nativelibc/process/fork.c

/*	A part of the Native C Library for Windows NT
	Copyright 2007-2015 PC GO Ld.
	Copyright 2016-2026 Rivoreo

	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 <sys/types.h>
#include <stdint.h>
#include <windows.h>
#include <nt.h>
#include <errno.h>
#include <unistd.h>
#include <process.h>

static int is_child = 0;

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

	CONTEXT context = { .ContextFlags = CONTEXT_FULL | CONTEXT_FLOATING_POINT };
	long int status = NtGetContextThread((void *)-2, &context);
	if(status < 0) {
		__set_errno_from_ntstatus(status);
		return -1;
	}

	void *ph;
	OBJECT_ATTRIBUTES empty_obj_attr = { .Length = sizeof(OBJECT_ATTRIBUTES) };
	status = NtCreateProcess(&ph, PROCESS_ALL_ACCESS, &empty_obj_attr, (void *)-1, 1, NULL, NULL, NULL);
	if(status < 0) {
		__set_errno_from_ntstatus(status);
		return -1;
	}

	MEMORY_BASIC_INFORMATION mbi;

#ifdef __i386__
	context.Eip = (uint32_t)fork + 12;
	status = NtQueryVirtualMemory((void *)-1, (void *)context.Esp, MemoryBasicInformation, &mbi, sizeof mbi, NULL);
	if(status < 0) {
		__set_errno_from_ntstatus(status);
		NtClose(ph);
		return -1;
	}
#else
#error "Architecture not supported"
#endif

	void *th;
	INITIAL_TEB stack =  { 0, 0, (char *)mbi.BaseAddress + mbi.RegionSize, mbi.BaseAddress, mbi.AllocationBase };
	CLIENT_ID cid;
	status = NtCreateThread(&th, THREAD_ALL_ACCESS, &empty_obj_attr, ph, &cid, &context, &stack, 1);
	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;

	int value = 1;
	status = NtWriteVirtualMemory(ph, &is_child, &value, sizeof value, NULL);
	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;
}