[U-Boot] Relocation issue - need help!

[Dirk Eibach]

I had exactly the same behaviour some time ago and tracked it down to
this (and posted it on the mailing list, but sadly got no feedback):

In my latest u-boot builds I had some strange behaviour that I finally
tracked down to not fixed up flash addresses in relocated u-boot.
These addresses come from symbols in the .data.rel.ro.local section
that is not handled by u-boot linker scripts at the moment.

Some background on relro: http://www.airs.com/blog/archives/189

Joerg Albert already inquired about this on the gcc ML:
https://gcc.gnu.org/ml/gcc-help/2014-02/msg00017.html and he already
suggested a solution:
https://gcc.gnu.org/ml/gcc-help/2014-02/msg00054.html

So there a three things to notice:
1. Do not use gcc 4.8 and u-boot at the moment.
2. You might not notice that you have a problem until you erase u-boot
from flash (and get your cache flushed).
3. Handling relro properly should be on the TODO-List

Maybe this is already common knowledge an maybe somebody is already
working on this - but I did not notice yet. So in this case: sorry for
the noise :)

2014-10-22 14:39 GMT+02:00 Wolfgang Denk <wd at denx.de>:
> Hi,
>
> I'm trying to track down a "syntax error" issue that gets triggered
> when erasing the U-Boot image in NOR flash.  Symptoms look like this:
>
>         => print update
>         update=protect off 0xfc000000 +${filesize};erase 0xfc000000 +${filesize};cp.b 200000 0xfc000000 ${filesize};protect on 0xfc000000 +${filesize}
>         => run update
>         Un-Protected 2 sectors
>
>         .. done
>         Erased 2 sectors
>         syntax error
>         Protected 2 sectors
>         => run update
>         syntax error
>
> git bisect found commit 199adb6 "common/misc: sparse fixes" as
> culprit; breaking this down further showed a single line in
> common/cli_hush.c to trigger the problem. This patch fixes it:
>
> ---
>  common/cli_hush.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/common/cli_hush.c b/common/cli_hush.c
> index 38da5a0..5bbcfe6 100644
> --- a/common/cli_hush.c
> +++ b/common/cli_hush.c
> @@ -3127,7 +3127,7 @@ static void mapset(const unsigned char *set, int code)
>         for (s=set; *s; s++) map[*s] = code;
>  }
>
> -static void update_ifs_map(void)
> +void update_ifs_map(void)
>  {
>         /* char *ifs and char map[256] are both globals. */
>         ifs = (uchar *)getenv("IFS");
> --
> 1.8.3.1
>
> But I still have bad feelings - symptoms indicate that this is
> actually a relocation issue, as it only gets triggered when erasing
> the U-Boot image in NOR flash, so probably there are still pointers to
> data in NOR being used.  This patch here is not suited to fix the
> original cause of this issue.  But then, I do not see where there
> might be a relocation problem.  To be sure I even verified that "ifs"
> and "map[]" are really in RAM all the time.
>
> Has anybody an idea how to further track this down?  Or is the patch
> above actually a real fix?  If so, why?
>
> Best regards,
>
> Wolfgang Denk
>
> --
> DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
> Old programmers never die, they just branch to a new address.
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