338 lines
12 KiB
Python
Executable file
338 lines
12 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 tempfile
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import argparse
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from enum import Enum
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from shared_python import elf_so_deps, do_remote, is_newer
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from extract_pc import generate_pc_list
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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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class SwitchGenPolicy(Enum):
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''' The various switch generation policies possible '''
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SWITCH_PER_FUNC = '--switch-per-func'
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GLOBAL_SWITCH = '--global-switch'
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class Config:
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''' Holds the run's settings '''
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def __init__(self,
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output,
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objects,
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sw_gen_policy=SwitchGenPolicy.GLOBAL_SWITCH,
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force=False,
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use_pc_list=False,
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c_opt_level='3',
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enable_deref_arg=False,
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cc_debug=False,
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remote=None):
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self.output = output
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self.objects = objects
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self.sw_gen_policy = sw_gen_policy
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self.force = force
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self.use_pc_list = use_pc_list
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self.c_opt_level = c_opt_level
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self.enable_deref_arg = enable_deref_arg
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self.cc_debug = cc_debug
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self.remote = remote
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def dwarf_assembly_args(self):
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''' Arguments to `dwarf_assembly` '''
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out = []
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out.append(self.sw_gen_policy.value)
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if self.enable_deref_arg:
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out.append('--enable-deref-arg')
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return out
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def cc_opts(self):
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''' Options to pass to the C compiler '''
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out = ['-fPIC']
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if self.cc_debug:
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out.append('-g')
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out.append(self.opt_level())
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return out
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def opt_level(self):
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''' The optimization level to pass to gcc '''
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return '-O{}'.format(self.c_opt_level)
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def gen_dw_asm_c(obj_path, out_path, config, pc_list_path=None):
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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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dw_assembly_args = config.dwarf_assembly_args()
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if pc_list_path is not None:
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dw_assembly_args += ['--pc-list', pc_list_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] + dw_assembly_args) \
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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 exn:
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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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exn.returncode))
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def resolve_symlink_chain(objpath):
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''' Resolves a symlink chain. This returns a pair `(new_obj, chain)`,
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`new_obj` being the canonical path for `objpath`, and `chain` being a list
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representing the path followed, eg. `[(objpath, a), (a, b), (b, new_obj)]`.
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The goal of this function is to allow reproducing symlink architectures at
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the eh_elf level. '''
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chain = []
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out_path = objpath
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while os.path.islink(out_path):
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new_path = os.readlink(out_path)
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if not os.path.isabs(new_path):
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new_path = os.path.join(os.path.dirname(out_path), new_path)
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chain.append((out_path, new_path))
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out_path = new_path
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return (out_path, chain)
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def gen_eh_elf(obj_path, config):
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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 config.output is None:
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out_dir = '.'
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else:
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out_dir = config.output
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def to_eh_elf_path(so_path, base=False):
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''' Transform a library path into its eh_elf counterpart '''
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base_path = os.path.basename(so_path) + '.eh_elf'
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if base:
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return base_path
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return os.path.join(out_dir, base_path + '.so')
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obj_path, link_chain = resolve_symlink_chain(obj_path)
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print("> {}...".format(os.path.basename(obj_path)))
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link_chain = map(
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lambda elt:
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(to_eh_elf_path(elt[0]),
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os.path.basename(to_eh_elf_path(elt[1]))),
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link_chain)
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out_base_name = to_eh_elf_path(obj_path, base=True)
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out_so_path = to_eh_elf_path(obj_path, base=False)
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pc_list_dir = os.path.join(out_dir, 'pc_list')
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if is_newer(out_so_path, obj_path) and not config.force:
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return # The object is recent enough, no need to recreate it
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with tempfile.TemporaryDirectory() as compile_dir:
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# Generate PC list
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pc_list_path = None
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if config.use_pc_list:
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pc_list_path = \
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os.path.join(pc_list_dir, out_base_name + '.pc_list')
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os.makedirs(pc_list_dir, exist_ok=True)
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print('\tGenerating PC list…')
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generate_pc_list(obj_path, pc_list_path)
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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, config, pc_list_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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if config.remote:
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remote_out = do_remote(
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config.remote,
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[
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C_BIN,
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'-o', out_base_name + '.o',
