Friday, June 25, 2010

objdump-ing

So I was trying to figure out which relocation types I really need to worry about when it comes to the GP2x-Wiz today. After making a number of tweaks to the incomplete loader to get it to compile, I compiled and linked (with my modified ARM linker script) the game engines into plugins. I tried using "objdump" on these plugin files to figure out which relocation types were worth my time, but it kept returning all types as "unknown". After a bit of research, I discovered another program "readelf" that successfully dumped relocation types. I noticed, however, that when I do use "objdump -R" which dumps a dynamic relocation table, I get output for both the main "scummvm.wiz" file and the plugin files. This leads me to believe that the binaries may be PIC, but since the version of objdump I'm using doesn't seem to support ARM (as mentioned before, it couldn't detect the relocation types), the reason it's outputting a dynamic relocation table could be because it's misreading the files, not because the files really are PIC. My goal for this weekend, then, is to become more certain about the nature of the generated files, and then to code for the relocations I may need to worry about, which are listed below (the names of some of these relocations also has me worried about PIC code):

  • R_ARM_GLOB_DAT
  • R_ARM_JUMP_SLOT
  • R_ARM_COPY
  • R_ARM_PLT32
  • R_ARM_PC24 
  • R_ARM_BASE_PREL
  • R_ARM_GOT_BREL
  • R_ARM_PC24
  • R_ARM_ABS32

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