*uintptr)(unsafe.Pointer(&frame[c.retOffset]))
}
const _LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800
// When available, this function will use LoadLibraryEx with the filename
// parameter and the important SEARCH_SYSTEM32 argument. But on systems that
// do not have that option, absoluteFilepath should contain a fallback
// to the full path inside of system32 for use with vanilla LoadLibrary.
//go:linkname syscall_loadsystemlibrary syscall.loadsystemlibrary
//go:nosplit
//go:cgo_unsafe_args
func syscall_loadsystemlibrary(filename *uint16, absoluteFilepath *uint16) (handle, err uintptr) {
lockOSThread()
c := &getg().m.syscall
if useLoadLibraryEx {
c.fn = getLoadLibraryEx()
c.n = 3
args := struct {
lpFileName *uint16
hFile uintptr // always 0
flags uint32
}{filename, 0, _LOAD_LIBRARY_SEARCH_SYSTEM32}
c.args = uintptr(noescape(unsafe.Pointer(&args)))
} else {
c.fn = getLoadLibrary()
c.n = 1
c.args = uintptr(noescape(unsafe.Pointer(&absoluteFilepath)))
}
cgocall(asmstdcallAddr, unsafe.Pointer(c))
handle = c.r1
if handle == 0 {
err = c.err
}
unlockOSThread() // not defer'd after the lockOSThread above to save stack frame size.
return
}
//go:linkname syscall_loadlibrary syscall.loadlibrary
//go:nosplit
//go:cgo_unsafe_args
func syscall_loadlibrary(filename *uint16) (handle, err uintptr) {
lockOSThread()
defer unlockOSThread()
c := &getg().m.syscall
c.fn = getLoadLibrary()
c.n = 1
c.args = uintptr(noescape(unsafe.Pointer(&filename)))
cgocall(asmstdcallAddr, unsafe.Pointer(c))
handle = c.r1
if handle == 0 {
err = c.err
}
return
}
//go:linkname syscall_getprocaddress syscall.getprocaddress
//go:nosplit
//go:cgo_unsafe_args
func syscall_getprocaddress(handle uintptr, procname *byte) (outhandle, err uintptr) {
lockOSThread()
defer unlockOSThread()
c := &getg().m.syscall
c.fn = getGetProcAddress()
c.n = 2
c.args = uintptr(noescape(unsafe.Pointer(&handle)))
cgocall(asmstdcallAddr, unsafe.Pointer(c))
outhandle = c.r1
if outhandle == 0 {
err = c.err
}
return
}
//go:linkname syscall_Syscall syscall.Syscall
//go:nosplit
//go:cgo_unsafe_args
func syscall_Syscall(fn, nargs, a1, a2, a3 uintptr) (r1, r2, err uintptr) {
lockOSThread()
defer unlockOSThread()
c := &getg().m.syscall
c.fn = fn
c.n = nargs
c.args = uintptr(noescape(unsafe.Pointer(&a1)))
cgocall(asmstdcallAddr, unsafe.Pointer(c))
return c.r1, c.r2, c.err
}
//go:linkname syscall_Syscall6 syscall.Syscall6
//go:nosplit
//go:cgo_unsafe_args
func syscall_Syscall6(fn, nargs, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr) {
lockOSThread()
defer unlockOSThread()
c := &getg().m.syscall
c.fn = fn
c.n = nargs
c.args = uintptr(noescape(unsafe.Pointer(&a1)))
cgocall(asmstdcallAddr, unsafe.Pointer(c))
return c.r1, c.r2, c.err
}
//go:linkname syscall_Syscall9 syscall.Syscall9
//go:nosplit
//go:cgo_unsafe_args
func syscall_Syscall9(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2, err uintptr) {
lockOSThread()
defer unlockOSThread()
c := &getg().m.syscall
c.fn = fn
c.n = nargs
c.args = uintptr(noescape(unsafe.Pointer(&a1)))
cgocall(asmstdcallAddr, unsafe.Pointer(c))
return c.r1, c.r2, c.err
}
//go:linkname syscall_Syscall12 syscall.Syscall12
//go:nosplit
//go:cgo_unsafe_args
func syscall_Syscall12(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12 uintptr) (r1, r2, err uintptr) {
lockOSThread()
defer unlockOSThread()
c := &getg().m.syscall
c.fn = fn
c.n = nargs
c.args = uintptr(noescape(unsafe.Pointer(&a1)))
cgocall(asmstdcallAddr, unsafe.Pointer(c))
return c.r1, c.r2, c.err
}
//go:linkname syscall_Syscall15 syscall.Syscall15
//go:nosplit
//go:cgo_unsafe_args
func syscall_Syscall15(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15 uintptr) (r1, r2, err uintptr) {
lockOSThread()
defer unlockOSThread()
c := &getg().m.syscall
c.fn = fn
c.n = nargs
c.args = uintptr(noescape(unsafe.Pointer(&a1)))
cgocall(asmstdcallAddr, unsafe.Pointer(c))
return c.r1, c.r2, c.err
}
//go:linkname syscall_Syscall18 syscall.Syscall18
//go:nosplit
//go:cgo_unsafe_args
func syscall_Syscall18(fn, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18 uintptr) (r1, r2, err uintptr) {
lockOSThread()
defer unlockOSThread()
c := &getg().m.syscall
c.fn = fn
c.n = nargs
c.args = uintptr(noescape(unsafe.Pointer(&a1)))
cgocall(asmstdcallAddr, unsafe.Pointer(c))
return c.r1, c.r2, c.err
}