Re: [edk2-devel] Peims are not gettting Dispatched in EagleStream Platform

["Laszlo Ersek" <lersek@redhat.com>]

On 2/21/24 07:59, memristor2 via groups.io wrote:
> Hi,
> I am trying to build edk2-platforms for EagleStream Platform. The
> problem I am facing now is that the Peims are not getting dispatched
> when The PeiMain routine calls PeiDispatcher().
> After digging deeper into it it seems that the DepexSatisfied() routine
> is always returning false. So I also checked this and realized that the
> place that is returning false is inside the PeimDispatchReadiness
> function:
> ||​```
> case (EFI_DEP_END):        DEBUG ((DEBUG_DISPATCH, "  END\n"));
>         StackPtr--;
>         //
>         // Check to make sure EvalStack is balanced.  If not, then there is
>         // an error in the dependency grammar, so return
> EFI_INVALID_PARAMETER.
>         //
>         if (StackPtr != &EvalStack[0]) {
>  
>           DEBUG ((DEBUG_DISPATCH, "  RESULT = FALSE (Underflow Error)\n"));
>           return FALSE;
>         }
> 
>         DEBUG ((DEBUG_DISPATCH, "  RESULT = %a\n",
> IsPpiInstalled (PeiServices, StackPtr) ? "TRUE" : "FALSE"));
> 
>         return IsPpiInstalled (PeiServices, StackPtr);
> ```
> It seems that when entering IsPpiInstalled StackPtr in always NULL.
> Any thoughts on this?

StackPtr being NULL seems extremely unlikely; it is supposed to point to
elements of the EvalStack local array (or I guess one past the last
element).

Now, I can see two potential problems here:

- your depex is malformed (for whatever reason), and the eval stack is
not torn down entirely before reachig EFI_DEP_END. The code seems to
handle that correctly, by returning FALSE.

- your depex is malformed such that it immediately starts with an
EFI_DEP_END. The code is actually buggy for that case, because it
decrements StackPtr *first*, before comparing it against &EvalStack[0].
That decrement invokes undefined behavior. However, I assume in practice
the behavior will be the same as in the previous paragraph.

A NULL StackPtr value I cannot explain at all.

Laszlo



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