mirror of https://github.com/acidanthera/audk.git
e07092edca
The self-relocating PrePi module that is used by the ArmVirtQemuKernel and ArmVirtXen targets runs the linker in PIE mode so that it emits dynamic relocations into the final image in a way that permits the module to relocate itself into place before calling into the C code. When building these targets using the CLANG38 toolchain, we switch from the BFD to the GOLD linker, which behaves a bit differently when building PIE executables, and insists on emitting GOT indirected symbol references throughout, which means a) that we end up with absolute addresses (which need to be fixed up at load time) for no good reason, and b) we have to add support for handling GOT entries to GenFw if we want to convert them into PE/COFF. So instead, let's emit a shared library. Since the ELF image only serves as the input to GenFw, this does not lead to any loss of functionality, although it does require the -Bsymbolic linker option to be added to ensure that no symbol based dynamic relocations are emitted (which would, e.g., permit lazy binding for shared libraries). So for all other toolchains, the linker option changes are a no-op. Then, we have to convince CLANG38/GOLD that there is no need to refer to symbols via a GOT entry. This is done by forcing hidden visibility for all symbols in all components that make up the PrePi SEC module: this informs the linker that a symbol is never exported or preempted, making it safe to refer to it directly from anywhere in the code, rather than indirectly via a GOT entry. Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Acked-by: Laszlo Ersek <lersek@redhat.com> |
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