Commit f05e2c32 authored by Quentin Monnet's avatar Quentin Monnet Committed by David S. Miller
Browse files

tools: bpftool: add JSON output for `bpftool prog dump xlated *` command 



Add a new printing function to dump translated eBPF instructions as
JSON. As for plain output, opcodes are printed only on request (when
`opcodes` is provided on the command line).

The disassembled output is generated by the same code that is used by
the kernel verifier.

Example output:

    $ bpftool --json --pretty prog dump xlated id 1
    [{
            "disasm": "(bf) r6 = r1"
        },{
            "disasm": "(61) r7 = *(u32 *)(r6 +16)"
        },{
            "disasm": "(95) exit"
        }
    ]

    $ bpftool --json --pretty prog dump xlated id 1 opcodes
    [{
            "disasm": "(bf) r6 = r1",
            "opcodes": {
                "code": "0xbf",
                "src_reg": "0x1",
                "dst_reg": "0x6",
                "off": ["0x00","0x00"
                ],
                "imm": ["0x00","0x00","0x00","0x00"
                ]
            }
        },{
            "disasm": "(61) r7 = *(u32 *)(r6 +16)",
            "opcodes": {
                "code": "0x61",
                "src_reg": "0x6",
                "dst_reg": "0x7",
                "off": ["0x10","0x00"
                ],
                "imm": ["0x00","0x00","0x00","0x00"
                ]
            }
        },{
            "disasm": "(95) exit",
            "opcodes": {
                "code": "0x95",
                "src_reg": "0x0",
                "dst_reg": "0x0",
                "off": ["0x00","0x00"
                ],
                "imm": ["0x00","0x00","0x00","0x00"
                ]
            }
        }
    ]

Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 107f0412

tools/bpf/bpftool/common.c

+10 −0
Original line number Diff line number Diff line
@@ -214,3 +214,13 @@ char *get_fdinfo(int fd, const char *key) 
	fclose(fdi);

	return NULL;

}



void print_hex_data_json(uint8_t *data, size_t len)

{

	unsigned int i;



	jsonw_start_array(json_wtr);

	for (i = 0; i < len; i++)

		jsonw_printf(json_wtr, "\"0x%02hhx\"", data[i]);

	jsonw_end_array(json_wtr);

}

tools/bpf/bpftool/json_writer.c

+8 −0
Original line number Diff line number Diff line
@@ -156,6 +156,14 @@ void jsonw_name(json_writer_t *self, const char *name) 
		putc(' ', self->out);

}



void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap)

{

	jsonw_eor(self);

	putc('"', self->out);

	vfprintf(self->out, fmt, ap);

	putc('"', self->out);

}



void jsonw_printf(json_writer_t *self, const char *fmt, ...)

{

	va_list ap;

tools/bpf/bpftool/json_writer.h

+2 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 


#include <stdbool.h>

#include <stdint.h>

#include <stdarg.h>



/* Opaque class structure */

typedef struct json_writer json_writer_t;
@@ -33,6 +34,7 @@ void jsonw_pretty(json_writer_t *self, bool on); 
void jsonw_name(json_writer_t *self, const char *name);



/* Add value  */

void jsonw_vprintf_enquote(json_writer_t *self, const char *fmt, va_list ap);

void jsonw_printf(json_writer_t *self, const char *fmt, ...);

void jsonw_string(json_writer_t *self, const char *value);

void jsonw_bool(json_writer_t *self, bool value);

tools/bpf/bpftool/main.h

+1 −0
Original line number Diff line number Diff line
@@ -95,5 +95,6 @@ int do_map(int argc, char **arg); 
int prog_parse_fd(int *argc, char ***argv);



void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes);

void print_hex_data_json(uint8_t *data, size_t len);



#endif

tools/bpf/bpftool/prog.c

+68 −2
Original line number Diff line number Diff line
@@ -385,7 +385,7 @@ static void print_insn(struct bpf_verifier_env *env, const char *fmt, ...) 
	va_end(args);

}



static void dump_xlated(void *buf, unsigned int len, bool opcodes)

static void dump_xlated_plain(void *buf, unsigned int len, bool opcodes)

{

	struct bpf_insn *insn = buf;

	bool double_insn = false;
@@ -414,6 +414,69 @@ static void dump_xlated(void *buf, unsigned int len, bool opcodes) 
	}

}



static void print_insn_json(struct bpf_verifier_env *env, const char *fmt, ...)

{

	unsigned int l = strlen(fmt);

	char chomped_fmt[l];

	va_list args;



	va_start(args, fmt);

	if (l > 0) {

		strncpy(chomped_fmt, fmt, l - 1);

		chomped_fmt[l - 1] = '\0';

	}

	jsonw_vprintf_enquote(json_wtr, chomped_fmt, args);

	va_end(args);

}



static void dump_xlated_json(void *buf, unsigned int len, bool opcodes)

{

	struct bpf_insn *insn = buf;

	bool double_insn = false;

	unsigned int i;



	jsonw_start_array(json_wtr);

	for (i = 0; i < len / sizeof(*insn); i++) {

		if (double_insn) {

			double_insn = false;

			continue;

		}

		double_insn = insn[i].code == (BPF_LD | BPF_IMM | BPF_DW);



		jsonw_start_object(json_wtr);

		jsonw_name(json_wtr, "disasm");

		print_bpf_insn(print_insn_json, NULL, insn + i, true);



		if (opcodes) {

			jsonw_name(json_wtr, "opcodes");

			jsonw_start_object(json_wtr);



			jsonw_name(json_wtr, "code");

			jsonw_printf(json_wtr, "\"0x%02hhx\"", insn[i].code);



			jsonw_name(json_wtr, "src_reg");

			jsonw_printf(json_wtr, "\"0x%hhx\"", insn[i].src_reg);



			jsonw_name(json_wtr, "dst_reg");

			jsonw_printf(json_wtr, "\"0x%hhx\"", insn[i].dst_reg);



			jsonw_name(json_wtr, "off");

			print_hex_data_json((uint8_t *)(&insn[i].off), 2);



			jsonw_name(json_wtr, "imm");

			if (double_insn && i < len - 1)

				print_hex_data_json((uint8_t *)(&insn[i].imm),

						    12);

			else

				print_hex_data_json((uint8_t *)(&insn[i].imm),

						    4);

			jsonw_end_object(json_wtr);

		}

		jsonw_end_object(json_wtr);

	}

	jsonw_end_array(json_wtr);

}



static int do_dump(int argc, char **argv)

{

	struct bpf_prog_info info = {};
@@ -523,7 +586,10 @@ static int do_dump(int argc, char **argv) 
		if (member_len == &info.jited_prog_len)

			disasm_print_insn(buf, *member_len, opcodes);

		else

			dump_xlated(buf, *member_len, opcodes);

			if (json_output)

				dump_xlated_json(buf, *member_len, opcodes);

			else

				dump_xlated_plain(buf, *member_len, opcodes);

	}



	free(buf);

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