<div dir="ltr">Hi Steven,<div><br></div><div>This is not a direct answer or suggestion for your problem, but why don't you use lld-link (lld for Windows target) instead of ld.lld (lld for Unix target) to create UEFI applications? A quick google search showed me that UEFI applications are in PE/COFF format, and I can even find people who successfully created UEFI applications using lld-link. Looks like that's much more straightforward way than hacking ld.lld with linker scripts.<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Jan 28, 2019 at 7:35 AM Shi, Steven <<a href="mailto:steven.shi@intel.com">steven.shi@intel.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<p class="MsoNormal">Hi Rui,<u></u><u></u></p>
<p class="MsoNormal">I still fail to enable the lld in my Uefi firmware build to replace ld, and I found it is related to the wrong symbol values in the .data section, which are pointed by R_X86_64_64 relocation entries. I need your advices.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">My firmware uses a linker script <a href="https://github.com/tianocore/edk2/blob/master/BaseTools/Scripts/GccBase.lds" target="_blank">
https://github.com/tianocore/edk2/blob/master/BaseTools/Scripts/GccBase.lds</a> to do the linking. We use position independent code with hidden visibility to inform the compiler that symbol references are never resolved at runtime. My problem is I found after
the lld linking with –pie enabled, the symbol values in .data section, which have the R_X86_64_64 relocation entries, are all 0. In other word, I found the S in below R_X86_64_64 calculation is 0.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal"><span style="font-size:9pt;font-family:NimbusRomNo9L-Regu,serif;color:black">Name:</span>
<span style="font-size:9pt;font-family:NimbusMonL-Regu,serif;color:black">R_X86_64_64
</span><span style="font-size:12pt;font-family:"Times New Roman",serif"><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:9pt;font-family:NimbusRomNo9L-Regu,serif;color:black">1
</span><span style="font-size:12pt;font-family:"Times New Roman",serif"><u></u><u></u></span></p>
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<p class="MsoNormal"><i><span style="font-size:9pt;font-family:NimbusRomNo9L-ReguItal,serif;color:black">word64
</span></i><span style="font-size:12pt;font-family:"Times New Roman",serif"><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:9pt;font-family:NimbusMonL-Regu,serif;color:black">S + A</span><span style="font-size:12pt;font-family:"Times New Roman",serif"><u></u><u></u></span></p>
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<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Below is an example to compare the lld and ld, sorry about the verbose.<u></u><u></u></p>
<p class="gmail-m_7943837711040915951MsoListParagraph"><u></u><span>1.<span style="font:7pt "Times New Roman"">
</span></span><u></u>Firstly, I use lld to link a HelloWorld module with -pie enabled:<u></u><u></u></p>
<p class="MsoNormal">"/home/jshi19/llvm/releaseinstall/bin/<span style="color:red">ld.lld</span>"
<span style="color:red">-pie </span>-z relro --hash-style=gnu --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o /home/jshi19/wksp_efi/lgao4/edk2/Build/OvmfX64/NOOPT_CLANG38/X64/MdeModulePkg/Application/HelloWorld/HelloWorld/DEBUG/HelloWorld.dll
-u _ModuleEntryPoint -L/usr/lib/gcc/x86_64-linux-gnu/7.3.0 -L/usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../x86_64-linux-gnu -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../.. -L/home/jshi19/llvm/releaseinstall/bin/../lib
