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https://github.com/zephyrproject-rtos/zephyr
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8aa6ae43ce
This commit introduces support for an alternate linking method in the LLEXT subsystem, called "SLID" (short for Symbol Link Identifier), enabled by the CONFIG_LLEXT_EXPORT_BUILTINS_BY_SLID Kconfig option. SLID-based linking uses a unique identifier (integer) to identify exported symbols, instead of using the symbol name as done currently. This approach provides several benefits: * linking is faster because the comparison operation to determine whether we found the correct symbol in the export table is now an integer compare, instead of a string compare * binary size is reduced as symbol names can be dropped from the binary * confidentiality is improved as a side-effect, as symbol names are no longer present in the binary Signed-off-by: Mathieu Choplain <mathieu.choplain@st.com>
66 lines
1.9 KiB
Python
Executable File
66 lines
1.9 KiB
Python
Executable File
#!/usr/bin/env python3
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#
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# Copyright (c) 2024 STMicroelectronics
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# SPDX-License-Identifier: Apache-2.0
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"""
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This file implements the Symbol Link Identifer (SLID)
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generation code, for use by the LLEXT subsystem.
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SLID-based linking is enabled by the Kconfig
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option 'CONFIG_LLEXT_EXPORT_BUILTINS_BY_SLID'.
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When executed as a script, this file can be used as
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an interactive prompt to calculate the SLID of arbitrary
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symbols, which can be useful for debugging purposes.
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IMPLEMENTATION NOTES:
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Currently, SLIDs are generated by taking the first
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[pointer size] bytes of the symbol name's SHA-256
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hash, taken in big-endian order.
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This ordering provides one advantage: the 32-bit
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SLID for an export is present in the top 32 bits of
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the 64-bit SLID for the same export.
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"""
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from hashlib import sha256
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def generate_slid(symbol_name: str, slid_size: int) -> int:
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"""
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Generates the Symbol Link Identifier (SLID) for a symbol.
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symbol_name: Name of the symbol for which to generate a SLID
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slid_side: Size of the SLID in bytes (4/8)
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"""
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if slid_size not in (4, 8):
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raise AssertionError(f"Invalid SLID size {slid_size}")
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m = sha256()
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m.update(symbol_name.encode("utf-8"))
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hash = m.digest()
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return int.from_bytes(hash[0:slid_size], byteorder='big', signed=False)
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def format_slid(slid: int, slid_size: int) -> str:
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if slid_size == 4:
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fmt = f"0x{slid:08X}"
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elif slid_size == 8:
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fmt = f"0x{slid:016X}"
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return fmt
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def repl():
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while True:
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sym_name = input("Symbol name? ")
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slid32 = generate_slid(sym_name, 4)
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slid64 = generate_slid(sym_name, 8)
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print(f" 32-bit SLID for '{sym_name}': {format_slid(slid32, 4)}")
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print(f" 64-bit SLID for '{sym_name}': {format_slid(slid64, 8)}")
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print()
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if __name__ == "__main__":
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print("LLEXT SLID calculation REPL")
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print("Press ^C to exit.")
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try:
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repl()
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except KeyboardInterrupt:
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print()
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