├── README.md
├── gdb_newlib.py
└── requirements.txt


/README.md:
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 1 | This repo will hopefully eventually hold a collection of useful gdb-python scripts for debug.
 2 | 
 3 | If you don't know much about GDBs python scripting API check out [this writeup](https://github.com/chrisc11/debug-tips/blob/master/gdb/python-linked-list.md)!
 4 | 
 5 | PS: I tried to search the interwebs first for a pre-existing implementation for commands added but
 6 | could not find anything. If you know of a repo that provides similar functionality for any of the
 7 | command you see, do let me know!
 8 | 
 9 | 
10 | # Available Commands
11 | 
12 | ## Newlib
13 | 
14 | `newlib heapdump` - Pretty prints the blocks in a newlib libc heap
15 | 


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/gdb_newlib.py:
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 1 | try:
 2 |     import gdb
 3 | except ImportError:
 4 |     error_str = """
 5 |     This script can only be run within gdb!
 6 |     You need to 'source gdb_newlib.py' from (gdb) or in your init file
 7 |     """
 8 |     raise Exception(error_str)
 9 | 
10 | from prettytable import PrettyTable
11 | 
12 | 
13 | class NewlibCommand(gdb.Command):
14 |     """Utility commands for debugging newlib"""
15 | 
16 |     def __init__(self):
17 |         super(NewlibCommand, self).__init__(
18 |                 'newlib', gdb.COMMAND_USER, gdb.COMPLETE_NONE, prefix=True)
19 | 
20 |     def invoke(self, arg, from_tty):
21 |         gdb.execute('help newlib')
22 | NewlibCommand()
23 | 
24 | 
25 | class NewlibDefaultHeapDump(gdb.Command):
26 |     """Prints the current blocks in a newlib heap
27 | 
28 |     Newlib uses a heap implementaion written by Doug Lea. You can find the implementation as part
29 |     of the newlib sources here:
30 |         https://github.com/bminor/newlib/blob/master/newlib/libc/stdlib/mallocr.c#L11
31 | 
32 |     This python-gdb utility command attempts to print all the malloc_chunk's that currently make up
33 |     the heap in an easy to read format. This can be useful to get a better understanding of
34 |     fragmentation and free space
35 | 
36 |     Note: The function currently assumes you are linking newlib with debug so it can find the
37 |     following symbol information:
38 |          * '__malloc_sbrk_base' static
39 |          * '__malloc_av_' static
40 |          * 'struct malloc_chunk' type
41 | 
42 |     This could probably be improved in the future by also allowing a user to specify this info via
43 |     command args and loading the 'struct malloc_chunk' symbol definition into gdb as part of a
44 |     dummy elf
45 |     """
46 |     def __init__(self):
47 |         super(NewlibDefaultHeapDump, self).__init__('newlib heapdump', gdb.COMMAND_USER)
48 | 
49 |     def invoke(self, unicode_args, from_tty):
50 |         results = PrettyTable()
51 |         results.field_names = list(['Block Addr', 'User Data Start', 'Tot Size (bytes)'])
52 | 
53 |         heap_start = gdb.parse_and_eval('__malloc_sbrk_base')
54 | 
55 |         malloc_chunk_ptr_type = gdb.lookup_type("struct malloc_chunk").pointer()
56 |         next_malloc_chunk_ptr = heap_start
57 |         malloc_chunk = next_malloc_chunk_ptr.cast(malloc_chunk_ptr_type)
58 |         running_total = 0
59 |         bytes_free = 0
60 |         blocks_allocated = 0
61 | 
62 |         top_bin = gdb.parse_and_eval('__malloc_av_[2]')
63 | 
64 |         while True:
65 |             flags = malloc_chunk['size'] & 0x3
66 |             block_size = malloc_chunk['size'] & ~0x3
67 |             running_total += block_size
68 |             next_malloc_chunk_ptr += block_size
69 |             next_malloc_chunk = next_malloc_chunk_ptr.cast(malloc_chunk_ptr_type)
70 |             blocks_allocated += 1
71 | 
72 |             # Check the PREV_INUSE flag to figure out if the current block is free
73 |             in_use = next_malloc_chunk['size'] & 0x1
74 |             user_data = '0x%x' % malloc_chunk['fd'].address if in_use else 'FREE'
75 |             bytes_free += block_size if not in_use else 0
76 | 
77 |             results.add_row([str(malloc_chunk), user_data, str(block_size)])
78 | 
79 |             if top_bin == malloc_chunk:  # We are done
80 |                 break
81 |             malloc_chunk = next_malloc_chunk
82 | 
83 |         print(results)
84 |         print("%d blocks: %d/%d bytes free" % (blocks_allocated, bytes_free, running_total))
85 | 
86 | NewlibDefaultHeapDump()
87 | 


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/requirements.txt:
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1 | prettytable >= 0.7.2
2 | 


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