nativelibc/process/fork.c

/*	A part of the Native C Library for Windows NT
	Copyright 2007-2015 PC GO Ld.

	This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

	This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
*/

#include <windows.h>
#include <nt.h>
#include <errno.h>
#include <unistd.h>
#include <process.h>

//#include <stdio.h>

static int is_child = 0;

pid_t fork() {
	if(is_child) {
		is_child = 0;
		return 0;
	}

	void *ph, *th;
	OBJECT_ATTRIBUTES object_attrib = { sizeof(OBJECT_ATTRIBUTES), NULL, NULL, 0, NULL, NULL };
	long int status = NtCreateProcess(&ph, PROCESS_ALL_ACCESS, &object_attrib, (void *)-1, 1, NULL, NULL, NULL);
	//printf("nativelibc debug: fork: status = 0x%lx\n", status);
	if(status < 0) {
		__set_errno_from_ntstatus(status);
		return -1;
	}
	CONTEXT context = { .ContextFlags = CONTEXT_FULL | CONTEXT_FLOATING_POINT };
	status = NtGetContextThread((void *)-2, &context);
	//printf("nativelibc debug: fork: status = 0x%lx\n", status);
	if(status < 0) {
		NtClose(ph);
		__set_errno_from_ntstatus(status);
		return -1;
	}

#ifdef __i386__
	__asm__("	movl	%%gs, %0\n" : "=r"(context.SegGs));
	__asm__("	movl	%%fs, %0\n" : "=r"(context.SegFs));
	__asm__("	movl	%%es, %0\n" : "=r"(context.SegEs));
	__asm__("	movl	%%ds, %0\n" : "=r"(context.SegDs));
	__asm__("	movl	%%edi, %0\n" : "=r"(context.Edi));
	__asm__("	movl	%%esi, %0\n" : "=r"(context.Esi));
	__asm__("	movl	%%ebx, %0\n" : "=r"(context.Ebx));
	__asm__("	movl	%%edx, %0\n" : "=r"(context.Edx));
	__asm__("	movl	%%ecx, %0\n" : "=r"(context.Ecx));
	__asm__("	movl	%%eax, %0\n" : "=r"(context.Eax));
	__asm__("	movl	%%ebp, %0\n" : "=r"(context.Ebp));
	__asm__("	movl	%%cs, %0\n" : "=r"(context.SegCs));
	__asm__("	movl	%%esp, %0\n" : "=r"(context.Esp));
	__asm__("	movl	%%ss, %0\n" : "=r"(context.SegSs));
#if 0
	printf("nativelibc debug:\n"
		"Dr0=%lx, Dr1=%lx, Dr2=%lx, Dr3=%lx, Dr6=%lx, Dr7=%lx,\n"
		"SegGs = %lx, SegFs = %lx, SegEs = %lx, SegDs = %lx,\n"
		"Edi=%lx, Esi=%lx, Ebx=%lx, Edx=%lx, Ecx=%lx, Eax=%lx, Ebp=%lx, Eip=%lx,\n"
		"SegCs = %lx, EFlags = %lx, Esp=%lx, SegSs = %lx\n",
		context.Dr0,
		context.Dr1,
		context.Dr2,
		context.Dr3,
		context.Dr6,
		context.Dr7,
		context.SegGs,
		context.SegFs,
		context.SegEs,
		context.SegDs,
		context.Edi,
		context.Esi,
		context.Ebx,
		context.Edx,
		context.Ecx,
		context.Eax,
		context.Ebp,
		context.Eip,
		context.SegCs,
		context.EFlags,
		context.Esp,
		context.SegSs);
#endif
	context.Eip = (unsigned long int)fork + 31;
	//printf("fork = %p, context.Eip = 0x%lx\n", fork, context.Eip);
	MEMORY_BASIC_INFORMATION mbi;
	status = NtQueryVirtualMemory((void *)-1, (void *)context.Esp, MemoryBasicInformation, &mbi, sizeof mbi, NULL);
	//printf("nativelibc debug: fork: status = 0x%lx\n", status);
	if(status < 0) {
		NtClose(ph);
		__set_errno_from_ntstatus(status);
		return -1;
	}
#else
#error "Not supported arch"
#endif
	INITIAL_TEB stack =  { 0, 0, (char *)mbi.BaseAddress + mbi.RegionSize, mbi.BaseAddress, mbi.AllocationBase };
	CLIENT_ID cid;
	status = NtCreateThread(&th, THREAD_ALL_ACCESS, &object_attrib, ph, &cid, &context, &stack, 1);
	//printf("nativelibc debug: fork: status = 0x%lx\n", status);
	if(status < 0) {
		NtClose(ph);
		__set_errno_from_ntstatus(status);
		return -1;
	}

	THREAD_BASIC_INFORMATION tbi;
	status = NtQueryInformationThread((void *)-2, ThreadBasicInformation, &tbi, sizeof tbi, NULL);
	//printf("nativelibc debug: fork: status = 0x%lx\n", status);
	if(status < 0) goto failed;

	NT_TIB *tib = &tbi.TebBaseAddress->Tib;
	status = NtQueryInformationThread(th, ThreadBasicInformation, &tbi, sizeof tbi, NULL);
	//printf("nativelibc debug: fork: status = 0x%lx\n", status);
	if(status < 0) goto failed;

	status = NtWriteVirtualMemory(ph, tbi.TebBaseAddress, &tib->ExceptionList, sizeof tib->ExceptionList, NULL);
	//printf("nativelibc debug: fork: status = 0x%lx\n", status);
	if(status < 0) goto failed;

	status = NtResumeThread(th, NULL);
	//printf("nativelibc debug: fork: status = 0x%lx\n", status);
	NtClose(th);
	if(status < 0) {
		NtClose(ph);
		__set_errno_from_ntstatus(status);
		return -1;
	}

	__child_process_table_add(cid.UniqueProcess, ph);
	return cid.UniqueProcess;

failed:
	NtClose(ph);
	NtClose(th);
	__set_errno_from_ntstatus(status);
	return -1;
}