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When building PIE (ET_DYN) executables, an additional RELA section is
emitted (in addition to the per-section .rela.text and .rela.data sections)
that is intended to be resolved at runtime by a ET_DYN compatible loader.
At the moment, due to the fact that we don't support GOT based relocations,
this dynamic RELA section only contains relocations that are redundant,
i.e., each R_xxx_RELATIVE relocation it contains duplicates a R_xxx_xx64
relocation appearing in .rela.text or .rela.data, and so we can simply
ignore this section (and we already ignore it in practice due to the fact
that it points to the NULL section, which has the SHF_ALLOC bit cleared).
For example,
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .text PROGBITS 0000000000000240 000000c0
000000000000427c 0000000000000008 AX 0 0 64
[ 2] .rela.text RELA 0000000000000000 00009310
0000000000001bf0 0000000000000018 I 7 1 8
[ 3] .data PROGBITS 00000000000044c0 00004340
00000000000046d0 0000000000000000 WA 0 0 64
[ 4] .rela.data RELA 0000000000000000 0000af00
0000000000000600 0000000000000018 I 7 3 8
[ 5] .rela RELA 0000000000008bc0 00008a10
0000000000000600 0000000000000018 0 0 8
[ 6] .shstrtab STRTAB 0000000000000000 0000b500
0000000000000037 0000000000000000 0 0 1
[ 7] .symtab SYMTAB 0000000000000000 00009010
0000000000000210 0000000000000018 8 17 8
[ 8] .strtab STRTAB 0000000000000000 00009220
00000000000000eb 0000000000000000 0 0 1
Relocation section '.rela.data' at offset 0xaf00 contains 64 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000004800 000100000001 R_X86_64_64 0000000000000240 .text + 3f5b
000000004808 000100000001 R_X86_64_64 0000000000000240 .text + 3f63
000000004810 000100000001 R_X86_64_64 0000000000000240 .text + 3f79
000000004818 000100000001 R_X86_64_64 0000000000000240 .text + 3f90
000000004820 000100000001 R_X86_64_64 0000000000000240 .text + 3fa6
...
Relocation section '.rela' at offset 0x8a10 contains 64 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000004800 000000000008 R_X86_64_RELATIVE 419b
000000004808 000000000008 R_X86_64_RELATIVE 41a3
000000004810 000000000008 R_X86_64_RELATIVE 41b9
000000004818 000000000008 R_X86_64_RELATIVE 41d0
000000004820 000000000008 R_X86_64_RELATIVE 41e6
000000004828 000000000008 R_X86_64_RELATIVE 41ff
...
Note that GOT based relocations result in entries that *only* appear in the
dynamic .rela section and not in .rela.text or .rela.data. This means two
things if we intend to add support for GOT based relocations:
- we must check that a dynamic RELA section exists;
- we must filter out duplicates between .rela and .rela.xxx, to prevent
emitting duplicate fixups into the PE/COFF .reloc section.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>
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|---|---|---|
| .. | ||
| Bin | ||
| BinWrappers/PosixLike | ||
| Conf | ||
| gcc | ||
| Scripts | ||
| Source | ||
| Tests | ||
| UserManuals | ||
| .gitignore | ||
| BuildEnv | ||
| building-gcc.txt | ||
| BuildNotes.txt | ||
| Contributions.txt | ||
| get_vsvars.bat | ||
| GNUmakefile | ||
| License.txt | ||
| Makefile | ||
| ReadMe.txt | ||
| toolsetup.bat | ||
This directory contains the next generation of EDK II build tools and template files. Templates are located in the Conf directory, while the tools executables for Microsoft Windows 32-bit Operating Systems are located in the Bin\Win32 directory, other directory contatins tools source. 1. 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.txt is located.) * PYTHON_FREEZER_PATH - Path to where the python freezer tool is installed 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-get install build-essential uuid-dev === Python sqlite3 module === On Windows, the cx_freeze will not copy the sqlite3.dll to the frozen binary directory (the same directory as build.exe and GenFds.exe). Please copy it manually from <PythonHome>\DLLs. The Python distributed with most recent Linux will have sqlite3 module built in. If not, please install sqlit3 package separately. 26-OCT-2011