// Copyright 2009 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 "go_asm.h"
#include "go_tls.h"
#include "textflag.h"

// void runtime·asmstdcall(void *c);
TEXT runtime·asmstdcall<ABIInternal>(SB),NOSPLIT,$0
	MOVL	fn+0(FP), BX

	// SetLastError(0).
	MOVL	$0, 0x34(FS)

	// Copy args to the stack.
	MOVL	SP, BP
	MOVL	libcall_n(BX), CX	// words
	MOVL	CX, AX
	SALL	$2, AX
	SUBL	AX, SP			// room for args
	MOVL	SP, DI
	MOVL	libcall_args(BX), SI
	CLD
	REP; MOVSL

	// Call stdcall or cdecl function.
	// DI SI BP BX are preserved, SP is not
	CALL	libcall_fn(BX)
	MOVL	BP, SP

	// Return result.
	MOVL	fn+0(FP), BX
	MOVL	AX, libcall_r1(BX)
	MOVL	DX, libcall_r2(BX)

	// GetLastError().
	MOVL	0x34(FS), AX
	MOVL	AX, libcall_err(BX)

	RET

TEXT	runtime·badsignal2(SB),NOSPLIT,$24
	// stderr
	MOVL	$-12, 0(SP)
	MOVL	SP, BP
	CALL	*runtime·_GetStdHandle(SB)
	MOVL	BP, SP

	MOVL	AX, 0(SP)	// handle
	MOVL	$runtime·badsignalmsg(SB), DX // pointer
	MOVL	DX, 4(SP)
	MOVL	runtime·badsignallen(SB), DX // count
	MOVL	DX, 8(SP)
	LEAL	20(SP), DX  // written count
	MOVL	$0, 0(DX)
	MOVL	DX, 12(SP)
	MOVL	$0, 16(SP) // overlapped
	CALL	*runtime·_WriteFile(SB)
	MOVL	BP, SI
	RET

// faster get/set last error
TEXT runtime·getlasterror(SB),NOSPLIT,$0
	MOVL	0x34(FS), AX
	MOVL	AX, ret+0(FP)
	RET

// Called by Windows as a Vectored Exception Handler (VEH).
// First argument is pointer to struct containing
// exception record and context pointers.
// Handler function is stored in AX.
// Return 0 for 'not handled', -1 for handled.
TEXT sigtramp<>(SB),NOSPLIT,$0-0
	MOVL	ptrs+0(FP), CX
	SUBL	$40, SP

	// save callee-saved registers
	MOVL	BX, 28(SP)
	MOVL	BP, 16(SP)
	MOVL	SI, 20(SP)
	MOVL	DI, 24(SP)

	MOVL	AX, SI	// save handler address

	// find g
	get_tls(DX)
	CMPL	DX, $0
	JNE	3(PC)
	MOVL	$0, AX // continue
	JMP	done
	MOVL	g(DX), DX
	CMPL	DX, $0
	JNE	2(PC)
	CALL	runtime·badsignal2(SB)

	// save g in case of stack switch
	MOVL	DX, 32(SP)	// g
	MOVL	SP, 36(SP)

	// do we need to switch to the g0 stack?
	MOVL	g_m(DX), BX
	MOVL	m_g0(BX), BX
	CMPL	DX, BX
	JEQ	g0

	// switch to the g0 stack
	get_tls(BP)
	MOVL	BX, g(BP)
	MOVL	(g_sched+gobuf_sp)(BX), DI
	// make room for sighandler arguments
	// and re-save old SP for restoring later.
	// (note that the 36(DI) here must match the 36(SP) above.)
	SUBL	$40, DI
	MOVL	SP, 36(DI)
	MOVL	DI, SP

g0:
	MOVL	0(CX), BX // ExceptionRecord*
	MOVL	4(CX), CX // Context*
	MOVL	BX, 0(SP)
	MOVL	CX, 4(SP)
	MOVL	DX, 8(SP)
	CALL	SI	// call handler
	// AX is set to report result back to Windows
	MOVL	12(SP), AX

	// switch back to original stack and g
	// no-op if we never left.
	MOVL	36(SP), SP
	MOVL	32(SP), DX	// note: different SP
	get_tls(BP)
	MOVL	DX, g(BP)

done:
	// restore callee-saved registers
	MOVL	24(SP), DI
	MOVL	20(SP), SI
	MOVL	16(SP), BP
	MOVL	28(SP), BX

	ADDL	$40, SP
	// RET 4 (return and pop 4 bytes parameters)
	BYTE $0xC2; WORD $4
	RET // unreached; make assembler happy

TEXT runtime·exceptiontramp<ABIInternal>(SB),NOSPLIT,$0
	MOVL	$runtime·exceptionhandler(SB), AX
	JMP	sigtramp<>(SB)

TEXT runtime·firstcontinuetramp<ABIInternal>(SB),NOSPLIT,$0-0
	// is never called
	INT	$3

TEXT runtime·lastcontinuetramp<ABIInternal>(SB),NOSPLIT,$0-0
	MOVL	$runtime·lastcontinuehandler(SB), AX
	JMP	sigtramp<>(SB)

