Re: [PATCH] ArmPlatformPkg/PrePeiCore: seed temporary stack before entering PEI core

[Laszlo Ersek <lersek@redhat.com>]

On 10/20/17 18:10, Ard Biesheuvel wrote:
> On 20 October 2017 at 16:43, Laszlo Ersek <lersek@redhat.com> wrote:
>> On 10/20/17 15:00, Leif Lindholm wrote:
>>> On Fri, Oct 20, 2017 at 12:23:25PM +0100, Ard Biesheuvel wrote:
>>>> DEBUG builds of PEI code will print a diagnostic message regarding
>>>> the utilization of temporary RAM before switching to permanent RAM.
>>>> For example,
>>>>
>>>>   Total temporary memory:    16352 bytes.
>>>>     temporary memory stack ever used:       4820 bytes.
>>>>     temporary memory heap used for HobList: 4720 bytes.
>>>>
>>>> Tracking stack utilization like this requires the stack to be seeded
>>>> with a known magic value, and this needs to occur before entering C
>>>> code, given that it uses the stack. Currently, only Nt32Pkg appears
>>>> to implement this feature, but it is useful nonetheless, so let's
>>>> wire it up for PrePeiCore.
>>>>
>>>> Contributed-under: TianoCore Contribution Agreement 1.1
>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>>> ---
>>>>  ArmPlatformPkg/PrePeiCore/AArch64/PrePeiCoreEntryPoint.S |  7 +++++++
>>>>  ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.S     | 10 ++++++++++
>>>>  ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.asm   | 10 ++++++++++
>>>>  3 files changed, 27 insertions(+)
>>>>
>>>> diff --git a/ArmPlatformPkg/PrePeiCore/AArch64/PrePeiCoreEntryPoint.S b/ArmPlatformPkg/PrePeiCore/AArch64/PrePeiCoreEntryPoint.S
>>>> index aab5edab0c42..7a33e2754869 100644
>>>> --- a/ArmPlatformPkg/PrePeiCore/AArch64/PrePeiCoreEntryPoint.S
>>>> +++ b/ArmPlatformPkg/PrePeiCore/AArch64/PrePeiCoreEntryPoint.S
>>>> @@ -13,6 +13,8 @@
>>>>
>>>>  #include <AsmMacroIoLibV8.h>
>>>>
>>>> +#define INIT_CAR_VALUE      0x5AA55AA55AA55AA5
>>>> +
>>>>  ASM_FUNC(_ModuleEntryPoint)
>>>>    // Do early platform specific actions
>>>>    bl    ASM_PFX(ArmPlatformPeiBootAction)
>>>> @@ -84,4 +86,9 @@ _PrepareArguments:
>>>>
>>>>  _SetupPrimaryCoreStack:
>>>>    mov   sp, x1
>>>> +  MOV64 (x8, FixedPcdGet64(PcdCPUCoresStackBase))
>>>> +  MOV64 (x9, INIT_CAR_VALUE)
>>>> +0:stp   x9, x9, [x8], #16
>>>> +  cmp   x8, x1
>>>> +  b.lt  0b
>>>>    b     _PrepareArguments
>>>> diff --git a/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.S b/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.S
>>>> index 14344425ad4c..7342e49bea59 100644
>>>> --- a/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.S
>>>> +++ b/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.S
>>>> @@ -13,6 +13,8 @@
>>>>
>>>>  #include <AsmMacroIoLib.h>
>>>>
>>>> +#define INIT_CAR_VALUE      0x5AA55AA5
>>>> +
>>>
>>> Worth moving to a common header somewhere?
>>>
>>> Also defined/used in MdeModulePkg/Core/Pei/Dispatcher/Dispatcher.c.
>>
>> Furthermore, open-coded in:
>>
>> EmulatorPkg/Unix/Host/Host.c:    *StackPointer = 0x5AA55AA5;
>> Nt32Pkg/Sec/SecMain.c:    *StackPointer = 0x5AA55AA5;
>>
>> Honestly I think it should be a Fixed-At-Build PCD, in MdeModulePkg.dec,
>> similarly to
>>
>>   gEfiMdePkgTokenSpaceGuid.PcdDebugClearMemoryValue
>>
>> in MdePkg.dec.
>>
> 
> Yes. And you both know how the MdeModulePkg maintainers are going to
> respond if I propose adding another PCD.

Yes, I can certainly see myself on the "wrong end" of that patch. :(

Acked-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo

> 
>> I'm unhappy that we have to annoy Ard with a request to "upstream" this
>> constant to MdeModulePkg in some form, but we'll need it yet again in
>> OVMF...
>>
> 
> 
>>>
>>> That file has an explicit comment saying "temporary memory is filled
>>> with this initial value during SEC phase". Should this end have a
>>> corresponding comment saying "checked for during PEI phase"?
>>
>> Thanks
>> Laszlo
>>
>>>
>>> /
>>>     Leif
>>>
>>>>  ASM_FUNC(_ModuleEntryPoint)
>>>>    // Do early platform specific actions
>>>>    bl    ASM_PFX(ArmPlatformPeiBootAction)
>>>> @@ -65,6 +67,14 @@ _PrepareArguments:
>>>>
>>>>  _SetupPrimaryCoreStack:
>>>>    mov   sp, r1
>>>> +  MOV32 (r8, FixedPcdGet64(PcdCPUCoresStackBase))
>>>> +  MOV32 (r9, INIT_CAR_VALUE)
>>>> +  mov   r10, r9
>>>> +  mov   r11, r9
>>>> +  mov   r12, r9
>>>> +0:stm   r8!, {r9-r12}
>>>> +  cmp   r8, r1
>>>> +  blt   0b
>>>>    b     _PrepareArguments
>>>>
>>>>  _NeverReturn:
>>>> diff --git a/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.asm b/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.asm
>>>> index abea675828df..7455de8aa66e 100644
>>>> --- a/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.asm
>>>> +++ b/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.asm
>>>> @@ -13,6 +13,8 @@
>>>>
>>>>  #include <AutoGen.h>
>>>>
>>>> +#define INIT_CAR_VALUE      0x5AA55AA5
>>>> +
>>>>    INCLUDE AsmMacroIoLib.inc
>>>>
>>>>    IMPORT  CEntryPoint
>>>> @@ -79,6 +81,14 @@ _PrepareArguments
>>>>
>>>>  _SetupPrimaryCoreStack
>>>>    mov   sp, r1
>>>> +  mov32 r8, FixedPcdGet64(PcdCPUCoresStackBase)
>>>> +  mov32 r9, INIT_CAR_VALUE
>>>> +  mov   r10, r9
>>>> +  mov   r11, r9
>>>> +  mov   r12, r9
>>>> +0:stm   r8!, {r9-r12}
>>>> +  cmp   r8, r1
>>>> +  blt   0b
>>>>    b     _PrepareArguments
>>>>
>>>>  _NeverReturn
>>>> --
>>>> 2.11.0
>>>>
>>