PLT Problems in uBoot on MCF548x

[Peter LaDow]

On Tue, Aug 6, 2024 at 1:23 PM Maciej W. Rozycki <macro@orcam.me.uk> wrote:
> [Cc-ed back to the mailing list (I hope you don't mind) as Gmail doesn't
> want to accept e-mail from here and you wouldn't receive it otherwise.
> Also someone else might want to chime in, in particular who knows m68k.]

Doh!  I somehow didn't do reply-all on that last one.  Apologies.

> On Tue, 6 Aug 2024, Peter LaDow wrote:
>  Can you double-check how the definitions of `_fault' and `_start' look
> like?  If you're not sure where they come from after all (which can
> sometimes be confusing), then use the `-M' option to LD to print the link
> map, and it'll tell you the symbol's originating object file or whether
> it's come from a linker script instead.

Linker script and memory map

Address of section .text set to 0x0

.text           0x0000000000000000    0x2c204
arch/m68k/cpu/mcf548x/start.o(.text*)
.text          0x0000000000000000      0x554 arch/m68k/cpu/mcf548x/start.o
               0x0000000000000400                _start
               0x0000000000000474                relocate_code
               0x000000000000050c                _fault
               0x0000000000000510                _exc_handler
               0x0000000000000532                _int_handler
               0x0000000000004000                . = DEFINED (env_offset)?env_o

>  If it came from a piece of handcoded assembly, it would have to have the
> hidden visibility applied also by hand, with the `.hidden _start'
> pseudo-op, typically placed near the symbol definition.  For a linker
> script definition there are the HIDDEN and PROVIDE_HIDDEN commands.

The _start symbol is not mentioned in the linker script, other than an
ENTRY(_start).  I tried removing that, and there's no change in the
output.

>  Then are there no dynamic relocations at all, not even relative ones
> referring no symbol?  If so, then can you run `readelf -r' on the object
> module containing `_vectors' stuff and see what static relocations have
> been produced at assembly time?

There are relocations in start.o (which contains _start, _fault, and
_vectors).  There are R_68K_32 and just a few R_68K_PC16.  I note that
_fault is generated as R_68K_PC16.  But the beginning of the vector
table does show _start (the remainder are _fault):

Relocation section '.rela.text' at offset 0x9e4 contains 271 entries:
Offset     Info    Type            Sym.Value  Sym. Name + Addend
00000004  00000f01 R_68K_32          00000400   _start + 0
00000008  00001001 R_68K_32          0000050c   _fault + 0
...

I'm not sure what you mean by "referring no symbol."  What am I looking for?


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