/*
 * Based on:
 *
 * Minimal BPF JIT image disassembler
 *
 * Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
 * debugging or verification purposes.
 *
 * Copyright 2013 Daniel Borkmann <daniel@iogearbox.net>
 * Licensed under the GNU General Public License, version 2.0 (GPLv2)
 */

#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <unistd.h>
#include <string.h>
#include <bfd.h>
#include <dis-asm.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <limits.h>

#include "json_writer.h"
#include "main.h"

static void get_exec_path(char *tpath, size_t size)
{
        ssize_t len;
        char *path;

        snprintf(tpath, size, "/proc/%d/exe", (int) getpid());
        tpath[size - 1] = 0;

        path = strdup(tpath);
        assert(path);

        len = readlink(path, tpath, size - 1);
        assert(len > 0);
        tpath[len] = 0;

        free(path);
}

static int oper_count;
static int fprintf_json(void *out, const char *fmt, ...)
{
        va_list ap;
        char *s;

        va_start(ap, fmt);
        if (!oper_count) {
                int i;

                s = va_arg(ap, char *);

                /* Strip trailing spaces */
                i = strlen(s) - 1;
                while (s[i] == ' ')
                        s[i--] = '\0';

                jsonw_string_field(json_wtr, "operation", s);
                jsonw_name(json_wtr, "operands");
                jsonw_start_array(json_wtr);
                oper_count++;
        } else if (!strcmp(fmt, ",")) {
                   /* Skip */
        } else {
                s = va_arg(ap, char *);
                jsonw_string(json_wtr, s);
                oper_count++;
        }
        va_end(ap);
        return 0;
}

void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
                       const char *arch)
{
        disassembler_ftype disassemble;
        struct disassemble_info info;
        int count, i, pc = 0;
        char tpath[PATH_MAX];
        bfd *bfdf;

        if (!len)
                return;

        memset(tpath, 0, sizeof(tpath));
        get_exec_path(tpath, sizeof(tpath));

        bfdf = bfd_openr(tpath, NULL);
        assert(bfdf);
        assert(bfd_check_format(bfdf, bfd_object));

        if (json_output)
                init_disassemble_info(&info, stdout,
                                      (fprintf_ftype) fprintf_json);
        else
                init_disassemble_info(&info, stdout,
                                      (fprintf_ftype) fprintf);

        /* Update architecture info for offload. */
        if (arch) {
                const bfd_arch_info_type *inf = bfd_scan_arch(arch);

                if (inf) {
                        bfdf->arch_info = inf;
                } else {
                        p_err("No libfd support for %s", arch);
                        return;
                }
        }

        info.arch = bfd_get_arch(bfdf);
        info.mach = bfd_get_mach(bfdf);
        info.buffer = image;
        info.buffer_length = len;

        disassemble_init_for_target(&info);

#ifdef DISASM_FOUR_ARGS_SIGNATURE
        disassemble = disassembler(info.arch,
                                   bfd_big_endian(bfdf),
                                   info.mach,
                                   bfdf);
#else
        disassemble = disassembler(bfdf);
#endif
        assert(disassemble);

        if (json_output)
                jsonw_start_array(json_wtr);
        do {
                if (json_output) {
                        jsonw_start_object(json_wtr);
                        oper_count = 0;
                        jsonw_name(json_wtr, "pc");
                        jsonw_printf(json_wtr, "\"0x%x\"", pc);
                } else {
                        printf("%4x:\t", pc);
                }

                count = disassemble(pc, &info);
                if (json_output) {
                        /* Operand array, was started in fprintf_json. Before
                         * that, make sure we have a _null_ value if no operand
                         * other than operation code was present.
                         */
                        if (oper_count == 1)
                                jsonw_null(json_wtr);
                        jsonw_end_array(json_wtr);
                }

                if (opcodes) {
                        if (json_output) {
                                jsonw_name(json_wtr, "opcodes");
                                jsonw_start_array(json_wtr);
                                for (i = 0; i < count; ++i)
                                        jsonw_printf(json_wtr, "\"0x%02hhx\"",
                                                     (uint8_t)image[pc + i]);
                                jsonw_end_array(json_wtr);
                        } else {
                                printf("\n\t");
                                for (i = 0; i < count; ++i)
                                        printf("%02x ",
                                               (uint8_t)image[pc + i]);
                        }
                }
                if (json_output)
                        jsonw_end_object(json_wtr);
                else
                        printf("\n");

                pc += count;
        } while (count > 0 && pc < len);
        if (json_output)
                jsonw_end_array(json_wtr);

        bfd_close(bfdf);
}