[U-Boot] [PATCH v6 03/13] efi: sandbox: Adjust memory usage for sandbox

[Alexander Graf]

> Am 14.06.2018 um 16:12 schrieb Simon Glass <sjg at chromium.org>:
> 
> Hi Alex,
> 
>> On 14 June 2018 at 07:41, Alexander Graf <agraf at suse.de> wrote:
>>> On 06/14/2018 02:58 PM, Simon Glass wrote:
>>> 
>>> Hi Alex,
>>> 
>>>> On 14 June 2018 at 04:12, Alexander Graf <agraf at suse.de> wrote:
>>>> 
>>>>> On 06/13/2018 04:37 AM, Simon Glass wrote:
>>>>> 
>>>>> With sandbox the U-Boot code is not mapped into the sandbox memory range
>>>>> so does not need to be excluded when allocating EFI memory. Update the
>>>>> EFI
>>>>> memory init code to take account of that.
>>>>> 
>>>>> Also use mapmem instead of a cast to convert a memory address to a
>>>>> pointer.
>>>>> 
>>>>> Signed-off-by: Simon Glass <sjg at chromium.org>
>>>>> ---
>>>>> 
>>>>> Changes in v6: None
>>>>> Changes in v5: None
>>>>> Changes in v4: None
>>>>> Changes in v3: None
>>>>> Changes in v2:
>>>>> - Update to use mapmem instead of a cast
>>>>> 
>>>>>   lib/efi_loader/efi_memory.c | 31 ++++++++++++++++++-------------
>>>>>   1 file changed, 18 insertions(+), 13 deletions(-)
>>>>> 
>>>>> diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
>>>>> index ec66af98ea..210e49ee8b 100644
>>>>> --- a/lib/efi_loader/efi_memory.c
>>>>> +++ b/lib/efi_loader/efi_memory.c
>>>>> @@ -9,6 +9,7 @@
>>>>>   #include <efi_loader.h>
>>>>>   #include <inttypes.h>
>>>>>   #include <malloc.h>
>>>>> +#include <mapmem.h>
>>>>>   #include <watchdog.h>
>>>>>   #include <linux/list_sort.h>
>>>>>   @@ -393,7 +394,7 @@ efi_status_t efi_allocate_pool(int pool_type,
>>>>> efi_uintn_t size, void **buffer)
>>>>>                                &t);
>>>>>         if (r == EFI_SUCCESS) {
>>>>> -               struct efi_pool_allocation *alloc = (void
>>>>> *)(uintptr_t)t;
>>>>> +               struct efi_pool_allocation *alloc = map_sysmem(t, size);
>>>> 
>>>> 
>>>> This is still the wrong spot. We don't want the conversion to happen when
>>>> going from an EFI internal address to an allocation, but when determining
>>>> which addresses are usable in the first place.
>>> 
>>> There seem to be two ways to do this:
>>> 
>>> 1. Record addresses (ulong) in the EFI tables and use map_sysmem()
>>> before returning an address in the allocator
>>> 2. Store pointers in the EFI tables using map_sysmem(), then do no
>>> mapping in the allocator
>>> 
>>> I've gone with option 1 since:
>>> 
>>> - the EFI addresses are not pointers
>>> - it makes sandbox consistent with other architectures which use an
>>> address rather than a pointer in EFI tables
>>> - we don't normally do pointer arithmetic on the results of map_sysmem()
>>> - we normally map the memory when it is used rather than when it is set up
>>> 
>>> I think you are asking for option 2. I think that would get very
>>> confusing. The addresses where things actually end up in sandbox are
>>> best kept to sandbox.
>>> 
>>> Overall I feel that you are either missing the point of sandbox
>>> addressing, or don't agree with how it is done. But it does work
>>> pretty well and we don't get a lot of confusion with sandbox pointers
>>> since we typically use the address until the last moment.
>> 
>> 
>> I've assembled a quick tree for version 2. With that I'm able to run a
>> simple hello world efi application. Grub refuses to start because it wants
>> memory in the low 32bit and also emits random PIO accessing functions, which
>> obviously don't work work from user space.
>> 
>> But overall, I think this is the right path to tackle this:
>> 
>>  https://github.com/agraf/u-boot/tree/efi-sandbox
> 
> What do you mean by version 2?

Option 2 is what you called it. It's the only option we have to make efi binaries work.

> It looks like you've added one patch,
> so will you send that to the list?

It's more than 1 patch. And yes, I'll send them.

> 
> Anyway, I hope I can convince you of the above, the way sandbox memory works.

I still dislike option 1 :)

The reason is simple: The efi memory map is available to efi payloads. It's perfectly legal for them to do a static allocation at a particular address. We also share a lot of (host) pointers for callbacks and structs already with efi applications, so there is no real point to have a split brain situation between u-boot and host pointers.


Alex