GLOBL runtime·cbctxts(SB), NOPTR, $4

TEXT runtime·callbackasm1<ABIInternal>(SB),NOSPLIT,$0
  	MOVL	0(SP), AX	// will use to find our callback context

	// remove return address from stack, we are not returning to callbackasm, but to its caller.
	ADDL	$4, SP

	// address to callback parameters into CX
	LEAL	4(SP), CX

	// save registers as required for windows callback
	PUSHL	DI
	PUSHL	SI
	PUSHL	BP
	PUSHL	BX

	// Go ABI requires DF flag to be cleared.
	CLD

	// determine index into runtime·cbs table
	SUBL	$runtime·callbackasm<ABIInternal>(SB), AX
	MOVL	$0, DX
	MOVL	$5, BX	// divide by 5 because each call instruction in runtime·callbacks is 5 bytes long
	DIVL	BX
	SUBL	$1, AX	// subtract 1 because return PC is to the next slot

	// Create a struct callbackArgs on our stack.
	SUBL	$(12+callbackArgs__size), SP
	MOVL	AX, (12+callbackArgs_index)(SP)		// callback index
	MOVL	CX, (12+callbackArgs_args)(SP)		// address of args vector
	MOVL	$0, (12+callbackArgs_result)(SP)	// result
	LEAL	12(SP), AX	// AX = &callbackArgs{...}

	// Call cgocallback, which will call callbackWrap(frame).
	MOVL	$0, 8(SP)	// context
	MOVL	AX, 4(SP)	// frame (address of callbackArgs)
	LEAL	·callbackWrap(SB), AX
	MOVL	AX, 0(SP)	// PC of function to call
	CALL	runtime·cgocallback(SB)

	// Get callback result.
	MOVL	(12+callbackArgs_result)(SP), AX
	// Get popRet.
	MOVL	(12+callbackArgs_retPop)(SP), CX	// Can't use a callee-save register
	ADDL	$(12+callbackArgs__size), SP

	// restore registers as required for windows callback
	POPL	BX
	POPL	BP
	POPL	SI
	POPL	DI

	// remove callback parameters before return (as per Windows spec)
	POPL	DX
	ADDL	CX, SP
	PUSHL	DX

	CLD

	RET

// void tstart(M *newm);
TEXT tstart<>(SB),NOSPLIT,$0
	MOVL	newm+0(FP), CX		// m
	MOVL	m_g0(CX), DX		// g

	// Layout new m scheduler stack on os stack.
	MOVL	SP, AX
	MOVL	AX, (g_stack+stack_hi)(DX)
	SUBL	$(64*1024), AX		// initial stack size (adjusted later)
	MOVL	AX, (g_stack+stack_lo)(DX)
	ADDL	$const__StackGuard, AX
	MOVL	AX, g_stackguard0(DX)
	MOVL	AX, g_stackguard1(DX)

	// Set up tls.
	LEAL	m_tls(CX), SI
	MOVL	SI, 0x14(FS)
	MOVL	CX, g_m(DX)
	MOVL	DX, g(SI)

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

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

	RET

// uint32 tstart_stdcall(M *newm);
TEXT runtime·tstart_stdcall<ABIInternal>(SB),NOSPLIT,$0
	MOVL	newm+0(FP), BX

	PUSHL	BX
	CALL	tstart<>(SB)
	POPL	BX

	// Adjust stack for stdcall to return properly.
	MOVL	(SP), AX		// save return address
	ADDL	$4, SP			// remove single parameter
	MOVL	AX, (SP)		// restore return address

	XORL	AX, AX			// return 0 == success

	RET

// setldt(int entry, int address, int limit)
TEXT runtime·setldt(SB),NOSPLIT,$0
	MOVL	base+4(FP), CX
	MOVL	CX, 0x14(FS)
	RET

// Runs on OS stack.
// duration (in -100ns units) is in dt+0(FP).
// g may be nil.
TEXT runtime·usleep2(SB),NOSPLIT,$20-4
	MOVL	dt+0(FP), BX
	MOVL	$-1, hi-4(SP)
	MOVL	BX, lo-8(SP)
	LEAL	lo-8(SP), BX
	MOVL	BX, ptime-12(SP)
	MOVL	$0, alertable-16(SP)
	MOVL	$-1, handle-20(SP)
	MOVL	SP, BP
	MOVL	runtime·_NtWaitForSingleObject(SB), AX
	CALL	AX
	MOVL	BP, SP
	RET

// Runs on OS stack.
// duration (in -100ns units) is in dt+0(FP).
// g is valid.
TEXT runtime·usleep2HighRes(SB),NOSPLIT,$36-4
	MOVL	dt+0(FP), BX
	MOVL	$-1, hi-4(SP)
	MOVL	BX, lo-8(SP)

	get_tls(CX)
	MOVL	g(CX), CX
	MOVL	g_m(CX), CX
	MOVL	(m_mOS+mOS_highResTimer)(CX), CX
	MOVL	CX, saved_timer-12(SP)

