mirror of https://github.com/acidanthera/audk.git
7b8f69d7e1
Rebecca reports that builds of AArch64 DSCs that involve PIE linking when using ELF based toolchains are failing in some cases, resulting in an error message like bad definition for symbol '_GLOBAL_OFFSET_TABLE_'@0x72d8 or unsupported symbol type. For example, absolute and undefined symbols are not supported. The reason turns out to be that, while GenFw does carry some logic to convert GOT based symbol references into direct ones (which is always possible given that our ELF to PE/COFF conversion only supports fully linked executables), it does not support all possible combinations of relocations that the linker may emit to load symbol addresses from the GOT. In particular, when performing a non-LTO link on object code built with GCC using -fpie, we may end up with GOT based references such as the one below, where the address of the GOT itself is taken, and the offset of the symbol in the GOT is reflected in the immediate offset of the subsequent LDR instruction. 838: adrp x0, 16000 838: R_AARCH64_ADR_PREL_PG_HI21 _GLOBAL_OFFSET_TABLE_ 83c: ldr x0, [x0, #2536] 83c: R_AARCH64_LD64_GOTPAGE_LO15 _gPcd_BinaryPatch_PcdFdBaseAddress The reason that we omit GOT based symbol references when performing ELF to PE/COFF conversion is that the GOT is not described by static ELF relocations, which means that the ELF file lacks the metadata to generate the PE/COFF relocations covering the GOT table in the PE/COFF executable. Given that none of the usual motivations for using a GOT (copy on write footprint, shared libraries) apply to EFI executables in the first place, the easiest way around this is to convert all GOT based symbol address loads to PC relative ADR/ADRP instructions. So implement this handling for R_AARCH64_LD64_GOTPAGE_LO15 and R_AARCH64_LD64_GOTOFF_LO15 relocations as well, and turn the LDR instructions in question into ADR instructions that generate the address immediately. This leaves the reference to _GLOBAL_OFFSET_TABLE_ itself, which is what generated the error to begin with. Considering that this symbol is never referenced (i.e., it doesn't appear anywhere in the code) and is only meaningful in combination with R_*_GOT_* based relocations that follow it, we can just disregard any references to it entirely, given that we convert all of those followup relocations into direct references. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Tested-by: Rebecca Cran <rebecca@bsdio.com> Acked-by: Leif Lindholm <quic_llindhol@quicinc.com> Acked-by: Bob Feng <bob.c.feng@intel.com> |
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| .. | ||
| Bin | ||
| BinPipWrappers | ||
| BinWrappers | ||
| Conf | ||
| Plugin | ||
| Scripts | ||
| Source | ||
| Tests | ||
| UserManuals | ||
| .gitignore | ||
| BuildEnv | ||
| Edk2ToolsBuild.py | ||
| GNUmakefile | ||
| Makefile | ||
| ReadMe.rst | ||
| basetools_calling_path_env.yaml | ||
| basetools_path_env.yaml | ||
| get_vsvars.bat | ||
| set_vsprefix_envs.bat | ||
| toolsetup.bat | ||
ReadMe.rst
This directory contains the EDK II build tools and template files. Templates are located in the Conf directory, while the tools executables for Microsoft Windows Operating Systems are located in the Bin\\Win32 directory, other directory contains tools source. Build step to generate the binary tools --------------------------------------- Windows/Visual Studio Notes =========================== To build the BaseTools, you should run the standard vsvars32.bat script from your preferred Visual Studio installation or you can run get_vsvars.bat to use latest automatically detected version. In addition to this, you should set the following environment variables:: * EDK_TOOLS_PATH - Path to the BaseTools sub directory under the edk2 tree * BASE_TOOLS_PATH - The directory where the BaseTools source is located. (It is the same directory where this README.rst is located.) After this, you can run the toolsetup.bat file, which is in the same directory as this file. It should setup the remainder of the environment, and build the tools if necessary. Please also refer to the ``BuildNotes.txt`` file for more information on building under Windows. Unix-like operating systems =========================== To build on Unix-like operating systems, you only need to type ``make`` in the base directory of the project. Ubuntu Notes ============ On Ubuntu, the following command should install all the necessary build packages to build all the C BaseTools:: sudo apt install build-essential uuid-dev