// 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.

// PE (Portable Executable) file writing
// http://www.microsoft.com/whdc/system/platform/firmware/PECOFF.mspx

#include <time.h>

#include "l.h"
#include "../ld/lib.h"
#include "../ld/pe.h"

// DOS stub that prints out
// "This program cannot be run in DOS mode."
static char dosstub[] =
{
	0x4d, 0x5a, 0x90, 0x00, 0x03, 0x00, 0x04, 0x00,
	0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00,
	0x8b, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x80, 0x00, 0x00, 0x00,
	0x0e, 0x1f, 0xba, 0x0e, 0x00, 0xb4, 0x09, 0xcd,
	0x21, 0xb8, 0x01, 0x4c, 0xcd, 0x21, 0x54, 0x68,
	0x69, 0x73, 0x20, 0x70, 0x72, 0x6f, 0x67, 0x72,
	0x61, 0x6d, 0x20, 0x63, 0x61, 0x6e, 0x6e, 0x6f,
	0x74, 0x20, 0x62, 0x65, 0x20, 0x72, 0x75, 0x6e,
	0x20, 0x69, 0x6e, 0x20, 0x44, 0x4f, 0x53, 0x20,
	0x6d, 0x6f, 0x64, 0x65, 0x2e, 0x0d, 0x0d, 0x0a,
	0x24, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};

int32 PESECTHEADR;
int32 PEFILEHEADR;

static int pe64;
static int nsect;
static int nextsectoff;
static int nextfileoff;

static IMAGE_FILE_HEADER fh;
static IMAGE_OPTIONAL_HEADER oh;
static IMAGE_SECTION_HEADER sh[16];

static IMAGE_SECTION_HEADER*
addpesection(char *name, int sectsize, int filesize, Segment *s)
{
	IMAGE_SECTION_HEADER *h;

	if(nsect == 16) {
		diag("too many sections");
		errorexit();
	}
	h = &sh[nsect++];
	strncpy((char*)h->Name, name, sizeof(h->Name));
	h->VirtualSize = sectsize;
	h->VirtualAddress = nextsectoff;
	nextsectoff = rnd(nextsectoff+sectsize, PESECTALIGN);
	h->PointerToRawData = nextfileoff;
	if(filesize > 0) {
		h->SizeOfRawData = rnd(filesize, PEFILEALIGN);
		nextfileoff += h->SizeOfRawData;
	}
	if(s) {
		if(s->vaddr-PEBASE != h->VirtualAddress) {
			diag("%s.VirtualAddress = %#llux, want %#llux", name, (vlong)h->VirtualAddress, (vlong)(s->vaddr-PEBASE));
			errorexit();
		}
		if(s->fileoff != h->PointerToRawData) {
			diag("%s.PointerToRawData = %#llux, want %#llux", name, (vlong)h->PointerToRawData, (vlong)(s->fileoff));
			errorexit();
		}
	}
	return h;
}

void
peinit(void)
{
	switch(thechar) {
	// 64-bit architectures
	case '6':
		pe64 = 1;
		break;
	// 32-bit architectures
	default:
		break;
	}

	PEFILEHEADR = rnd(sizeof(dosstub)+sizeof(fh)+sizeof(oh)+sizeof(sh), PEFILEALIGN);
	PESECTHEADR = rnd(PEFILEHEADR, PESECTALIGN);
	nextsectoff = PESECTHEADR;
	nextfileoff = PEFILEHEADR;
}

static void
pewrite(void)
{
	int i, j;

	seek(cout, 0, 0);
	ewrite(cout, dosstub, sizeof dosstub);
	strnput("PE", 4);

	for (i=0; i<sizeof(fh); i++)
		cput(((char*)&fh)[i]);
	for (i=0; i<sizeof(oh); i++)
		cput(((char*)&oh)[i]);
	for (i=0; i<nsect; i++)
		for (j=0; j<sizeof(sh[i]); j++)
			cput(((char*)&sh[i])[j]);
}

static void
strput(char *s)
{
	while(*s)
		cput(*s++);
	cput('\0');
}

static void
addimports(vlong fileoff)
{
	IMAGE_IMPORT_DESCRIPTOR ds[2], *d;
	char *dllname = "kernel32.dll";
	struct {
		char *name;
		uint32 thunk;
	} *f, fs[] = {
		{ "GetProcAddress", 0 },
		{ "LoadLibraryExA", 0 },
		{ 0, 0 }
	};

	uint32 size = 0;
	memset(ds, 0, sizeof(ds));
	size += sizeof(ds);
	ds[0].Name = size;
	size += strlen(dllname) + 1;
	for(f=fs; f->name; f++) {
		f->thunk = size;
		size += sizeof(uint16) + strlen(f->name) + 1;
	}
	ds[0].FirstThunk = size;
	for(f=fs; f->name; f++)
		size += sizeof(fs[0].thunk);

