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