/pahole-fmt

Output formatter for Pahole (prints data structure layout from debug info)

Primary LanguageRubyMIT LicenseMIT

Pahole-fmt

Reformats output of Pahole utility. Prints fields of structs and unions based on compiled debugging info, including type information where there is room. Empty space (padding) is denoted using X's.

Examples

Source code:

struct foo {
    char   a;
    bool   b;
    int    c;
    double d;
};

union bar {
    char   a;
    bool   b;
    int    c;
    double d;
};

Formatted output:

struct foo:

0               4               8               12              16
|               |               |               |               |
-----------------------------------------------------------------
| a | b |#######|    c : int    |          d : double           |
-----------------------------------------------------------------


union bar:

0               4               8
|               |               |
-----
| a |
-----
| b |
-----------------
|    c : int    |
---------------------------------
|          d : double           |
---------------------------------

Source code:

#define NUMREGS 15
typedef int64_t y86_reg_t;
typedef int32_t y86_stat_t;

typedef struct y86 {

    y86_reg_t reg[NUMREGS];     // 64-bit general-purpose registers

    bool zf;                    // zero flag
    bool sf;                    // negative flag
    bool of;                    // overflow flag

    y86_reg_t pc;               // program counter
    y86_stat_t stat;            // program status

} y86_t;

Formatted output:

struct y86:

0               4               8               12              16
|               |               |               |               |
-----------------------------------------------------------------
|                      reg[15] : y86_reg_t                      |
-----------------------------------------------------------------
|                                                               |
-----------------------------------------------------------------
|                                                               |
-----------------------------------------------------------------
|                                                               |
-----------------------------------------------------------------
|                                                               |
-----------------------------------------------------------------
|                                                               |
-----------------------------------------------------------------
|                                                               |
-----------------------------------------------------------------
|                               |zf |sf |of |###################|
-----------------------------------------------------------------
|        pc : y86_reg_t         |     stat      |
-------------------------------------------------

Source code:

typedef uint64_t address_t;

typedef struct y86_inst {

    uint8_t opcode;             // icode:ifun/fn

    // enumerations
    y86_inst_class_t icode;     // icode
    y86_cmov_t cmov;            // ifun/fn  (cmovXX only)
    y86_op_t op;                // ifun/fn  (OPq only)
    y86_jump_t jump;            // ifun/fn  (jXX only)
    y86_iotrap_t id;            // trap id  (iotrap only)

    // 32-bit unsigned
    y86_regnum_t ra;            // rA
    y86_regnum_t rb;            // rB

    address_t dest;             // Dest     (jXX and call only)
    int64_t v;                  // V        (irmovq only)
    int64_t d;                  // D        (rmmovq and mrmovq only)

    uint8_t size;               // hard-coded for each instruction

} y86_inst_t;

Formatted output:

struct y86_inst:

0               4               8               12              16
|               |               |               |               |
-----------------------------------------------------------------
|opc|###########|     icode     |     cmov      | op : y86_op_t |
-----------------------------------------------------------------
|     jump      |      id       |      ra       |      rb       |
-----------------------------------------------------------------
|       dest : address_t        |          v : int64_t          |
-----------------------------------------------------------------
|          d : int64_t          |siz|
-------------------------------------

Installing Pahole-fmt

This utility depends on the availability of the pahole utility, so follow the directions in that repository for downloading, compiling, and installing Pahole.

After Pahole is available, simply clone this repository and make sure the pahole-fmt.rb script is in your executable path.

Using Pahole-fmt

Just run pahole on your binary executable and redirect the output through this utility. For example, if both of them are in your path, you should be able to run a command similar to this:

pahole <your-executable> | pahole-fmt.rb

Your executable must be compiled with debugging information (-g in most compilers), and your structs and unions must be named. C++ classes will be detected as structs (e.g., data layout only).

Getting Involved

To get involved, submit an issue or email the author directly.

Contributing

To contribute, submit a pull request or email the author directly.

Release

This software is released under the MIT license.

Copyright (C) 2019 Michael O. Lam