[U-Boot] [PATCH v6 03/13] efi: sandbox: Adjust memory usage for sandbox
Alexander Graf
agraf at suse.de
Thu Jun 14 16:26:04 UTC 2018
On 06/14/2018 06:13 PM, Simon Glass wrote:
> Hi Alex,
>
> On 14 June 2018 at 10:07, Alexander Graf <agraf at suse.de> wrote:
>> On 06/14/2018 05:53 PM, Simon Glass wrote:
>>> Hi Alex,
>>>
>>> On 14 June 2018 at 09:47, Alexander Graf <agraf at suse.de> wrote:
>>>>
>>>>> Am 14.06.2018 um 17:43 schrieb Simon Glass <sjg at chromium.org>:
>>>>>
>>>>> Hi Alex,
>>>>>
>>>>>> On 14 June 2018 at 08:22, Alexander Graf <agraf at suse.de> wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>> 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.
>>>>> OK so you mean they don't have to allocate memory before using it? How
>>>>> then do you make sure that there is no conflict? I thought EFI was an
>>>>> API?
>>>> You allocate it, but payloads expect that the address you pass in as
>>>> address you allocate at is the pointer/address that gets returned.
>>>>
>>> Can you please point me to that? Are you referring to this call?
>>>
>>> static efi_status_t EFIAPI efi_get_memory_map_ext(
>>> efi_uintn_t *memory_map_size,
>>> struct efi_mem_desc *memory_map,
>>> efi_uintn_t *map_key,
>>> efi_uintn_t *descriptor_size,
>>> uint32_t *descriptor_version)
>>>
>>> If so, we can still support that.
>>>
>>>> In a nutshell, what you're proposing is that the efi quivalent of
>>>> mmap(addr, MAP_FIXED) returns something != addr. That will break things.
>>> I see this function:
>>>
>>> efi_status_t efi_allocate_pool(int pool_type, efi_uintn_t size, void
>>> **buffer)
>>>
>>> So there appears to be no way for people to specify the address they
>>> want. Is there another call somewhere?
>>
>> You can call efi_allocate_pages() with EFI_ALLOCATE_ADDRESS or even
>> EFI_ALLOCATE_MAX_ADDRESS which you usually base on information you receive
>> from efi_get_memory_map().
> That's fine though, I'm not worried about that. It will work correctly, right?
>
>>> NOTE: I am not proposing that the address is made available to the EFI
>>> application - that would always see the sandbox pointer.
>>
>> In that case it's *much* easier to just always store host pointers in the
>> efi memory map. Everything else will be very intrusive.
> Yes there will be map_sysmem() and map_to_sysmem() calls at each
> boundary. That 'intrusion' is what we have everywhere in sandbox and
> it is how things work. But the nice thing is that the tables don't end
> up with 'private' sandbox addresses in them. Also see me comments
> above.
I seem to be missing the point. efi_loader is just a tiny shim layer
whose only purpose it is to interface between the binary efi interface
and U-Boot internal code. So why shouldn't efi_loader treat addresses as
pointers internally?
So how about this: I'll send out a patch set that works the way I think
is the right way forward. With this I can at least run binaries
generated by gnu-efi. Then you can send a patch on top with a proposal
how you think the mapping should happen. My guess is that your patch
will just clutter the code, but I'll be happy to be persuaded otherwise.
Alex
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