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
)
81 disassembler_ftype disassemble
;
82 struct disassemble_info info
;
90 memset(tpath
, 0, sizeof(tpath
));
91 get_exec_path(tpath
, sizeof(tpath
));
93 bfdf
= bfd_openr(tpath
, NULL
);
95 assert(bfd_check_format(bfdf
, bfd_object
));
98 init_disassemble_info(&info
, stdout
,
99 (fprintf_ftype
) fprintf_json
);
101 init_disassemble_info(&info
, stdout
,
102 (fprintf_ftype
) fprintf
);
103 info
.arch
= bfd_get_arch(bfdf
);
104 info
.mach
= bfd_get_mach(bfdf
);
106 info
.buffer_length
= len
;
108 disassemble_init_for_target(&info
);
110 disassemble
= disassembler(bfdf
);
114 jsonw_start_array(json_wtr
);
117 jsonw_start_object(json_wtr
);
119 jsonw_name(json_wtr
, "pc");
120 jsonw_printf(json_wtr
, "\"0x%x\"", pc
);
122 printf("%4x:\t", pc
);
125 count
= disassemble(pc
, &info
);
127 /* Operand array, was started in fprintf_json. Before
128 * that, make sure we have a _null_ value if no operand
129 * other than operation code was present.
132 jsonw_null(json_wtr
);
133 jsonw_end_array(json_wtr
);
138 jsonw_name(json_wtr
, "opcodes");
139 jsonw_start_array(json_wtr
);
140 for (i
= 0; i
< count
; ++i
)
141 jsonw_printf(json_wtr
, "\"0x%02hhx\"",
142 (uint8_t)image
[pc
+ i
]);
143 jsonw_end_array(json_wtr
);
146 for (i
= 0; i
< count
; ++i
)
148 (uint8_t)image
[pc
+ i
]);
152 jsonw_end_object(json_wtr
);
157 } while (count
> 0 && pc
< len
);
159 jsonw_end_array(json_wtr
);