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Sym2srec

Sym2srec is a CLI program that copies both sections ".symtab" and ".strtab" of an executable file into loadable segments of a new executable file. The goal is to allow an external program to run in main memory (dynamic loading).

The software uses a destination address and an ELF32 file (.elf) as inputs. It produces an S-Record file (.srec) as output. A hash table (.gnu hash) is also produced and copied into the S-Record file to accelerate symbol relocations.

Usage

Sym2srec can be run from the command line interface with the following command:

sym2srec $(BUILD_ARTIFACT_NAME).elf $(OUTPUT_ARTIFACT_NAME).srec $(SYMBOL_BASE_ADDR)

Options are:

$(BUILD_ARTIFACT_NAME).elf: executable file containing the symbols to export to the srec file. Format of file is 32bits.

$(OUTPUT_ARTIFACT_NAME).srec: S-Record file to create.

$(SYMBOL_BASE_ADDR): base address where symbols should be copied. Format is 8 digits and 4 bytes alignment (ex: 0x002C0000).

Example:

sym2srec myApps.elf ../build/myApps.srec 0x002C0000

Strip

Before running the command, the executable file may be strip with the following command line:

strip --discard-all --strip-debug $(STRIP_ARTIFACT_NAME).elf

This command removes all non-global and debug symbols from the artefact. Strip is a GNU Development Tools, it can be found in the GNU Development Toolchain (arm-none-eabi-strip, ...).

Symbol Resolution

The wiki in the repository describes how a dynamic loader may load external applications by resolving symbols.

Build

Sym2srec can be built using the makefile file on the repository. The variable TOOLCHAIN_PATH must be updated with the path of the MinGW-W64 toolchain.

First issue a make clean command then build the target with make all.

Currently versions of compiler used are the followings:

  • gcc (x86_64-posix-sjlj-rev0, Built by MinGW-W64 project) 8.1.0
  • g++ (x86_64-posix-sjlj-rev0, Built by MinGW-W64 project) 8.1.0

Please note, the application must be built in 32bits (option -m32).

License

Copyright (C) 2024 RENARD Mathieu. All rights reserved.

Sym2srec is free software; There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

The content of this repository is bound by the BSD-3-Clause license.