From: Quentin Monnet <quentin.mon...@netronome.com>

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.mon...@netronome.com>
---
 tools/bpf/bpftool/common.c      | 10 ++++++
 tools/bpf/bpftool/json_writer.c |  8 +++++
 tools/bpf/bpftool/json_writer.h |  2 ++
 tools/bpf/bpftool/main.h        |  1 +
 tools/bpf/bpftool/prog.c        | 70 +++++++++++++++++++++++++++++++++++++++--
 5 files changed, 89 insertions(+), 2 deletions(-)

diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
index df8396a0c400..e7a756b8ee21 100644
--- a/tools/bpf/bpftool/common.c
+++ b/tools/bpf/bpftool/common.c
@@ -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);
+}
diff --git a/tools/bpf/bpftool/json_writer.c b/tools/bpf/bpftool/json_writer.c
index 6b77d288cce2..c6eef76322ae 100644
--- a/tools/bpf/bpftool/json_writer.c
+++ b/tools/bpf/bpftool/json_writer.c
@@ -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;
diff --git a/tools/bpf/bpftool/json_writer.h b/tools/bpf/bpftool/json_writer.h
index 1516aafba59d..0fa2fb1b6351 100644
--- a/tools/bpf/bpftool/json_writer.h
+++ b/tools/bpf/bpftool/json_writer.h
@@ -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);
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index 15927fc9fb31..693fc9710be1 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -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
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);
-- 
2.14.1

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