	IMAGE_SECTION_HEADER *isect;
	isect = addpesection(".idata", size, size, 0);
	isect->Characteristics = IMAGE_SCN_CNT_INITIALIZED_DATA|
		IMAGE_SCN_MEM_READ|IMAGE_SCN_MEM_WRITE;
	
	uint32 va = isect->VirtualAddress;
	oh.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress = va;
	oh.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].Size = isect->VirtualSize;

	ds[0].Name += va;
	ds[0].FirstThunk += va;
	for(f=fs; f->name; f++)
		f->thunk += va;

	seek(cout, fileoff, 0);
	for(d=ds; ; d++) {
		lputl(d->OriginalFirstThunk);
		lputl(d->TimeDateStamp);
		lputl(d->ForwarderChain);
		lputl(d->Name);
		lputl(d->FirstThunk);
		if(!d->Name) 
			break;
	}
	strput(dllname);
	for(f=fs; f->name; f++) {
		wputl(0);
		strput(f->name);
	}
	for(f=fs; f->name; f++)
		lputl(f->thunk);
	strnput("", isect->SizeOfRawData - size);
	cflush();
}

void
asmbpe(void)
{
	IMAGE_SECTION_HEADER *t, *d;

	switch(thechar) {
	default:
		diag("unknown PE architecture");
		errorexit();
	case '6':
		fh.Machine = IMAGE_FILE_MACHINE_AMD64;
		break;
	case '8':
		fh.Machine = IMAGE_FILE_MACHINE_I386;
		break;
	}

	t = addpesection(".text", segtext.len, segtext.len, &segtext);
	t->Characteristics = IMAGE_SCN_CNT_CODE|
		IMAGE_SCN_CNT_INITIALIZED_DATA|
		IMAGE_SCN_MEM_EXECUTE|IMAGE_SCN_MEM_READ;

	d = addpesection(".data", segdata.len, segdata.filelen, &segdata);
	d->Characteristics = IMAGE_SCN_CNT_INITIALIZED_DATA|
		IMAGE_SCN_MEM_READ|IMAGE_SCN_MEM_WRITE;

	addimports(nextfileoff);

	fh.NumberOfSections = nsect;
	fh.TimeDateStamp = time(0);
	fh.SizeOfOptionalHeader = sizeof(oh);
	fh.Characteristics = IMAGE_FILE_RELOCS_STRIPPED|
		IMAGE_FILE_EXECUTABLE_IMAGE|IMAGE_FILE_DEBUG_STRIPPED;
	if(thechar == '8')
		fh.Characteristics |= IMAGE_FILE_32BIT_MACHINE;

	oh.Magic = 0x10b;	// PE32
	oh.MajorLinkerVersion = 1;
	oh.MinorLinkerVersion = 0;
	oh.SizeOfCode = t->SizeOfRawData;
	oh.SizeOfInitializedData = d->SizeOfRawData;
	oh.SizeOfUninitializedData = 0;
	oh.AddressOfEntryPoint = entryvalue()-PEBASE;
	oh.BaseOfCode = t->VirtualAddress;
	oh.BaseOfData = d->VirtualAddress;

	oh.ImageBase = PEBASE;
	oh.SectionAlignment = PESECTALIGN;
	oh.FileAlignment = PEFILEALIGN;
	oh.MajorOperatingSystemVersion = 4;
	oh.MinorOperatingSystemVersion = 0;
	oh.MajorImageVersion = 1;
	oh.MinorImageVersion = 0;
	oh.MajorSubsystemVersion = 4;
	oh.MinorSubsystemVersion = 0;
	oh.SizeOfImage = nextsectoff;
	oh.SizeOfHeaders = PEFILEHEADR;
	oh.Subsystem = 3;	// WINDOWS_CUI
	oh.SizeOfStackReserve = 0x00200000;
	oh.SizeOfStackCommit = 0x00001000;
	oh.SizeOfHeapReserve = 0x00100000;
	oh.SizeOfHeapCommit = 0x00001000;
	oh.NumberOfRvaAndSizes = 16;

	pewrite();
}