[U-Boot] [PATCH RFC 3/3] arm920t: do not relocate NULL pointer

[Andreas Bießmann]

Dear Joakim Tjernlund,
Dear Albert ARIBAUD,

Am 30.11.2010 10:41, schrieb Joakim Tjernlund:
> Albert ARIBAUD <albert at aribaud.net> wrote on 2010/11/30 10:02:45:
>>
>> Le 30/11/2010 09:47, Joakim Tjernlund a écrit :
>>>>
>>>> Le 30/11/2010 08:06, Andreas Bießmann a écrit :
>>>>> Signed-off-by: Andreas Bießmann<andreas.devel at googlemail.com>
>>>>
>>>>> +   cmp   r1, #0         /* symbol == NULL ? */
>>>>> +   beq   fixnext
>>>>
>>>> Nak. Don't hide a null pointer. NULL pointers are *not* relocated, since
>>>> they are a constant. If a NULL ends up in relocation tables, that is
>>>> because of a corruption *or* because it was to be relocated, and should
>>>> thus never be ignored.
>>>
>>> Depends, if the same routine is used for relocating fixups you need
>>> this test. Undefined weaks will generate a NULL fixup entry.
>>
>> Understood.
> 
> note that I don't know how this routine is used so if just
> relocates the GOT you don't need to test for NULL.
> 
>>
>> Weren't there an effort to not use weak symbols any more?
> 
> ehh, not what I am aware of. Just that we should not use(ATM)
> undefined weaks.

Ok, I did forget to investigate that as mentioned in
http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/88024/focus=88324

Here are the results:

Currently arm920/at91 devices have one undefined weak symbol in .dynsym:

---8<---
Symbol table '.dynsym' contains 11 entries:
   Num:    Value  Size Type    Bind   Vis      Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND <corrupt>
     1: 10000000     0 SECTION LOCAL  DEFAULT    1 <corrupt>
     2: 10028a28     0 SECTION LOCAL  DEFAULT    6 <corrupt>
     3: 10029ff8     0 NOTYPE  GLOBAL DEFAULT    9 <corrupt>
     4: 100299f4     0 NOTYPE  GLOBAL DEFAULT  ABS <corrupt>
     5: 00000000     0 NOTYPE  WEAK   DEFAULT  UND <corrupt>
     6: 10029ff8     0 NOTYPE  GLOBAL DEFAULT  ABS <corrupt>
     7: 10029ff8     0 NOTYPE  GLOBAL DEFAULT   11 <corrupt>
     8: 1002edf0     0 NOTYPE  GLOBAL DEFAULT   10 <corrupt>
     9: 100701c0     0 NOTYPE  GLOBAL DEFAULT   11 <corrupt>
    10: 1002edf0     0 NOTYPE  GLOBAL DEFAULT    9 <corrupt>
--->8---

---8<---
Hex dump of section '.dynsym':
  0x1002edf0 00000000 00000000 00000000 00000000 ................
  0x1002ee00 00000000 00000010 00000000 03000100 ................
  0x1002ee10 00000000 288a0210 00000000 03000600 ....(...........
  0x1002ee20 25000000 f89f0210 00000000 10000900 %...............
  0x1002ee30 01000000 f4990210 00000000 1000f1ff ................
  0x1002ee40 5e000000 00000000 00000000 20000000 ^........... ...
  0x1002ee50 14000000 f89f0210 00000000 1000f1ff ................
  0x1002ee60 52000000 f89f0210 00000000 10000b00 R...............
  0x1002ee70 43000000 f0ed0210 00000000 10000a00 C...............
  0x1002ee80 20000000 c0010710 00000000 10000b00  ...............
  0x1002ee90 35000000 f0ed0210 00000000 10000900 5...............
--->8---

So there are two options here.

First is to apply '[PATCH v2 1/2] arm920t/at91/reset.c: fix weak
reset_board()' second (and safer) is to apply (maybe modified) '[PATCH
RFC 3/3] arm920t: do not relocate NULL pointer'.

which one is preferred? Or should we do both?

regards

Andreas Bießmann