Re: [PATCH] ArmVirtPkg/ArmVirtQemuKernel: increase slack space for DTB

[Michael Zimmermann <sigmaepsilon92@gmail.com>]

"contains some scratch memory at the start of the image to use as a
stack very early on"
When does this happen? I didn't see any edk2-code which sets SP to the
slack space.

Thanks
Michael

On Tue, Apr 4, 2017 at 5:02 PM, Ard Biesheuvel
<ard.biesheuvel@linaro.org> wrote:
> On 4 April 2017 at 15:59, Laszlo Ersek <lersek@redhat.com> wrote:
>> On 04/04/17 16:45, Ard Biesheuvel wrote:
>>> The relocatable build of ArmVirtQemuKernel is designed to be executed
>>> from RAM, and contains some scratch memory at the start of the image
>>> to use as a stack very early on, and to preserve the DTB image received
>>> from QEMU while it discovers and initializes memory.
>>>
>>> It turns out that 8 KB is a bit on the small side here, especially when
>>> executing with secure world emulation enabled, in which case there are
>>> additional nodes present.
>>>
>>> So increase the slack space to 32 KB.
>>>
>>> While at it, remove a stale Xen reference that was copy/pasted when this
>>> file was created.
>>>
>>> Contributed-under: TianoCore Contribution Agreement 1.0
>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>> ---
>>>  ArmVirtPkg/ArmVirtQemuKernel.fdf | 12 ++++++------
>>>  1 file changed, 6 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/ArmVirtPkg/ArmVirtQemuKernel.fdf b/ArmVirtPkg/ArmVirtQemuKernel.fdf
>>> index 7bc62f6b0b48..55541a1075d8 100644
>>> --- a/ArmVirtPkg/ArmVirtQemuKernel.fdf
>>> +++ b/ArmVirtPkg/ArmVirtQemuKernel.fdf
>>> @@ -52,15 +52,15 @@ [FD.QEMU_EFI]
>>>  ################################################################################
>>>
>>>  #
>>> -# Implement the Linux kernel header layout so that the Xen loader will identify
>>> +# Implement the Linux kernel header layout so that the loader will identify
>>>  # it as something bootable, and execute it with a FDT pointer in x0 or r2.
>>> -# This area will be reused to store a copy of the FDT so round it up to 8 KB.
>>> +# This area will be reused to store a copy of the FDT so round it up to 32 KB.
>>>  #
>>> -0x00000000|0x00002000
>>> +0x00000000|0x00008000
>>>  DATA = {
>>>  !if $(ARCH) == AARCH64
>>>    0x01, 0x00, 0x00, 0x10,                         # code0: adr x1, .
>>> -  0xff, 0x07, 0x00, 0x14,                         # code1: b 0x2000
>>> +  0xff, 0x1f, 0x00, 0x14,                         # code1: b 0x8000
>>>    0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, # text_offset: 512 KB
>>>    0x00, 0x00, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, # image_size: 2 MB
>>>    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, # flags
>>> @@ -79,7 +79,7 @@ [FD.QEMU_EFI]
>>>    0x00, 0x00, 0xa0, 0xe1, # nop
>>>    0x00, 0x00, 0xa0, 0xe1, # nop
>>>
>>> -  0xf6, 0x07, 0x00, 0xea, # b 0x2000
>>> +  0xf6, 0x1f, 0x00, 0xea, # b 0x8000
>>>    0x18, 0x28, 0x6f, 0x01, # magic
>>>    0x00, 0x00, 0x00, 0x00, # start
>>>    0x00, 0x00, 0x20, 0x00, # image size: 2 MB
>>> @@ -87,7 +87,7 @@ [FD.QEMU_EFI]
>>>  !endif
>>>  }
>>>
>>> -0x00002000|0x001fe000
>>> +0x00008000|0x001f8000
>>>  gArmTokenSpaceGuid.PcdFvBaseAddress|gArmTokenSpaceGuid.PcdFvSize
>>>  FV = FVMAIN_COMPACT
>>>
>>>
>>
>> Acked-by: Laszlo Ersek <lersek@redhat.com>
>
> Thanks. Pushed as 4d2ea2616e94
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