-L/lib -L/usr/lib -q --gc-sections -z max-page-size=0x40 --entry _ModuleEntryPoint -Map /home/jshi19/wksp_efi/lgao4/edk2/Build/OvmfX64/NOOPT_CLANG38/X64/MdeModulePkg/Application/HelloWorld/HelloWorld/DEBUG/HelloWorld.map --whole-archive -O0 -melf_x86_64 --oformat
elf64-x86-64 --start-group @/home/jshi19/wksp_efi/lgao4/edk2/Build/OvmfX64/NOOPT_CLANG38/X64/MdeModulePkg/Application/HelloWorld/HelloWorld/OUTPUT/static_library_files.lst --end-group --defsym=PECOFF_HEADER_SIZE=0x228 --script=/home/jshi19/wksp_efi/lgao4/edk2/BaseTools/Scripts/GccBase.lds<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="gmail-m_7943837711040915951MsoListParagraph"><u></u><span>2.<span style="font:7pt "Times New Roman"">
</span></span><u></u>Then, I check the R_X86_64_64 relocation entries in .rela.data section, and find their target offsets<u></u><u></u></p>
<p class="MsoNormal">$ readelf -r /home/jshi19/wksp_efi/lgao4/edk2/Build/OvmfX64/NOOPT_CLANG38/X64/MdeModulePkg/Application/HelloWorld/HelloWorld/DEBUG/HelloWorld.dll<u></u><u></u></p>
<p class="MsoNormal">Relocation section '.rela.data' at offset 0x5b7e8 contains 41 entries:<u></u><u></u></p>
<p class="MsoNormal"> Offset Info Type Sym. Value Sym. Name + Addend<u></u><u></u></p>
<p class="MsoNormal">… …<u></u><u></u></p>
<p class="MsoNormal"><span style="color:red">000000005040 </span>00d600000001 R_X86_64_64 0000000000003130 TestFunction1 + 0<u></u><u></u></p>
<p class="MsoNormal"><span style="color:red">000000005048 </span>00d700000001 R_X86_64_64 0000000000003150 TestFunction2 + 0<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="gmail-m_7943837711040915951MsoListParagraph"><u></u><span>3.<span style="font:7pt "Times New Roman"">
</span></span><u></u>Next, I check the symbol values in .data section which are targeted by above R_X86_64_64 relocatons<u></u><u></u></p>
<p class="MsoNormal">$ readelf -x2 HelloWorld.dll <u></u><u></u></p>
<p class="MsoNormal">Hex dump of section '.data':<u></u><u></u></p>
<p class="MsoNormal">NOTE: This section has relocations against it, but these have NOT been applied to this dump.<u></u><u></u></p>
<p class="MsoNormal">… …<u></u><u></u></p>
<p class="MsoNormal"> 0x00005030 00000000 00000000 00000000 00000000 ................<u></u><u></u></p>
<p class="MsoNormal"> <span style="color:red">0x00005040 00000000 00000000 00000000 00000000
</span>................<u></u><u></u></p>
<p class="MsoNormal"> 0x00005050 4ebe7903 06d77d43 b037edb8 2fb772a4 N.y...}C.7../.r.<u></u><u></u></p>
<p class="MsoNormal"> 0x00005060 00000000 00000000 00000000 00000000 ................<u></u><u></u></p>
<p class="MsoNormal">… …<u></u><u></u></p>
<p class="MsoNormal">You can see the offset 0x5040 and 0x5048 symbol value are all 0, which is not correct.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">But if I remove the -pie option in the above step 1 lld link command, the 0x5040 and 0x5048 symbol values are correct.<u></u><u></u></p>
<p class="MsoNormal">$ readelf -x2 HelloWorld.dll <u></u><u></u></p>
<p class="MsoNormal">Hex dump of section '.data':<u></u><u></u></p>
<p class="MsoNormal">NOTE: This section has relocations against it, but these have NOT been applied to this dump.<u></u><u></u></p>
<p class="MsoNormal">… …<u></u><u></u></p>
<p class="MsoNormal"> 0x00005030 04420000 00000000 00000000 00000000 .B..............<u></u><u></u></p>
<p class="MsoNormal"><span style="color:red"> 0x00005040 30310000 00000000 50310000 00000000 01......P1......<u></u><u></u></span></p>
