libopcodes command-line invocation

loctool.c

/*

## loctool: (libopcode tool) programmatically call the same disassembler objdump uses
* depends: libiberty, libbfd, libopcodes all from binutils

## setup
* get [binutils 2.30](https://ftp.gnu.org/gnu/binutils/binutils-2.30.tar.gz) and decompress.
* enter the libiberty directory, `./configure && make` then `cp libiberty.a /usr/local/lib`
* enter the bfd directory, edit configure and set all_targets=true then `./configure && make && make install`
* enter the opcodes directory, edit configure and set all_targets=true then `./configure && make && make install`

## compile/link
* `gcc loctool.c -o loctool -lopcodes -lbfd -liberty -lz`

*/

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

#define PACKAGE "bfd"
#define PACKAGE_VERSION "2.30"
#include <bfd.h> // for bfd_arch_arm, etc. ~/downloads/binutils-2.30/bfd/bfd.h
#include <dis-asm.h> // for struct disassemble_info, etc. ~/downloads/binutils-2.30/include/dis-asm.h

int cb_fprintf(void *stream, const char *fmt, ...)
{
	va_list args;
	va_start(args, fmt);

	//printf("cb_fprintf(stream, \"%s\")\n", fmt);

	char *built_str = (char *)stream;
	char buf[1024];
	int rc = vsnprintf(buf, sizeof(buf)-1, fmt, args);
	va_end(args);
	strcat((char *)built_str, buf);
	return rc;
}

int disasm_libopcodes(uint8_t *data, int len, uint64_t addr, char *result)
{
	disassemble_info dinfo = {0};

	/* create disassemble_info */
	init_disassemble_info(&dinfo, NULL, NULL);
	dinfo.flavour = bfd_target_unknown_flavour;
	dinfo.arch = bfd_arch_mips;
	dinfo.mach = bfd_mach_mipsisa32r6;
	dinfo.endian = BFD_ENDIAN_BIG;
	disassemble_init_for_target(&dinfo); // reads dinfo.arch and populate extra stuff

	/* use the stream pointer as our private data
		(the buffer that fprintf() should append to) */
	dinfo.stream = (void *)result;

	/* create disassembler */
	disassembler_ftype disasm = disassembler(bfd_arch_mips, TRUE, bfd_mach_mipsisa32r6, NULL);
	if(!disasm) {
		printf("ERROR: disassembler() returned no function\n");
		return -1;
	}

	/* call disassembler
		will use callbacks in dinfo (like .read_memory_func, .print_addr_func, etc.)
		and the defaults are fine for this use case, see the defaults in a debugger
		or look at especially buffer_read_memory() in dis-buf.c for details */
	dinfo.fprintf_func = cb_fprintf;
	dinfo.octets_per_byte = 1;
	dinfo.buffer_vma = addr;
	dinfo.stop_vma = addr + len;
	/* source data */
	dinfo.buffer = data;
	dinfo.buffer_length = len;

	result[0] = '\0';
	disasm((bfd_vma)addr, &dinfo);

	return 0;
}

int main(int ac, char **av)
{
	char result[1024];
	//uint8_t data[4] = {0x11, 0x22, 0x33, 0x44};
	uint8_t data[4];

	if(ac<2) {
		printf("supply instruction word\n");
		return -1;
	}

	uint32_t insword = strtoul(av[1], NULL, 16);
	data[0] = (insword >> 24) & 0xff;
	data[1] = (insword >> 16) & 0xFF;
	data[2] = (insword >> 8) & 0xFF;
	data[3] = (insword) & 0xFF;

	printf("disassembling %02X%02X%02X%02X...\n",
		data[0], data[1], data[2], data[3]);

	if(disasm_libopcodes(data, 4, 0, result)) {
		printf("ERROR: disasm_libopcodes()\n");
		return -1;
	}

	printf("%s\n", result);

	return 0;
}