M68K Vectors

[Fabio Estevam]

Adding the Coldfire maintainers on Cc.

On Fri, Jul 26, 2024 at 4:46 PM Peter LaDow <pladow at gmail.com> wrote:
>
> After some digging it appears that this is a toolchain issue.  It seems the
> linker fixups are sometimes not computed correctly.  For example, in
> board_init_f_init_reserve, the object file disassembled has:
>
> 00000000 <board_init_f_init_reserve>:
>   0:   2f02            movel %d2,%sp at -
>   2:   242f 0008       movel %sp@(8),%d2
>   6:   4878 00c0       pea c0 <board_init_f_init_reserve+0xc0>
>   a:   42a7            clrl %sp at -
>   c:   2f02            movel %d2,%sp at -
>   e:   61ff 0000 0000  bsrl 10 <board_init_f_init_reserve+0x10>
>  14:   2f02            movel %d2,%sp at -
>  16:   61ff 0000 0000  bsrl 18 <board_init_f_init_reserve+0x18>
>  1c:   0682 0000 00c0  addil #192,%d2
>  22:   4fef 0010       lea %sp@(16),%sp
>  26:   2047            moveal %d7,%a0
>  28:   2142 00a0       movel %d2,%a0@(160)
>  2c:   241f            movel %sp at +,%d2
>  2e:   4e75            rts
>
> But when I disassemble the final linked u-boot output:
>
> 0000f646 <board_init_f_init_reserve>:
>    f646:       2f02            movel %d2,%sp at -
>    f648:       242f 0008       movel %sp@(8),%d2
>    f64c:       4878 00c0       pea c0 <_vectors+0xc0>
>    f650:       42a7            clrl %sp at -
>    f652:       2f02            movel %d2,%sp at -
>    f654:       61ff 0001 44da  bsrl 23b30 <_etext+0x138>
>    f65a:       2f02            movel %d2,%sp at -
>    f65c:       61ff ffff ffd2  bsrl f630 <arch_setup_gd>
>    f662:       0682 0000 00c0  addil #192,%d2
>    f668:       4fef 0010       lea %sp@(16),%sp
>    f66c:       2047            moveal %d7,%a0
>    f66e:       2142 00a0       movel %d2,%a0@(160)
>    f672:       241f            movel %sp at +,%d2
>    f674:       4e75            rts
>
> Note the pea c0 instruction.  The object file has
> board_init_f_init_reserve+0xc0 as the argument, but the final linker has
> 0xc0, meaning board_init_f_init_reserve is being set to 0 after linking.
>
> Also, note the first bsrl instruction, which is not setup correctly
> either.  This is a call to memset.  This points to _etext+0x138, which is
> not a code region Note that 0x239f8 + 0x138 = 0x23b30.  But in the final
> uboot, memset is at 0x1f030.
>
> In the call to memset(),  objdump shows the relocation:
>
> RELOCATION RECORDS FOR [.text.board_init_f_init_reserve]:
> OFFSET   TYPE              VALUE
> 00000010 R_68K_PLT32       memset
> 00000018 R_68K_PLT32       arch_setup_gd
>
> So it seems only when linking outside the same compilation unit that the
> relocations aren't set correctly.
>
> I'm not sure where to look for a solution.  Or how to search for an
> answer.  I've done some digging on Google, but nothing points to a clear
> answer.  Anyone seen something similar?
>
> To love for the sake of being loved is human, but to love for the sake of
> loving is angelic. -- Alphonse de Lamartine.
>
>
> On Thu, Jul 25, 2024 at 14:35 Peter LaDow <pladow at gmail.com> wrote:
> >
> > I'm trying to add support for a custom Colfire based board.  I have
> > things building, but the final linked vectors in start.S do not point
> > to _start.  In start.S I have:
> >
> > _vectors:
> > .long   0x00000000              /* Flash offset is 0 until we setup CS0 */
> > .long   _START
> >
> > .long   _FAULT, _FAULT, _FAULT, _FAULT, _FAULT, _FAULT, _FAULT, _FAULT
> > .long   _FAULT, _FAULT, _FAULT, _FAULT, _FAULT, _FAULT, _FAULT, _FAULT
> > .long   _FAULT, _FAULT, _FAULT, _FAULT, _FAULT, _FAULT, _FAULT, _FAULT
> >
> > Dumping the symbols in the final u-boot yields:
> >
> > $ m68k-linux-gnu-nm -n u-boot
> > 00000000 A __fixup_entries
> > 00000000 A __got2_entries
> > 00000000 t _vectors
> > 00000400 T _start
> > 0000047e T relocate_code
> > 000004ae t fixloop
> >
> > But then dumping the raw binary:
> >
> > u-boot:     file format elf32-m68k
> >
> > Contents of section .text:
> > 00000 00000000 00000000 00000516 00000516  ................
> > 00010 00000516 00000516 00000516 00000516  ................
> > 00020 00000516 00000516 00000516 00000516  ................
> > 00030 00000516 00000516 00000516 00000516  ................
> >
> > Note at offset 4 it is 0x00000000, not 0x00000400 as I'd expect.
> >
> > The final linker script has:
> >
> > OUTPUT_ARCH(m68k)
> > ENTRY(_start)
> > SECTIONS
> > {
> > .text :
> > {
> >  arch/m68k/cpu/mcf548x/start.o (.text*)
> >  . = DEFINED(env_offset) ? env_offset : .; env/embedded.o(.text*);
> >  *(.text*)
> > }
> >
> >
> > It is difficult to search the archives, and so far I haven't found
> > anything.  Any help would be appreciated.
> >
> > --
> > To love for the sake of being loved is human, but to love for the sake
> > of loving is angelic. -- Alphonse de Lamartine.