<p class="MsoNormal"> 0x00005050 4ebe7903 06d77d43 b037edb8 2fb772a4 N.y...}C.7../.r.<u></u><u></u></p>
<p class="MsoNormal"> 0x00005060 00000000 00000000 00000000 00000000 ................<u></u><u></u></p>
<p class="MsoNormal">… …<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">And if I replace lld with ld but still use exact same link options with –pie enabled, the R_X86_64_64 symbol values are correct.<u></u><u></u></p>
<p class="gmail-m_7943837711040915951MsoListParagraph"><u></u><span>1.<span style="font:7pt "Times New Roman"">
</span></span><u></u>Link again with ld and same link options:<u></u><u></u></p>
<p class="MsoNormal"><span style="color:red">ld -pie </span>-z relro --hash-style=gnu --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o /home/jshi19/wksp_efi/lgao4/edk2/Build/OvmfX64/NOOPT_CLANG38/X64/MdeModulePkg/Application/HelloWorld/HelloWorld/DEBUG/HelloWorld.dll
-u _ModuleEntryPoint -L/usr/lib/gcc/x86_64-linux-gnu/7.3.0 -L/usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../x86_64-linux-gnu -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../.. -L/home/jshi19/llvm/releaseinstall/bin/../lib
-L/lib -L/usr/lib -q --gc-sections -z max-page-size=0x40 --entry _ModuleEntryPoint -Map /home/jshi19/wksp_efi/lgao4/edk2/Build/OvmfX64/NOOPT_CLANG38/X64/MdeModulePkg/Application/HelloWorld/HelloWorld/DEBUG/HelloWorld.map --whole-archive -O0 -melf_x86_64 --oformat
elf64-x86-64 --start-group @/home/jshi19/wksp_efi/lgao4/edk2/Build/OvmfX64/NOOPT_CLANG38/X64/MdeModulePkg/Application/HelloWorld/HelloWorld/OUTPUT/static_library_files.lst --end-group --defsym=PECOFF_HEADER_SIZE=0x228 --script=/home/jshi19/wksp_efi/lgao4/edk2/BaseTools/Scripts/GccBase.lds<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="gmail-m_7943837711040915951MsoListParagraph"><u></u><span>2.<span style="font:7pt "Times New Roman"">
</span></span><u></u>Then, check the .rela.data section R_X86_64_64 relocation entries:<u></u><u></u></p>
<p class="MsoNormal">… …<u></u><u></u></p>
<p class="MsoNormal"><span style="color:red">000000004f40 </span>00a400000001 R_X86_64_64 0000000000003130 TestFunction1 + 0<u></u><u></u></p>
<p class="MsoNormal"><span style="color:red">000000004f48 </span>009a00000001 R_X86_64_64 0000000000003150 TestFunction2 + 0<u></u><u></u></p>
<p class="MsoNormal">… …<u></u><u></u></p>
<p class="gmail-m_7943837711040915951MsoListParagraph"><u></u><span>3.<span style="font:7pt "Times New Roman"">
</span></span><u></u>Check the R_X86_64_64 targeting symbol values in .data section<u></u><u></u></p>
<p class="MsoNormal">… …<u></u><u></u></p>
<p class="MsoNormal"> 0x00004f30 f3410000 00000000 00000000 00000000 .A..............<u></u><u></u></p>
<p class="MsoNormal"> <span style="color:red">0x00004f40 30310000 00000000 50310000 00000000 01......P1......</span><u></u><u></u></p>
<p class="MsoNormal"> 0x00004f50 00000000 00000000 00000000 00000000 ................<u></u><u></u></p>
<p class="MsoNormal">… …<u></u><u></u></p>
<p class="MsoNormal">You can see the offset 0x4f40 and 0x4f48 symbol value are not 0, which is correct.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Appreciate if you could give me some advices on how to let lld output correct symbol values when enable pie.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Thanks<u></u><u></u></p>
<p class="MsoNormal">Steven<b><span style="font-size:12pt;font-family:Arial,sans-serif"><u></u><u></u></span></b></p>
<p class="MsoNormal"><u></u> <u></u></p>
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</blockquote></div>