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: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 68 insertions, 2 deletions

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index f373f2baef5a..43e49799a624 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -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);