Hi Graeme,
On 21/02/12 10:33, Graeme Russ wrote:
> Hi Alex,
>
> On 02/21/2012 10:45 AM, Alex Hornung wrote:
>> * Adjust the GBL_DATA_OFFSET to account for the fact that we'll be
>> using the space between that offset and the start of the malloc
>> region to allocate both a gd structure and a board info structure.
>>
>> * This fixes a memory corruption bug due to overlap of the malloc
>> region and the bd_info structure.
>>
>> Signed-off-by: Alex Hornung <a...@alexhornung.com>
>> ---
>> include/configs/nios2-generic.h | 3 ++-
>> 1 files changed, 2 insertions(+), 1 deletions(-)
>>
>> diff --git a/include/configs/nios2-generic.h
>> b/include/configs/nios2-generic.h
>> index 9ba35e8..17017a5 100644
>> --- a/include/configs/nios2-generic.h
>> +++ b/include/configs/nios2-generic.h
>> @@ -131,7 +131,8 @@
>> #define CONFIG_SYS_MALLOC_BASE (CONFIG_SYS_MONITOR_BASE - \
>> CONFIG_SYS_MALLOC_LEN)
>> #define CONFIG_SYS_GBL_DATA_OFFSET (CONFIG_SYS_MALLOC_BASE - \
>> - GENERATED_GBL_DATA_SIZE)
>> + GENERATED_GBL_DATA_SIZE - \
>> + GENERATED_BD_INFO_SIZE)
>> #define CONFIG_SYS_INIT_SP CONFIG_SYS_GBL_DATA_OFFSET
>>
>> /*
>
> Oh I really want to NAK this, but I think I might be out-voted
>
> in arch/x86/lib/init_helpers.c I do:
>
> bd_t bd_data;
>
> int init_bd_struct_r(void)
> {
> gd->bd = &bd_data;
> memset(gd->bd, 0, sizeof(bd_t));
>
> return 0;
> }
>
> So the bd struct is in bss
>
> But everyone else (ARM, PPC) seems to do:
>
> addr_sp -= sizeof(bd_t);
> bd = (bd_t *) addr_sp;
>
> Why?
>
> Well I see that a lot of bd is setup while still running from flash, so bss
> is not available. But is this really necessary?
>
> And for the sake of one more copy and pointer adjustment, even gd could be
> moved into bss which would save all the hackish calculations of sticking gd
> and bd in a magic void below the stack
>
> But maybe that's a battle for another day...
To be honest I just started using u-boot, and for that matter, just
started using Nios2. I just ran across the issue and had to fix it to
get u-boot working on my system.
Nonetheless I'd generally agree that less hackery is a better idea, and
putting it in BSS is a good option - but reality is, as you point out,
that most other platforms don't do that, either. For now I think the
above patch should do.
> Oh, and Nios is particularly nasty - It has no init_r / init_f so there is
> no support for relocation - Will there every be an intent to enable
> relocation for Nios or is it pointless?
As I mentioned I'm not really involved with u-boot on Nios, so I can't
answer that question.
Cheers,
Alex
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