jmp and call generator

jmpcallgen.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct OpCode {
	char* mne;
	char* opcode;
};

struct OpCode opcodes[] = {
	{ "jmp", "\\xeb" },
	{ "long_jmp", "\\xe9" },
	{ "je" , "\\x74" },
	{ "long_je" , "\\x0f\\x84" },
	{ "jne", "\\x75" },
	{ "long_jne" , "\\x0f\\x85" },
	{ "jle", "\\x7e" },
	{ "long_jle", "\\x0f\\x8e" },
	{ "jl" , "\\x7c" },
	{ "jb" , "\\x72" },
	{ "long_jb", "\\x0f\\x82" },
	{ "jbe", "\\x76" },
	{ "jg" , "\\x7f" },
	{ "js" , "\\x78" },
	{ "long_js", "\\x0f\\x88" },
	{ "jns", "\\x79" },
	{ "ja" , "\\x77" },
	{ "jae", "\\x73" },
	{ "jge", "\\x7d" },
	{ "call", "\\xe8" }};

int op_size = sizeof(opcodes) / sizeof(struct OpCode);

void generate(struct OpCode,char*,char*);

char*
getLong(char* op)
{
	int i;
	char* tmp = malloc(5 + strlen(op));

	sprintf(tmp,"long_%s",op);

	for(i = 0;i < op_size;i++)
		if(!strcmp(opcodes[i].mne,tmp))
			return opcodes[i].opcode;

	return NULL;
}

int
main(int argc,char* argv[])
{
	int i;

	if(argc == 4)
		for(i = 0;i < op_size;i++)
			if(!strcmp(argv[1],opcodes[i].mne))
				generate(opcodes[i],argv[2],argv[3]);

	printf("* Instruction not found. Available instructions:\n");

	for(i = 0;i < op_size;i++)
		if(strncmp(opcodes[i].mne,"long_",5) && opcodes[i].mne[0] != '*')
			printf(" - %s\n",opcodes[i].mne);

	return 0;
}

void
generate(struct OpCode code,char* address0,char* address1)
{
	int addr0,addr1;
	unsigned char addr[5];

	signed int addr2;

	if(!address0 || !address1)
		exit(1);

	sscanf(address0,"%x",&addr0);
	sscanf(address1,"%x",&addr1);

	addr2 = (signed int)(addr1 - addr0);

	memcpy(addr, &addr2, 4);

	if(address0[0] == '*')
	{
		if(strcmp(code.mne,"jmp") && strcmp(code.mne,"call"))
		{
			printf("* Error, indirect jump and call only available with jmp and call.\n");
			exit(1);
		}

		sscanf(address0 + 1,"%x",&addr0);

		memcpy(addr, &addr0, 4);

		printf("%s\\x%02x\\x%02x\\x%02x\\x%02x\n", 
				(!strcmp(code.mne,"jmp")) ? "\\xff\\x25" : "\\xff\\x15" , addr[0],addr[1],addr[2],addr[3]);

		exit(0);
	}

	if(address0[0] == '%')
	{
		printf("\\xff");

		if(!strcmp(address0, "%eax"))
			printf("\\x%02x\n", ( code.mne[0] == 'j' ? 0xe0 : 0xd0 ));
		else if(!strcmp(address0, "%ecx"))
			printf("\\x%02x\n", ( code.mne[0] == 'j' ? 0xe1 : 0xd1 ));
		else if(!strcmp(address0, "%edx"))
			printf("\\x%02x\n", ( code.mne[0] == 'j' ? 0xe2 : 0xd2 ));
		else if(!strcmp(address0, "%ebx"))
			printf("\\x%02x\n", ( code.mne[0] == 'j' ? 0xe3 : 0xd3 ));
		else if(!strcmp(address0, "%esp"))
			printf("\\x%02x\n", ( code.mne[0] == 'j' ? 0xe4 : 0xd4 ));
		else if(!strcmp(address0, "%ebp"))
			printf("\\x%02x\n", ( code.mne[0] == 'j' ? 0xe5 : 0xd5 ));
		else if(!strcmp(address0, "%esi"))
			printf("\\x%02x\n", ( code.mne[0] == 'j' ? 0xe6 : 0xd6 ));
		else if(!strcmp(address0, "%edi"))
			printf("\\x%02x\n", ( code.mne[0] == 'j' ? 0xe7 : 0xd7 ));

		exit(0);
	}

	if(!strcmp(code.mne,"call"))
	{
		printf("%s\\x%02x\\x%02x\\x%02x\\x%02x\n", code.opcode, addr[0],addr[1],addr[2],addr[3]);

		exit(0);
	}

	if(addr2 >= -99 && (addr2 <= 0xff))
		printf("%s\\x%02x\n",code.opcode, (unsigned char) addr[0]);
	else
		printf("%s\\x%02x\\x%02x\\x%02x\\x%02x\n",(getLong(code.mne) ? getLong(code.mne) : code.opcode ), addr[0],addr[1],addr[2],addr[3]);

	exit(0);
}