M68K Vectors
Peter LaDow
pladow at gmail.com
Fri Jul 26 22:16:13 CEST 2024
I should mention I was using the gcc-m68k-linux-gnu package on Ubuntu
22.04.4, which pulled in gcc-11-m68k-linux-gnu.
I just downloaded the bootlin m68k-coldfire--uclibc--stable-2024.02-1,
and tried that. It generates the proper value in the vector table
(0x400 for _start). But the call to memset is still bad:
0000f5da <board_init_f_init_reserve>:
f5da: 2f02 movel %d2,%sp at -
f5dc: 242f 0008 movel %sp@(8),%d2
f5e0: 4878 00c0 pea c0 <_vectors+0xc0>
f5e4: 42a7 clrl %sp at -
f5e6: 2f02 movel %d2,%sp at -
f5e8: 61ff 0001 4622 bsrl 23c0c <_etext+0x138>
f5ee: 2f02 movel %d2,%sp at -
f5f0: 61ff ffff ffd2 bsrl f5c4 <arch_setup_gd>
f5f6: 0682 0000 00c0 addil #192,%d2
f5fc: 4fef 0010 lea %sp@(16),%sp
f600: 2047 moveal %d7,%a0
f602: 2142 00a0 movel %d2,%a0@(160)
f606: 241f movel %sp at +,%d2
f608: 4e75 rts
Note "bsrl 23c0c" which points beyond _etext.
On Fri, Jul 26, 2024 at 12:59 PM Fabio Estevam <festevam at gmail.com> wrote:
>
> 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.
--
To love for the sake of being loved is human, but to love for the sake
of loving is angelic. -- Alphonse de Lamartine.
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