Re: [edk2-devel] [PATCH 1/1] StandaloneMmPkg/Core: Remove optimization for depex evaluation

["levi.yun" <yeoreum.yun@arm.com>]

Except, 8bit transfer encoding.

Tested-by: levi.yun <yeoreum.yun@arm.com>
Reviewed-by: levi.yun <yeoreum.yun@arm.com>

On 19/01/2024 10:39, Ard Biesheuvel via groups.io wrote:
> On Fri, 19 Jan 2024 at 05:58, Nhi Pham via groups.io
> <nhi=os.amperecomputing.com@groups.io> wrote:
>> From: Laszlo Ersek <lersek@redhat.com>
>>
>> The current dependency evaluator violates the memory access permission
>> when patching depex grammar directly in the read-only depex memory area.
>>
>> Laszlo pointed out the optimization issue in the thread (1) "Memory
>> Attribute for depex section" and provided suggested patch to remove the
>> perf optimization.
>>
>> In my testing, removing the optimization does not make significant perf
>> reduction. That makes sense that StandaloneMM dispatcher only searches
>> in MM protocol database and does not depend on UEFI/DXE protocol
>> database. Also, we don't have many protocols in StandaloneMM like
>> UEFI/DXE.
>>
>>  From Laszlo,
>>
>> "The patch removes the EFI_DEP_REPLACE_TRUE handling altogether, plus it
>> CONST-ifies the Iterator pointer (which points into the DEPEX section),
>> so that the compiler catch any possible accesses at *build time* that
>> would write to the write-protected DEPEX memory area."
>>
>> (1) https://edk2.groups.io/g/devel/message/113531
>>
>> Signed-off-by: Nhi Pham <nhi@os.amperecomputing.com>
> Thanks for the patch. This looks good to me in principle, only the
> patch got mangled by your MTA
>
> Please resend using 8bit transfer encoding. (You can use
> BaseTools/Scripts/SetupGit.py to configure Git for you)
>
>
>> ---
>>   StandaloneMmPkg/Core/Dependency.c | 37 ++++----------------
>>   1 file changed, 7 insertions(+), 30 deletions(-)
>>
>> diff --git a/StandaloneMmPkg/Core/Dependency.c b/StandaloneMmPkg/Core/Dependency.c
>> index 440fe3e45238..2bcb07d34666 100644
>> --- a/StandaloneMmPkg/Core/Dependency.c
>> +++ b/StandaloneMmPkg/Core/Dependency.c
>> @@ -13,16 +13,6 @@
>>
>>
>>   #include "StandaloneMmCore.h"
>>
>>
>>
>> -///
>>
>> -/// EFI_DEP_REPLACE_TRUE - Used to dynamically patch the dependency expression
>>
>> -///                        to save time.  A EFI_DEP_PUSH is evaluated one an
>>
>> -///                        replaced with EFI_DEP_REPLACE_TRUE. If PI spec's Vol 2
>>
>> -///                        Driver Execution Environment Core Interface use 0xff
>>
>> -///                        as new DEPEX opcode. EFI_DEP_REPLACE_TRUE should be
>>
>> -///                        defined to a new value that is not conflicting with PI spec.
>>
>> -///
>>
>> -#define EFI_DEP_REPLACE_TRUE  0xff
>>
>> -
>>
>>   ///
>>
>>   /// Define the initial size of the dependency expression evaluation stack
>>
>>   ///
>>
>> @@ -170,12 +160,12 @@ MmIsSchedulable (
>>     IN  EFI_MM_DRIVER_ENTRY  *DriverEntry
>>
>>     )
>>
>>   {
>>
>> -  EFI_STATUS  Status;
>>
>> -  UINT8       *Iterator;
>>
>> -  BOOLEAN     Operator;
>>
>> -  BOOLEAN     Operator2;
>>
>> -  EFI_GUID    DriverGuid;
>>
>> -  VOID        *Interface;
>>
>> +  EFI_STATUS   Status;
>>
>> +  CONST UINT8  *Iterator;
>>
>> +  BOOLEAN      Operator;
>>
>> +  BOOLEAN      Operator2;
>>
>> +  EFI_GUID     DriverGuid;
>>
>> +  VOID         *Interface;
>>
>>
>>
>>     Operator  = FALSE;
>>
>>     Operator2 = FALSE;
>>
>> @@ -253,8 +243,7 @@ MmIsSchedulable (
>>             Status = PushBool (FALSE);
>>
>>           } else {
>>
>>             DEBUG ((DEBUG_DISPATCH, "  PUSH GUID(%g) = TRUE\n", &DriverGuid));
>>
>> -          *Iterator = EFI_DEP_REPLACE_TRUE;
>>
>> -          Status    = PushBool (TRUE);
>>
>> +          Status = PushBool (TRUE);
>>
>>           }
>>
>>
>>
>>           if (EFI_ERROR (Status)) {
>>
>> @@ -356,18 +345,6 @@ MmIsSchedulable (
>>           DEBUG ((DEBUG_DISPATCH, "  RESULT = %a\n", Operator ? "TRUE" : "FALSE"));
>>
>>           return Operator;
>>
>>
>>
>> -      case EFI_DEP_REPLACE_TRUE:
>>
>> -        CopyMem (&DriverGuid, Iterator + 1, sizeof (EFI_GUID));
>>
>> -        DEBUG ((DEBUG_DISPATCH, "  PUSH GUID(%g) = TRUE\n", &DriverGuid));
>>
>> -        Status = PushBool (TRUE);
>>
>> -        if (EFI_ERROR (Status)) {
>>
>> -          DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unexpected error)\n"));
>>
>> -          return FALSE;
>>
>> -        }
>>
>> -
>>
>> -        Iterator += sizeof (EFI_GUID);
>>
>> -        break;
>>
>> -
>>
>>         default:
>>
>>           DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Unknown opcode)\n"));
>>
>>           goto Done;
>>
>> --
>> 2.25.1
>>
>>
>>
>>
>>
>>
>
> 
>
>

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