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tools: add dump-auxv.py
This is a little helper I used when preparing the tests for auxv parsing. Just looking at hexdump output is pretty hard. We could enhance it to display some specific data types better.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
Luca Boccassi
parent
61b69bec8e
commit
85a336f81d
137
tools/dump-auxv.py
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137
tools/dump-auxv.py
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#!/usr/bin/python
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# SPDX-License-Identifier: LGPL-2.1-or-later
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"""
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A program to parse auxv (e.g. /proc/self/auxv).
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By default, current arch is assumed, but options can be used to override the
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endianness and word size.
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"""
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import struct
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import click
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# From /usr/include/elf.h
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AT_AUXV = {
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'AT_NULL' : 0, # End of vector
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'AT_IGNORE' : 1, # Entry should be ignored
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'AT_EXECFD' : 2, # File descriptor of program
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'AT_PHDR' : 3, # Program headers for program
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'AT_PHENT' : 4, # Size of program header entry
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'AT_PHNUM' : 5, # Number of program headers
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'AT_PAGESZ' : 6, # System page size
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'AT_BASE' : 7, # Base address of interpreter
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'AT_FLAGS' : 8, # Flags
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'AT_ENTRY' : 9, # Entry point of program
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'AT_NOTELF' : 10, # Program is not ELF
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'AT_UID' : 11, # Real uid
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'AT_EUID' : 12, # Effective uid
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'AT_GID' : 13, # Real gid
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'AT_EGID' : 14, # Effective gid
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'AT_CLKTCK' : 17, # Frequency of times()
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# Some more special a_type values describing the hardware.
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'AT_PLATFORM' : 15, # String identifying platform.
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'AT_HWCAP' : 16, # Machine-dependent hints about processor capabilities.
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# This entry gives some information about the FPU initialization performed by the kernel.
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'AT_FPUCW' : 18, # Used FPU control word.
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# Cache block sizes.
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'AT_DCACHEBSIZE' : 19, # Data cache block size.
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'AT_ICACHEBSIZE' : 20, # Instruction cache block size.
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'AT_UCACHEBSIZE' : 21, # Unified cache block size.
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# A special ignored value for PPC, used by the kernel to control the
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# interpretation of the AUXV. Must be > 16.
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'AT_IGNOREPPC' : 22, # Entry should be ignored.
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'AT_SECURE' : 23, # Boolean, was exec setuid-like?
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'AT_BASE_PLATFORM' : 24, # String identifying real platforms.
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'AT_RANDOM' : 25, # Address of 16 random bytes.
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'AT_HWCAP2' : 26, # More machine-dependent hints about processor capabilities.
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'AT_EXECFN' : 31, # Filename of executable.
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# Pointer to the global system page used for system calls and other nice things.
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'AT_SYSINFO' : 32,
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'AT_SYSINFO_EHDR' : 33,
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# Shapes of the caches. Bits 0-3 contains associativity; bits 4-7 contains
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# log2 of line size; mask those to get cache size.
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'AT_L1I_CACHESHAPE' : 34,
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'AT_L1D_CACHESHAPE' : 35,
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'AT_L2_CACHESHAPE' : 36,
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'AT_L3_CACHESHAPE' : 37,
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# Shapes of the caches, with more room to describe them.
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# GEOMETRY are comprised of cache line size in bytes in the bottom 16 bits
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# and the cache associativity in the next 16 bits.
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'AT_L1I_CACHESIZE' : 40,
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'AT_L1I_CACHEGEOMETRY' : 41,
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'AT_L1D_CACHESIZE' : 42,
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'AT_L1D_CACHEGEOMETRY' : 43,
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'AT_L2_CACHESIZE' : 44,
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'AT_L2_CACHEGEOMETRY' : 45,
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'AT_L3_CACHESIZE' : 46,
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'AT_L3_CACHEGEOMETRY' : 47,
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'AT_MINSIGSTKSZ' : 51, # Stack needed for signal delivery
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}
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AT_AUXV_NAMES = {v:k for k,v in AT_AUXV.items()}
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@click.command(help=__doc__)
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@click.option('-b', '--big-endian', 'endian',
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flag_value='>',
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help='Input is big-endian')
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@click.option('-l', '--little-endian', 'endian',
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flag_value='<',
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help='Input is little-endian')
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@click.option('-3', '--32', 'field_width',
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flag_value=32,
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help='Input is 32-bit')
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@click.option('-6', '--64', 'field_width',
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flag_value=64,
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help='Input is 64-bit')
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@click.argument('file',
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type=click.File(mode='rb'))
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def dump(endian, field_width, file):
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data = file.read()
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if field_width is None:
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field_width = struct.calcsize('P') * 8
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if endian is None:
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endian = '@'
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width = {32:'II', 64:'QQ'}[field_width]
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format = f'{endian}{width}'
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print(f'# {format=}')
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seen_null = False
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for item in struct.iter_unpack(format, data):
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key, val = item
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name = AT_AUXV_NAMES.get(key, f'unknown ({key})')
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if name.endswith(('UID', 'GID')):
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pref, fmt = '', 'd'
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else:
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pref, fmt = '0x', 'x'
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if seen_null:
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print('# trailing garbarbage after AT_NULL')
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print(f'{name:18} = {pref}{val:{fmt}}')
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if name == 'AT_NULL':
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seen_null = True
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if not seen_null:
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print('# array not terminated with AT_NULL')
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if __name__ == '__main__':
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dump()
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