4 * Minimal BPF JIT image disassembler
6 * Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
7 * debugging or verification purposes.
9 * Copyright 2013 Daniel Borkmann <daniel@iogearbox.net>
10 * Licensed under the GNU General Public License, version 2.0 (GPLv2)
22 #include <sys/types.h>
26 #include "json_writer.h"
29 static void get_exec_path(char *tpath, size_t size)
34 snprintf(tpath, size, "/proc/%d/exe", (int) getpid());
40 len = readlink(path, tpath, size - 1);
47 static int oper_count;
48 static int fprintf_json(void *out, const char *fmt, ...)
57 s = va_arg(ap, char *);
59 /* Strip trailing spaces */
64 jsonw_string_field(json_wtr, "operation", s);
65 jsonw_name(json_wtr, "operands");
66 jsonw_start_array(json_wtr);
68 } else if (!strcmp(fmt, ",")) {
71 s = va_arg(ap, char *);
72 jsonw_string(json_wtr, s);
79 void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
82 disassembler_ftype disassemble;
83 struct disassemble_info info;
91 memset(tpath, 0, sizeof(tpath));
92 get_exec_path(tpath, sizeof(tpath));
94 bfdf = bfd_openr(tpath, NULL);
96 assert(bfd_check_format(bfdf, bfd_object));
99 init_disassemble_info(&info, stdout,
100 (fprintf_ftype) fprintf_json);
102 init_disassemble_info(&info, stdout,
103 (fprintf_ftype) fprintf);
105 /* Update architecture info for offload. */
107 const bfd_arch_info_type *inf = bfd_scan_arch(arch);
110 bfdf->arch_info = inf;
112 p_err("No libfd support for %s", arch);
117 info.arch = bfd_get_arch(bfdf);
118 info.mach = bfd_get_mach(bfdf);
120 info.buffer_length = len;
122 disassemble_init_for_target(&info);
124 #ifdef DISASM_FOUR_ARGS_SIGNATURE
125 disassemble = disassembler(info.arch,
126 bfd_big_endian(bfdf),
130 disassemble = disassembler(bfdf);
135 jsonw_start_array(json_wtr);
138 jsonw_start_object(json_wtr);
140 jsonw_name(json_wtr, "pc");
141 jsonw_printf(json_wtr, "\"0x%x\"", pc);
143 printf("%4x:\t", pc);
146 count = disassemble(pc, &info);
148 /* Operand array, was started in fprintf_json. Before
149 * that, make sure we have a _null_ value if no operand
150 * other than operation code was present.
153 jsonw_null(json_wtr);
154 jsonw_end_array(json_wtr);
159 jsonw_name(json_wtr, "opcodes");
160 jsonw_start_array(json_wtr);
161 for (i = 0; i < count; ++i)
162 jsonw_printf(json_wtr, "\"0x%02hhx\"",
163 (uint8_t)image[pc + i]);
164 jsonw_end_array(json_wtr);
167 for (i = 0; i < count; ++i)
169 (uint8_t)image[pc + i]);
173 jsonw_end_object(json_wtr);
178 } while (count > 0 && pc < len);
180 jsonw_end_array(json_wtr);