src/pkg/runtime/windows/amd64/sys.s

// Copyright 2011 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 "amd64/asm.h"

#define maxargs 12

// void runtime·asmstdcall(void *c);
TEXT runtime·asmstdcall(SB),7,$0
	// asmcgocall will put first argument into CX.
	PUSHQ	CX			// save for later
	MOVQ	wincall_fn(CX), AX
	MOVQ	wincall_args(CX), SI
	MOVQ	wincall_n(CX), CX

	// SetLastError(0).
	MOVQ	0x30(GS), DI
	MOVL	$0, 0x68(DI)

	SUBQ	$(maxargs*8), SP	// room for args

	// Fast version, do not store args on the stack.
	CMPL	CX, $4
	JLE	loadregs

	// Check we have enough room for args.
	CMPL	CX, $maxargs
	JLE	2(PC)
	INT	$3			// not enough room -> crash

	// Copy args to the stack.
	MOVQ	SP, DI
	CLD
	REP; MOVSQ
	MOVQ	SP, SI

loadregs:
	// Load first 4 args into correspondent registers.
	MOVQ	0(SI), CX
	MOVQ	8(SI), DX
	MOVQ	16(SI), R8
	MOVQ	24(SI), R9

	// Call stdcall function.
	CALL	AX

	ADDQ	$(maxargs*8), SP

	// Return result.
	POPQ	CX
	MOVQ	AX, wincall_r(CX)

	// GetLastError().
	MOVQ	0x30(GS), DI
	MOVL	0x68(DI), AX
	MOVQ	AX, wincall_err(CX)

	RET

// faster get/set last error
TEXT runtime·getlasterror(SB),7,$0
	MOVQ	0x30(GS), AX
	MOVL	0x68(AX), AX
	RET

TEXT runtime·setlasterror(SB),7,$0
	MOVL	err+0(FP), AX
	MOVQ	0x30(GS),	CX
	MOVL	AX, 0x68(CX)
	RET

// Windows runs the ctrl handler in a new thread.
TEXT runtime·ctrlhandler(SB),7,$0
	PUSHQ	BP
	MOVQ	SP, BP
	PUSHQ	BX
	PUSHQ	SI
	PUSHQ	DI
	PUSHQ	0x58(GS)
	MOVQ	SP, BX

	// setup dummy m, g
	SUBQ	$(m_fflag+4), SP	// at least space for m_fflag
	LEAQ	m_tls(SP), CX
	MOVQ	CX, 0x58(GS)
	MOVQ	SP, m(CX)
	MOVQ	SP, DX
	SUBQ	$16, SP			// space for g_stack{guard,base}
	MOVQ	SP, g(CX)
	MOVQ	SP, m_g0(DX)
	LEAQ	-8192(SP), CX
	MOVQ	CX, g_stackguard(SP)
	MOVQ	BX, g_stackbase(SP)

	PUSHQ	16(BP)
	CALL	runtime·ctrlhandler1(SB)
	POPQ	CX

	get_tls(CX)
	MOVQ	g(CX), CX
	MOVQ	g_stackbase(CX), SP
	POPQ	0x58(GS)
	POPQ	DI
	POPQ	SI
	POPQ	BX
	POPQ	BP
	RET

// Continuation of thunk function created for each callback by ../thread.c compilecallback,
// runs on Windows stack (not Go stack).
// Thunk code designed to have minimal size for it is copied many (up to thousands) times.
//
// thunk:
//	MOVQ	$fn, AX
//	PUSHQ	AX
//	MOVQ	$argsize, AX
//	PUSHQ	AX
//	MOVQ	$runtime·callbackasm, AX
//	JMP	AX
TEXT runtime·callbackasm(SB),7,$0
	// Construct args vector for cgocallback().
	// By windows/amd64 calling convention first 4 args are in CX, DX, R8, R9
	// args from the 5th on are on the stack.
	// In any case, even if function has 0,1,2,3,4 args, there is reserved
	// but uninitialized "shadow space" for the first 4 args.
	// The values are in registers.
  	MOVQ	CX, (24+0)(SP)
  	MOVQ	DX, (24+8)(SP)
  	MOVQ	R8, (24+16)(SP)
  	MOVQ	R9, (24+24)(SP)
	// 6l does not accept writing POPQs here issuing a warning "unbalanced PUSH/POP"
  	MOVQ	0(SP), DX	// POPQ DX
  	MOVQ	8(SP), AX	// POPQ AX
	ADDQ	$16, SP

	// preserve whatever's at the memory location that
	// the callback will use to store the return value
	LEAQ	8(SP), CX       // args vector, skip return address
	PUSHQ	0(CX)(DX*1)     // store 8 bytes from just after the args array
	ADDQ	$8, DX          // extend argsize by size of return value

	// DI SI BP BX R12 R13 R14 R15 registers and DF flag are preserved
	// as required by windows callback convention.
	// 6l does not allow writing many PUSHQs here issuing a warning "nosplit stack overflow"
	// the warning has no sense as this code uses os thread stack
	PUSHFQ
	SUBQ	$64, SP
	MOVQ	DI, 56(SP)
	MOVQ	SI, 48(SP)
	MOVQ	BP, 40(SP)
	MOVQ	BX, 32(SP)
	MOVQ	R12, 24(SP)
	MOVQ	R13, 16(SP)
	MOVQ	R14, 8(SP)
	MOVQ	R15, 0(SP)

	// cgocallback(void (*fn)(void*), void *frame, uintptr framesize)
	PUSHQ	DX    // uintptr framesize
	PUSHQ	CX    // void *frame
	PUSHQ	AX    // void (*fn)(void*)
	CLD
	CALL  runtime·cgocallback(SB)
	POPQ	AX
	POPQ	CX
	POPQ	DX

	// restore registers as required for windows callback
	// 6l does not allow writing many POPs here issuing a warning "nosplit stack overflow"
	MOVQ	0(SP), R15
	MOVQ	8(SP), R14
	MOVQ	16(SP), R13
	MOVQ	24(SP), R12
	MOVQ	32(SP), BX
	MOVQ	40(SP), BP
	MOVQ	48(SP), SI
	MOVQ	56(SP), DI
	ADDQ	$64, SP
	POPFQ

	MOVL	-8(CX)(DX*1), AX  // return value
	POPQ	-8(CX)(DX*1)      // restore bytes just after the args
	RET

// uint32 tstart_stdcall(M *newm);
TEXT runtime·tstart_stdcall(SB),7,$0
	// CX contains first arg newm
	MOVQ	m_g0(CX), DX		// g

	// Layout new m scheduler stack on os stack.
	MOVQ	SP, AX
	MOVQ	AX, g_stackbase(DX)
	SUBQ	$(64*1024), AX		// stack size
	MOVQ	AX, g_stackguard(DX)

	// Set up tls.
	LEAQ	m_tls(CX), SI
	MOVQ	SI, 0x58(GS)
	MOVQ	CX, m(SI)
	MOVQ	DX, g(SI)

	// Someday the convention will be D is always cleared.
	CLD

	CALL	runtime·stackcheck(SB)	// clobbers AX,CX
	CALL	runtime·mstart(SB)

	XORL	AX, AX			// return 0 == success
	RET

TEXT runtime·notok(SB),7,$0
	MOVQ	$0xf1, BP
	MOVQ	BP, (BP)
	RET

// set tls base to DI
TEXT runtime·settls(SB),7,$0
	MOVQ	DI, 0x58(GS)
	RET