gen_graph.py

Description

Python command line tool to visualize function-call-flow for a C/C++ program using graphviz dot object and matplotlib.

Directory structure:

├── gallery
│   ├── graph_GNU_MAKE_.png
│   ├── graph_QEMU.png
│   ├── graph_VIM.png
│   ├── some_library_graph.png
│   ├── test.png
│   └── test.svg
├── gen_graph.py
├── LICENSE
├── README.md
├── requiments.txt
└── test
    ├── test.c
    └── test.log

Motivation

I wanted to view call-graph for OS source (written in C, C++) that connected APIs within one layer and APIs across layers. This helps in getting a bigger picture of the source code and makes understanding large code bases QUICK.

Input

Requires data from gdb to get nodes (functions) and edges (function 1 calling function 2).

Output

Di-graph showing relationship between functions across software layers, the "bigger picture".

Usage

There are two parts to the whole process:

1. get data by runnning process under gdb
2. process this data with gen_graph.py

Part I: Get data from GDB

Test code

$  cat test.c
#include<stdio.h>
#include<stdbool.h>
#include<stdlib.h>
#include<time.h>


static void func9(void) { printf("leaf\n"); }

void func8(void) { func9(); }

void func7_1(bool is_true, int *p) { printf("leaf (is_true=%d, ptr=%p\n", is_true, p); }
void func7(void) { func8(); }

void func6(void) { func7(); }

void func5_1(const char* str) { printf("leaf (%s)\n", str); }
void func5(void) {
    func5_1("graph me\n");
    func6();
}

void func4(void) { func5(); }
void func3_1(int a, int b, int c) { printf("leaf\n"); }
void func3(void) {
    func3_1(rand(), rand(), rand());
    func4();
}

void func2_1(int a, int b) { printf("leaf (%d, %d)\n", a, b);}
void func2(void) {
    func2_1(rand(),rand());
    func3();
}
void func1(void) { func2(); }
int main()
{
    srand(time(NULL));
    for(int i=0; i<10; ++i) {
            func1();
    }
        return 0;
}

Enable debugging symbols

$ gcc -g test.c

Start binary under GDB

$ gdb a.out
. . .
Reading symbols from a.out...done.

Insert breakpoints on functions of interest, or to put in every funtion in a file:

(gdb) rbreak test.c:.
Breakpoint 1 at 0x400786: file test/test.c, line 33.
void func1(void);
Breakpoint 2 at 0x400760: file test/test.c, line 30.
void func2(void);
Breakpoint 3 at 0x40073d: file test/test.c, line 28.
void func2_1(int, int);
Breakpoint 4 at 0x400704: file test/test.c, line 24.
void func3(void);
Breakpoint 5 at 0x4006f0: file test/test.c, line 22.
void func3_1(int, int, int);
Breakpoint 6 at 0x4006d7: file test/test.c, line 21.
void func4(void);
Breakpoint 7 at 0x4006c1: file test/test.c, line 17.
void func5(void);
Breakpoint 8 at 0x4006a4: file test/test.c, line 15.
void func5_1(const char *);
Breakpoint 9 at 0x400690: file test/test.c, line 13.
void func6(void);
Breakpoint 10 at 0x400684: file test/test.c, line 11.
void func7(void);
Breakpoint 11 at 0x400664: file test/test.c, line 10.
void func7_1(_Bool, int *);
Breakpoint 12 at 0x40064b: file test/test.c, line 8.
void func8(void);
Breakpoint 13 at 0x400796: file test/test.c, line 36.
int main();
Breakpoint 14 at 0x40063a: file test/test.c, line 7.
static void func9(void);

Enable logging

(gdb) set pagination off
(gdb) set print pretty
(gdb) set logging file ./test.log
(gdb) set logging on
Copying output to ./test.log.

Tell gdb to print backtrace and continue without asking when it hits a breakpoint

(gdb) command
Type commands for breakpoint(s) 1-10, one per line.
End with a line saying just "end".
>bt
>c
>end

Start the program

(gdb) r
Starting program: /home/vagrant/c_code/a.out

Once the program finishes, it would have dumped the logs to the disk in test.log    

Part II: run gen_graph.py on collected data

Dependencies

sudo apt-get install graphviz
sudo python3 -m pip install -r requiments.txt

Run gen_graph.py

$  python3 gen_graph.py
usage: gen_graph.py [-h] -i INPUT_FILE [-f {gdb,objdump}]
gen_graph.py: error: the following arguments are required: -i/--input_file

$  python3 gen_graph.py -i test/test.log
01/02/2021 08:36:58 PM [1] processing gdb bt data
01/02/2021 08:36:58 PM [2] adding nodes, edges, #ofnodes=13
01/02/2021 08:36:59 PM [3] Embedding JS
01/02/2021 08:36:59 PM [4] saving graph to:
01/02/2021 08:36:59 PM       /home/vagrant/dwnlds/gdb_graphs/test.svg
01/02/2021 08:36:59 PM Finished

Open the svg file in a browser

New

• Interactive graphs: Click on a node and entire parent and child chain is highlighted (to reset - reload page - untill I find a better way to do from JS)
• C++ Support
• Node tooltip shows function arguments (max 6)