Fix ARM BE8 encoding for SG stubs
Fixes incorrect byte encoding for ARM Secure Gateway stubs in BE8 mode.
This patch corrects the byte encoding for Secure Gateway (SG) stubs in ARM’s Big-Endian 8-bit (BE8) mode within the binutils linker. The issue arises because these veneers are not correctly identified as part of the stub group, preventing the linker from applying the proper BE8 encoding. The fix ensures correct handling for cmse_stub_sec and includes a new test case to verify the raw instruction encoding.
- proposer
Submits a patch to fix incorrect BE8 encoding of ARM SG stubs by ensuring they are processed correctly during the final linking stage.
“This patch adds the same handling for cmse_stub_sec, and a new testcase which checks the raw encoding of the instructions in the veneer.”
In Details
This patch targets the ARM support within the binutils linker (ld), specifically addressing issues with instruction encoding in Big-Endian 8-bit (BE8) mode. The problem lies in how Secure Gateway (SG) stubs, which are part of the CMSE (Code Musing Security Extension) security feature, are handled. Because they were not correctly grouped with other stubs, the linker's final linking pass failed to apply the BE8 encoding transformation to their veneers, resulting in incorrect machine code. The fix involves ensuring these stubs are processed and encoded correctly, with a new test case added for…
- ARM
- A family of reduced instruction set computing (RISC) architectures for processors, widely used in mobile devices and embedded systems.
- BE8 mode
- Big-Endian 8-bit mode, a specific endianness and byte ordering used in ARM architectures, particularly relevant for instruction encoding.
- SG stubs
- Secure Gateway stubs, which are small pieces of code used in ARM's TrustZone or CMSE security extensions to mediate calls between secure and non-secure worlds.
- CMSE
- Code Musing Security Extension, an ARM security feature that provides enhanced protection for software execution environments.
- linker
- A program that combines various object files and libraries into a single executable file or shared library.
- veneer
- In the context of function calls or security mechanisms, a veneer is a small piece of code that acts as an intermediary or wrapper to facilitate the call or enforce security policies.