{simple,shoddy,smart} minsize-oriented linker
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import glob
import os.path
import subprocess
import struct
import sys
from smolshared import *
def decide_arch(inpfiles):
archs=set({})
for fp in inpfiles:
with open(fp, 'rb') as ff:
_ = ff.read(16) # ei_ident
_ = ff.read( 2) # ei_type
machine = ff.read(2) # ei_machine
machnum = struct.unpack('<H', machine)[0]
archs.add(machnum)
if len(archs) != 1:
eprintf("Input files have multiple architectures, can't link this...")
sys.exit(1)
archn = list(archs)[0]
if archn not in archmagic:
eprintf("Unknown architecture number " + str(archn) + \
". Consult elf.h and rebuild your object files.")
return archmagic[archn]
def build_reloc_typ_table(reo):
relocs = dict({})
for s in reo.decode('utf-8').splitlines():
stuff = s.split()
# prolly a 'header' line
if len(stuff) < 5:
continue
# yes, we're assuming every reference to the same symbol will use the
# same relocation type. if this isn't the case, your compiler flags are
# stupid
relocs[stuff[4]] = stuff[2]
return relocs
def get_needed_syms(readelf_bin, inpfiles):
output = subprocess.check_output([readelf_bin, '-s', '-W']+inpfiles,
stderr=subprocess.DEVNULL)
outrel = subprocess.check_output([readelf_bin, '-r', '-W']+inpfiles,
stderr=subprocess.DEVNULL)
relocs = build_reloc_typ_table(outrel)
syms=set({})
for entry in output.decode('utf-8').splitlines():
stuff = entry.split()
if len(stuff)<8: continue
if stuff[4] == "GLOBAL" and stuff[6] == "UND" and len(stuff[7])>0 \
and stuff[7] in relocs:
syms.add((stuff[7], relocs[stuff[7]]))
#needgot = False
#if "_GLOBAL_OFFSET_TABLE_" in syms:
# needgot = True
# syms.remove("_GLOBAL_OFFSET_TABLE_")
return syms#, needgot
def format_cc_path_line(entry):
category, path = entry.split(': ', 1)
path = path.lstrip('=')
return (category, list(set(os.path.realpath(p) \
for p in path.split(':') if os.path.isdir(p))))
def get_cc_paths(cc_bin):
bak = os.environ.copy()
os.environ['LANG'] = "C" # DON'T output localized search dirs!
output = subprocess.check_output([cc_bin, '-print-search-dirs'],
stderr=subprocess.DEVNULL)
os.environ = bak
outputpairs = list(map(format_cc_path_line,
output.decode('utf-8').splitlines()))
for category, path in outputpairs: paths[category] = path
if 'libraries' not in paths: # probably localized... sigh
# monkeypatch, assuming order...
paths = {}
paths['install' ] = outputpairs[0][1]
paths['programs' ] = outputpairs[1][1]
paths['libraries'] = outputpairs[2][1]
return paths
def is_valid_elf(f):
with open(f, 'rb') as ff: return ff.read(4) == b'\x7FELF'
def find_lib(spaths, wanted):
for p in spaths:
for f in glob.glob(glob.escape(p + '/lib' + wanted) + '.so*'):
if os.path.isfile(f) and is_valid_elf(f): return f
for f in glob.glob(glob.escape(p + '/' + wanted) + '.so*'):
if os.path.isfile(f) and is_valid_elf(f): return f
#for f in glob.glob(glob.escape(p) + '/lib' + wanted + '.a' ): return f
#for f in glob.glob(glob.escape(p) + '/' + wanted + '.a' ): return f
eprintf("E: couldn't find library '" + wanted + "'.")
sys.exit(1)
def find_libs(spaths, wanted): return map(lambda l: find_lib(spaths, l), wanted)
def find_symbol(scanelf_bin, libraries, libnames, symbol):
output = subprocess.check_output([scanelf_bin, '-B', '-F' '%s %S', '-s', \
'+{}'.format(symbol)] + libraries, stderr=subprocess.DEVNULL)
for entry in output.decode('utf-8').splitlines():
sym, soname, path = entry.split(' ', 2)
if symbol in sym.split(',') and \
any(soname.startswith('lib'+l) for l in libnames):
return soname