	MOVL	$0, fResume-16(SP)
	MOVL	$0, lpArgToCompletionRoutine-20(SP)
	MOVL	$0, pfnCompletionRoutine-24(SP)
	MOVL	$0, lPeriod-28(SP)
	LEAL	lo-8(SP), BX
	MOVL	BX, lpDueTime-32(SP)
	MOVL	CX, hTimer-36(SP)
	MOVL	SP, BP
	MOVL	runtime·_SetWaitableTimer(SB), AX
	CALL	AX
	MOVL	BP, SP

	MOVL	$0, ptime-28(SP)
	MOVL	$0, alertable-32(SP)
	MOVL	saved_timer-12(SP), CX
	MOVL	CX, handle-36(SP)
	MOVL	SP, BP
	MOVL	runtime·_NtWaitForSingleObject(SB), AX
	CALL	AX
	MOVL	BP, SP

	RET

// Runs on OS stack.
TEXT runtime·switchtothread(SB),NOSPLIT,$0
	MOVL	SP, BP
	MOVL	runtime·_SwitchToThread(SB), AX
	CALL	AX
	MOVL	BP, SP
	RET

// See https://wrkhpi.wordpress.com/2007/08/09/getting-os-information-the-kuser_shared_data-structure/
// Archived copy at:
// http://web.archive.org/web/20210411000829/https://wrkhpi.wordpress.com/2007/08/09/getting-os-information-the-kuser_shared_data-structure/
// Must read hi1, then lo, then hi2. The snapshot is valid if hi1 == hi2.
#define _INTERRUPT_TIME 0x7ffe0008
#define _SYSTEM_TIME 0x7ffe0014
#define time_lo 0
#define time_hi1 4
#define time_hi2 8

TEXT runtime·nanotime1(SB),NOSPLIT,$0-8
	CMPB	runtime·useQPCTime(SB), $0
	JNE	useQPC
loop:
	MOVL	(_INTERRUPT_TIME+time_hi1), AX
	MOVL	(_INTERRUPT_TIME+time_lo), CX
	MOVL	(_INTERRUPT_TIME+time_hi2), DI
	CMPL	AX, DI
	JNE	loop

	// wintime = DI:CX, multiply by 100
	MOVL	$100, AX
	MULL	CX
	IMULL	$100, DI
	ADDL	DI, DX
	// wintime*100 = DX:AX
	MOVL	AX, ret_lo+0(FP)
	MOVL	DX, ret_hi+4(FP)
	RET
useQPC:
	JMP	runtime·nanotimeQPC(SB)
	RET

TEXT time·now(SB),NOSPLIT,$0-20
	CMPB	runtime·useQPCTime(SB), $0
	JNE	useQPC
loop:
	MOVL	(_INTERRUPT_TIME+time_hi1), AX
	MOVL	(_INTERRUPT_TIME+time_lo), CX
	MOVL	(_INTERRUPT_TIME+time_hi2), DI
	CMPL	AX, DI
	JNE	loop

	// w = DI:CX
	// multiply by 100
	MOVL	$100, AX
	MULL	CX
	IMULL	$100, DI
	ADDL	DI, DX
	// w*100 = DX:AX
	MOVL	AX, mono+12(FP)
	MOVL	DX, mono+16(FP)

wall:
	MOVL	(_SYSTEM_TIME+time_hi1), CX
	MOVL	(_SYSTEM_TIME+time_lo), AX
	MOVL	(_SYSTEM_TIME+time_hi2), DX
	CMPL	CX, DX
	JNE	wall

	// w = DX:AX
	// convert to Unix epoch (but still 100ns units)
	#define delta 116444736000000000
	SUBL	$(delta & 0xFFFFFFFF), AX
	SBBL $(delta >> 32), DX

	// nano/100 = DX:AX
	// split into two decimal halves by div 1e9.
	// (decimal point is two spots over from correct place,
	// but we avoid overflow in the high word.)
	MOVL	$1000000000, CX
	DIVL	CX
	MOVL	AX, DI
	MOVL	DX, SI

	// DI = nano/100/1e9 = nano/1e11 = sec/100, DX = SI = nano/100%1e9
	// split DX into seconds and nanoseconds by div 1e7 magic multiply.
	MOVL	DX, AX
	MOVL	$1801439851, CX
	MULL	CX
	SHRL	$22, DX
	MOVL	DX, BX
	IMULL	$10000000, DX
	MOVL	SI, CX
	SUBL	DX, CX

	// DI = sec/100 (still)
	// BX = (nano/100%1e9)/1e7 = (nano/1e9)%100 = sec%100
	// CX = (nano/100%1e9)%1e7 = (nano%1e9)/100 = nsec/100
	// store nsec for return
	IMULL	$100, CX
	MOVL	CX, nsec+8(FP)

	// DI = sec/100 (still)
	// BX = sec%100
	// construct DX:AX = 64-bit sec and store for return
	MOVL	$0, DX
	MOVL	$100, AX
	MULL	DI
	ADDL	BX, AX
	ADCL	$0, DX
	MOVL	AX, sec+0(FP)
	MOVL	DX, sec+4(FP)
	RET
useQPC:
	JMP	runtime·nowQPC(SB)
	RET