[U-Boot] [PATCH 13/57] x86: Move new_gd_addr to arch_global_data

[Simon Glass]

Hi Graeme,

On Sat, Nov 17, 2012 at 5:07 PM, Graeme Russ <graeme.russ at gmail.com> wrote:
> Hi Simon,
>
> On 11/17/2012 08:19 AM, Simon Glass wrote:
>> Move this field into arch_global_data and tidy up.
>>
>> This will certainly break x86, so will need Graeme's help to sort out
>
> Yes, it most certainly will break x86 :)
>
>> the problem. I would prefer not to put the architecture-specific stuff
>> at the top of global_data since we relying on that seems even more ugly.
>
> The fix is not that hard though...
>
> The whole point of putting gdt_addr at the top of the global data structure
> is to guarantee that is is the very fist void * in gd. The trick is how we
> use the 'F' segment. By loading the fs register with the physical address
> of gd, virtual address 0 of fs contains the address of gd.
>
> But really, we can put the address of gd anywhere, as long as we set fs to
> be that address
>
>>
>> Signed-off-by: Simon Glass <sjg at chromium.org>
>> ---
>>  arch/x86/cpu/cpu.c                 |    2 +-
>>  arch/x86/include/asm/global_data.h |   12 +++++++++---
>>  arch/x86/lib/init_helpers.c        |    2 +-
>>  3 files changed, 11 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/cpu/cpu.c b/arch/x86/cpu/cpu.c
>> index e9bb0d7..c276aa6 100644
>> --- a/arch/x86/cpu/cpu.c
>> +++ b/arch/x86/cpu/cpu.c
>> @@ -92,7 +92,7 @@ static void load_gdt(const u64 *boot_gdt, u16 num_entries)
>>
>>  void init_gd(gd_t *id, u64 *gdt_addr)
>>  {
>> -     id->gd_addr = (ulong)id;
>> +     id->arch.gd_addr = (ulong)id;
>>       setup_gdt(id, gdt_addr);
>
> If the original code had been:
>
> setup_gdt(&(id->gd_addr), gdt_addr);
>
> There would have been no reliance on gd_addr being the first member of gd.
> So change this to:
>
> setup_gdt(&(id->arch.gd_addr), gdt_addr);
>
> And you should be pretty much set - and gd_addr can be anywhere in the arch gd.

Thanks for that. I actually understand it now, for better or worse. It
seems to work fine. Actually your clean-up of the global_data really
has paid dividends as things are so much nicer now.

I'm going to resend the whole series rebased to master.

Regards,
Simon

>
>>  }
>>
>> diff --git a/arch/x86/include/asm/global_data.h b/arch/x86/include/asm/global_data.h
>> index 3df83bb..d2eb00a 100644
>> --- a/arch/x86/include/asm/global_data.h
>> +++ b/arch/x86/include/asm/global_data.h
>> @@ -28,8 +28,16 @@
>>
>>  /* Architecture-specific global data */
>>  struct arch_global_data {
>> -     unsigned long gdt_addr;         /* Location of GDT */
>> +     /*
>> +      * NOTE: gd_addr MUST be first member of struct global_data!
>> +      *
>> +      * But it now isn't, so this is sure to break x86. Can we change
>> +      * x86 to not require this? I don't think we should put the
>> +      * arch data first in global_data...
>> +      */
>
> Yes we can - see above
>
>>       unsigned long new_gd_addr;      /* New location of Global Data */
>> +     unsigned long gd_addr;          /* Location of Global Data */
>> +     unsigned long gdt_addr;         /* Location of GDT */
>>  };
>>
>>  /*
>> @@ -41,8 +49,6 @@ struct arch_global_data {
>>   */
>>
>>  typedef      struct global_data {
>> -     /* NOTE: gd_addr MUST be first member of struct global_data! */
>> -     unsigned long   gd_addr;        /* Location of Global Data */
>>       bd_t            *bd;
>>       unsigned long   flags;
>>       unsigned int    baudrate;
>> diff --git a/arch/x86/lib/init_helpers.c b/arch/x86/lib/init_helpers.c
>> index 05cadcd..ac789c2 100644
>> --- a/arch/x86/lib/init_helpers.c
>> +++ b/arch/x86/lib/init_helpers.c
>> @@ -126,7 +126,7 @@ int copy_gd_to_ram_f_r(void)
>>        * in-RAM copy of Global Data (calculate_relocation_address()
>>        * has already calculated the in-RAM location of the GDT)
>>        */
>> -     ram_gd->gd_addr = (ulong)ram_gd;
>> +     ram_gd->arch.gd_addr = (ulong)ram_gd;
>>       init_gd(ram_gd, (u64 *)gd->arch.gdt_addr);
>>
>>       return 0;
>>
>
> Regards,
>
> Graeme