[U-Boot-Users] Changing u-boot relocation scheme

[Haavard Skinnemoen <haavard.skinnemoen@atmel.com>]

On Fri, 25 Jul 2008 19:28:48 +0200
kenneth johansson <kenneth@southpole.se> wrote:

> I was afraid that what was needed was more or less a complete linker but
> it looks like if one generate the dynamic reloc table a much simpler
> linker(relocation function) is needed. Still probably a lot more complex
> than the GOT and fixup code that is just a loop over a table. We may
> need a case also ;-) 

Hmm...looks like linking with -pie (or --pic-executable) does
something vaguely resembling the trick. But I don't know what vintage
of ld you need for this to be available and actually work...

hskinnemoen at siona:~/work/u-boot/master$ avr32-linux-readelf -d u-boot

Dynamic section at offset 0x1b8f0 contains 12 entries:
  Tag        Type                         Name/Value
 0x00000004 (HASH)                       0x182ac
 0x00000005 (STRTAB)                     0x18260
 0x00000006 (SYMTAB)                     0x18150
 0x0000000a (STRSZ)                      74 (bytes)
 0x0000000b (SYMENT)                     16 (bytes)
 0x00000003 (PLTGOT)                     0x1ae70
 0x70000001 (Processor Specific: 70000001) 0xe6c
 0x00000015 (DEBUG)                      0x0
 0x00000007 (RELA)                       0x1833c
 0x00000008 (RELASZ)                     6996 (bytes)
 0x00000009 (RELAENT)                    12 (bytes)
 0x00000000 (NULL)                       0x0

The dynamic relocation section became surprisingly large. I wonder if
we actually manage to manually relocate all those buggers...I checked a
couple of them and in both cases it looked like something that needed
to be relocated, but I couldn't find any code that actually did it.

One example from common/cmd_itest.c:

op_tbl_t op_table [] = {
        { "-lt", LT },
        { "<"  , LT },
        { "-gt", GT },
        { ">"  , GT },
        { "-eq", EQ },
        { "==" , EQ },
        { "-ne", NE },
        { "!=" , NE },
        { "<>" , NE },
        { "-ge", GE },
        { ">=" , GE },
        { "-le", LE },
        { "<=" , LE },
};

Does this really work without any relocation? Or is it being relocated
and I'm just too blind to see it?

The symbol tables can probably be made smaller with some careful
ldscript tweaking.

Haavard