elf: Hide _init/_fini and use function size from regular object
H.J. Lu proposes hiding _init/_fini symbols and using function sizes from regular objects to improve linker behavior with ELF objects.
H.J. Lu submits version 2 of a patch that aims to improve ELF object handling in the static linker. The changes involve hiding the _init and _fini symbols when they define DT_INIT and DT_FINI to prevent confusion, and using function sizes from regular objects instead of dynamic ones for better accuracy. Changes in v2 include replacing .nops with .space and adjusting testsuite configurations.
- proposer
Submits v2 of a patch to hide _init/_fini symbols and use regular object function sizes, detailing changes to the linker's ELF handling and testsuite.
“1. Hide _init and _fini, when they are used to define DT_INIT and DT_FINI, to avoid confusing static linker and run-time linker with ELF objects with exported _init and _fini. 2. Use function size defined in regular object since function from dynamic object is independent from function defined in regular object.”
In Details
This patch addresses issues in the ELF linker (ld) related to symbol resolution and size calculation for initialization functions. It proposes to hide the linker-generated _init and _fini symbols when they are used to define the DT_INIT and DT_FINI dynamic tags. Additionally, it ensures that the linker uses the size of functions defined in regular object files rather than those from dynamic objects, resolving a discrepancy that could affect linker behavior.
- _init
- A special symbol in ELF executables and shared objects, typically used to initialize a shared library when it is loaded.
- _fini
- A special symbol in ELF executables and shared objects, used to perform cleanup operations when a shared library is unloaded.
- DT_INIT
- A dynamic tag in the ELF header that specifies the address of the initialization function for a shared object.
- DT_FINI
- A dynamic tag in the ELF header that specifies the address of the termination function for a shared object.
- ELF objects
- Executable and Linkable Format files, a standard file format for executables, object code, shared libraries, and core dumps on many Unix-like systems.
- static linker
- A program that combines several object files into a single executable file or another object file. It processes code and data from object files and resolves symbols.
- run-time linker
- A program that is part of the operating system and resolves dynamic library references when an executable is run. Also known as a dynamic linker.