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'-c', out_base_name + '.c'
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] + config.cc_opts(),
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send_files=[c_path],
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retr_files=[(out_base_name + '.o', o_path)])
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call_rc = 1 if remote_out is None else 0
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else:
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call_rc = subprocess.call(
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[C_BIN, '-o', o_path, '-c', c_path,
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config.opt_level(), '-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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# Re-create symlinks
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for elt in link_chain:
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if os.path.exists(elt[0]):
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if not os.path.islink(elt[0]):
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raise Exception(
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"{}: file already exists and is not a symlink.".format(
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elt[0]))
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os.remove(elt[0])
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os.symlink(elt[1], elt[0])
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def gen_all_eh_elf(obj_path, config):
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''' Call `gen_eh_elf` on obj_path and all its dependencies '''
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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, config)
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def gen_eh_elfs(obj_path,
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out_dir,
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global_switch=True,
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deps=True,
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remote=None):
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''' Call gen{_all,}_eh_elf with args setup accordingly with the given
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options '''
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switch_gen_policy = (
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SwitchGenPolicy.GLOBAL_SWITCH if global_switch
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else SwitchGenPolicy.SWITCH_PER_FUNC
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)
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config = Config(
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out_dir,
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[obj_path],
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sw_gen_policy=switch_gen_policy,
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remote=remote,
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)
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if deps:
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return gen_all_eh_elf([obj_path], config)
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else:
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return gen_eh_elf([obj_path], config)
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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('--remote', metavar='ssh_args',
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help=("Execute the heavyweight commands on the remote "
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"machine, using `ssh ssh_args`."))
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parser.add_argument('--use-pc-list', action='store_true',
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help=("Generate a PC list using `extract_pc.py` for "
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"each processed ELF file, and call "
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"dwarf-assembly accordingly."))
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parser.add_argument('--force', '-f', action='store_true',
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help=("Force re-generation of the output files, even "
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"when those files are newer than the target "
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"ELF."))
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parser.add_argument('--enable-deref-arg', action='store_true',
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help=("Pass the `--enable-deref-arg` to "
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"dwarf-assembly, enabling an extra `deref` "
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"argument for each lookup function, allowing "
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"to work on remote address spaces."))
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parser.add_argument("-g", "--cc-debug", action='store_true',
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help=("Compile the source file with -g for easy "
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"debugging"))
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# c_opt_level
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opt_level_grp = parser.add_mutually_exclusive_group()
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opt_level_grp.add_argument('-O0', action='store_const', const='0',
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dest='c_opt_level',
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help=("Compile C file with this optimization "
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"level."))
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opt_level_grp.add_argument('-O1', action='store_const', const='1',
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dest='c_opt_level',
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help=("Compile C file with this optimization "
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"level."))
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opt_level_grp.add_argument('-O2', action='store_const', const='2',
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dest='c_opt_level',
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help=("Compile C file with this optimization "
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"level."))
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opt_level_grp.add_argument('-O3', action='store_const', const='3',
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dest='c_opt_level',
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help=("Compile C file with this optimization "
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"level."))
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opt_level_grp.add_argument('-Os', action='store_const', const='s',
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dest='c_opt_level',
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help=("Compile C file with this optimization "
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"level."))
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opt_level_grp.set_defaults(c_opt_level='3')
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switch_gen_policy = \
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parser.add_mutually_exclusive_group(required=True)
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switch_gen_policy.add_argument('--switch-per-func',
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dest='sw_gen_policy',
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action='store_const',
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const=SwitchGenPolicy.SWITCH_PER_FUNC,
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help=("Passed to dwarf-assembly."))
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switch_gen_policy.add_argument('--global-switch',
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dest='sw_gen_policy',
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action='store_const',
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const=SwitchGenPolicy.GLOBAL_SWITCH,
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help=("Passed to dwarf-assembly."))
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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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config = Config(
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args.output,
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args.object,
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args.sw_gen_policy,
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args.force,
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args.use_pc_list,
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args.c_opt_level,
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args.enable_deref_arg,
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args.cc_debug,
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args.remote,
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)
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for obj in args.object:
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args.gen_func(obj, config)
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if __name__ == "__main__":
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main()
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