109 lines
3.9 KiB
Python
Executable File
109 lines
3.9 KiB
Python
Executable File
#!/usr/bin/env python3
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# Small script to print all options available inside a built kernel.
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# fmt: off
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import sys
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from elftools.elf.elffile import ELFFile
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SIZEOF_PTR = 8
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SIZEOF_STRUCT = 40
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ENDIAN = "little"
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if __name__ == "__main__":
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if len(sys.argv) < 2:
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print("Provide a path to the kernel binary to use")
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sys.exit(1)
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with open(sys.argv[1], "rb") as elffile:
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file = ELFFile(elffile)
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section = file.get_section_by_name(".cmdline")
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if section == None:
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sys.exit(1)
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cmdline_data = section.data()
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num_options = int(section.data_size / SIZEOF_PTR)
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print(f"Kernel contains {num_options} options:")
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for i in range(num_options):
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# Read "struct cmdline_option*"
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addr = int.from_bytes(cmdline_data[(i * SIZEOF_PTR) :][:SIZEOF_PTR], byteorder=ENDIAN)
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elffile.seek(next(file.address_offsets(start=addr)))
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option = elffile.read(SIZEOF_STRUCT)
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# Name
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name = ""
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name_ptr = int.from_bytes(option[0:][:SIZEOF_PTR], byteorder=ENDIAN)
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elffile.seek(next(file.address_offsets(start=name_ptr)))
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while True:
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b = int.from_bytes(elffile.read(1))
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if b == 0:
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break
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name += chr(b)
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# Description
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desc = ""
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desc_ptr = int.from_bytes(option[8:][:SIZEOF_PTR], byteorder=ENDIAN)
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elffile.seek(next(file.address_offsets(start=desc_ptr)))
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while True:
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b = int.from_bytes(elffile.read(1))
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if b == 0:
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break
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desc += chr(b)
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# Type
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kind_str = "unknown"
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kind = int.from_bytes(option[16:][:4], byteorder=ENDIAN)
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match kind:
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case 0:
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kind_str = "string"
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case 1:
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kind_str = "bool"
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case 2:
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kind_str = "integer"
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case 2:
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kind_str = "unsigned integer"
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# Skip function pointer
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# Allowed values
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limit = ""
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limit_ptr = int.from_bytes(option[32:][:SIZEOF_PTR], byteorder=ENDIAN)
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if limit_ptr != 0:
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elffile.seek(next(file.address_offsets(start=limit_ptr)))
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match kind:
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case 0:
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limit = []
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i = 0
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while True:
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ptr = next(file.address_offsets(start=limit_ptr + i * SIZEOF_PTR))
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elffile.seek(ptr)
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str_ptr = int.from_bytes(elffile.read(SIZEOF_PTR), byteorder=ENDIAN)
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if str_ptr == 0:
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break
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strstr_off = next(file.address_offsets(start=str_ptr))
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val = ""
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elffile.seek(strstr_off)
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while True:
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b = int.from_bytes(elffile.read(1))
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if b == 0:
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break
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val += chr(b)
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i += 1
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limit.append(val)
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case 2:
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min = int.from_bytes(elffile.read(SIZEOF_PTR), byteorder=ENDIAN, signed=True)
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max = int.from_bytes(elffile.read(SIZEOF_PTR), byteorder=ENDIAN)
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limit = f"[{min}, {max}]"
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case 3:
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min = int.from_bytes(elffile.read(SIZEOF_PTR), byteorder=ENDIAN)
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max = int.from_bytes(elffile.read(SIZEOF_PTR), byteorder=ENDIAN)
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limit = f"[{min}, {max}]"
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print(f"- {name}:\t{desc} ({kind_str}) {limit if len(limit) != 0 else ""}")
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