Dominique Torette
2014-Jun-24 15:52 UTC
[LLVMdev] Question on ELF relocations and GNU ld compatibility.
Hi, I'm writing a 'LLVM Integrated Assembler' for an in-house 32bits micro controller. As far as now, I've followed the instructions from Simon Cook (Embecosm) as described in http://www.embecosm.com/appnotes/ean10/ean10-howto-llvmas-1.0.html But, I don't catch how to finalize the relocations. In the case of my micro controller, relocation are only used for the 'Jump' instruction. The 'Jump' instruction is composed of 32 bits opcode, followed bit a 32 bits absolute jump address. When parsed, this jump address is saved as an expression. Later, this expression is translated into a fixup. Finally, the fixup is translated into a relocation type by the GetRelocType(). (I only have one relocation type.) The generated ELF file includes the relocation records. I can dump this relocation records with standard linux 'readelf' command. Relocation section '.rela.text' at offset 0x470 contains 2 entries: Offset Info Type Sym.Value Sym. Name + Addend 0000024c 00000101 unrecognized: 1 00000224 Lback + 0 00000254 00000101 unrecognized: 1 00000224 Lback + 0 So far, so good! But the relocation type are unrecognized and the standard linux 'ld' command reports an error. ld: /tmp/branch.o: Relocations in generic ELF (EM: 201) /tmp/branch.o: error adding symbols: File in wrong format My understanding is that now I have to 'open' the GNU 'ld' sources files to add the relocation schema for my 'jump' instruction. I would like to avoid modifying the GNU 'ld' or the LLVM linker. My relocation schema is quite simple: at relocation record offset, I have to write the Sym. Value on 32 bits big endian. Is there such simple relocation schema already built-in the GNU 'ld'? And how to activate it, by returning a relocation type in the GetRelocType()? Thanks, in advance? Dominique Torette. [http://www.spacebel.be/wp-content/uploads/2011/06/image-sign-sbp.jpg] Dominique Torette System Architect Rue des Chasseurs Ardennais - Liège Science Park - B-4031 Angleur Tel: +32 (0) 4 361 81 11 - Fax: +32 (0) 4 361 81 20 www.spacebel.be<http://www.spacebel.be/> ------------------------------------------------------------------------------ E-MAIL DISCLAIMER The present message may contain confidential and/or legally privileged information. If you are not the intended addressee and in case of a transmission error, please notify the sender immediately and destroy this E-mail. Disclosure, reproduction or distribution of this document and its possible attachments is strictly forbidden. SPACEBEL denies all liability for incomplete, improper, inaccurate, intercepted, (partly) destroyed, lost and/or belated transmission of the current information given that unencrypted electronic transmission cannot currently be guaranteed to be secure or error free. Upon request or in conformity with formal, contractual agreements, an originally signed hard copy will be sent to you to confirm the information contained in this E-mail. SPACEBEL denies all liability where E-mail is used for private use. SPACEBEL cannot be held responsible for possible viruses that might corrupt this message and/or your computer system. ------------------------------------------------------------------------------- -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20140624/0f248431/attachment.html>