155 lines
4.6 KiB
Python
Executable file
155 lines
4.6 KiB
Python
Executable file
#!/usr/bin/env python3
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"""
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Generates the `.eh_frame` equivalent in C code of the given ELF file, and
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all the shared objects it depends upon.
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"""
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import os
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import sys
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import subprocess
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import re
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import tempfile
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import argparse
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DWARF_ASSEMBLY_BIN = os.path.join(
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os.path.dirname(os.path.abspath(sys.argv[0])),
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'dwarf-assembly')
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C_BIN = (
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'gcc' if 'C' not in os.environ
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else os.environ['C'])
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def elf_so_deps(path):
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''' Get the list of shared objects dependencies of the given ELF object.
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This is obtained by running `ldd`. '''
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deps_list = []
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try:
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ldd_output = subprocess.check_output(['/usr/bin/ldd', path]) \
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.decode('utf-8')
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ldd_re = re.compile(r'^.* => (.*) \(0x[0-9a-fA-F]*\)$')
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ldd_lines = ldd_output.strip().split('\n')
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for line in ldd_lines:
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line = line.strip()
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match = ldd_re.match(line)
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if match is None:
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continue # Just ignore that line — it might be eg. linux-vdso
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deps_list.append(match.group(1))
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return deps_list
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except subprocess.CalledProcessError as e:
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raise Exception(
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("Cannot get dependencies for {}: ldd terminated with exit code "
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"{}.").format(path, e.returncode))
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def gen_dw_asm_c(obj_path, out_path):
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''' Generate the C code produced by dwarf-assembly from `obj_path`, saving
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it as `out_path` '''
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try:
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with open(out_path, 'w') as out_handle:
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# TODO enhance error handling
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dw_asm_output = subprocess.check_output(
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[DWARF_ASSEMBLY_BIN, obj_path]) \
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.decode('utf-8')
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out_handle.write(dw_asm_output)
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except subprocess.CalledProcessError as e:
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raise Exception(
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("Cannot generate C code from object file {} using {}: process "
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"terminated with exit code {}.").format(
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obj_path,
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DWARF_ASSEMBLY_BIN,
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e.returncode))
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def gen_eh_elf(obj_path, out_dir=None):
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''' Generate the eh_elf corresponding to `obj_path`, saving it as
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`out_dir/$(basename obj_path).eh_elf.so` (or in the current working
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directory if out_dir is None) '''
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if out_dir is None:
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out_dir = '.'
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print("> {}...".format(os.path.basename(obj_path)))
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out_base_name = os.path.basename(obj_path) + '.eh_elf'
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out_so_path = os.path.join(out_dir, (out_base_name + '.so'))
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try:
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so_mtime = os.path.getmtime(out_so_path)
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obj_mtime = os.path.getmtime(obj_path)
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if obj_mtime < so_mtime:
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return # The object is recent enough, no need to recreate it
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except OSError:
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pass
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with tempfile.TemporaryDirectory() as compile_dir:
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# Generate the C source file
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print("\tGenerating C…")
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c_path = os.path.join(compile_dir, (out_base_name + '.c'))
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gen_dw_asm_c(obj_path, c_path)
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# Compile it into a .o
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print("\tCompiling into .o…")
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o_path = os.path.join(compile_dir, (out_base_name + '.o'))
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call_rc = subprocess.call(
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[C_BIN, '-o', o_path, '-c', c_path, '-O3', '-fPIC'])
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if call_rc != 0:
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raise Exception("Failed to compile to a .o file")
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# Compile it into a .so
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print("\tCompiling into .so…")
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call_rc = subprocess.call(
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[C_BIN, '-o', out_so_path, '-shared', o_path])
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if call_rc != 0:
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raise Exception("Failed to compile to a .so file")
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def gen_all_eh_elf(obj_path, out_dir=None):
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''' Call `gen_eh_elf` on obj_path and all its dependencies '''
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if out_dir is None:
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out_dir = '.'
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deps = elf_so_deps(obj_path)
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deps.append(obj_path)
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for dep in deps:
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gen_eh_elf(dep, out_dir)
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def process_args():
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''' Process `sys.argv` arguments '''
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parser = argparse.ArgumentParser(
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description="Compile ELFs into their related eh_elfs",
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)
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parser.add_argument('--deps', action='store_const',
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const=gen_all_eh_elf, default=gen_eh_elf,
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dest='gen_func',
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help=("Also generate eh_elfs for the shared objects "
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"this object depends on"))
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parser.add_argument('-o', '--output', metavar="path",
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help=("Save the generated objects at the given path "
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"instead of the current working directory"))
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parser.add_argument('object', nargs='+',
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help="The ELF object(s) to process")
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return parser.parse_args()
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def main():
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args = process_args()
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for obj in args.object:
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args.gen_func(obj, args.output)
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if __name__ == "__main__":
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main()
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