Re: EmulatorPkg Unix Host Segmentation fault.

["Ni, Ray" <ray.ni@Intel.com>]

On 2/16/2019 3:43 PM, Ni, Ray wrote:
> (Sent third times to make sure Andrew and Laszlo are in the TO list.)
> 
> I also met this issue.
> I found three solutions:
> 1. Forcing PeiMain CC flag to "-O0" works.
> 2. Changing EmulatorPkg/Sec to not produce TemporaryRamSupportPpi also 
> works.
> 3. Implement the temporary migration routine as below in EmulatorPkg/Sec 
> module.
> 
> EFI_STATUS
> EFIAPI
> SecTemporaryRamSupport (
>    IN CONST EFI_PEI_SERVICES   **PeiServices,
>    IN EFI_PHYSICAL_ADDRESS     TemporaryMemoryBase,
>    IN EFI_PHYSICAL_ADDRESS     PermanentMemoryBase,
>    IN UINTN                    CopySize
>    )
> {
>    VOID                             *OldHeap;
>    VOID                             *NewHeap;
>    VOID                             *OldStack;
>    VOID                             *NewStack;
>    UINTN                            StackMigrateOffset;
>    BASE_LIBRARY_JUMP_BUFFER         JumpBuffer;
> 
>    DEBUG ((EFI_D_INFO,
>      "TemporaryRamMigration(0x%Lx, 0x%Lx, 0x%Lx)\n",
>      TemporaryMemoryBase,
>      PermanentMemoryBase,
>      (UINT64)CopySize
>      ));
> 
>    //
>    // Assume Host prepare the stack and heap in the temprary ram that stack
>    // is below heap (stack is in smaller address).
>    // Stack/heap migration depends on the stack/heap location information
>    // in the temporary ram.
>    //
>    OldStack = (VOID*)(UINTN)TemporaryMemoryBase;
>    NewStack = (VOID*)((UINTN)PermanentMemoryBase);
> 
>    OldHeap = (VOID*)((UINTN)TemporaryMemoryBase + (CopySize >> 1));
>    NewHeap = (VOID*)((UINTN)PermanentMemoryBase + (CopySize >> 1));
> 
>    StackMigrateOffset = (UINTN)NewStack - (UINTN)OldStack;
> 
>    //
>    // Migrate Heap and Stack
>    //
>    CopyMem (NewHeap, OldHeap, CopySize >> 1);
>    CopyMem (NewStack, OldStack, CopySize >> 1);
> 
>    //
>    // Use SetJump()/LongJump() to switch to a new stack.
>    //
>    if (SetJump (&JumpBuffer) == 0) {
> #if defined (MDE_CPU_IA32)
>      JumpBuffer.Esp = JumpBuffer.Esp + StackMigrateOffset;
>      JumpBuffer.Ebp = JumpBuffer.Ebp + StackMigrateOffset;
> #endif
> #if defined (MDE_CPU_X64)
>      JumpBuffer.Rsp = JumpBuffer.Rsp + StackMigrateOffset;
>      JumpBuffer.Rbp = JumpBuffer.Rbp + StackMigrateOffset;
> #endif
>      LongJump (&JumpBuffer, (UINTN)-1);
>    }
> 
>    ZeroMem ((VOID *)(UINTN) TemporaryMemoryBase, CopySize);
> 
>    return EFI_SUCCESS;
> }
> 
> 
> Andrew,
> I'd like to know why you chose to produce the migration PPI from
> EmulatorPkg/Sec module.
> Based on PI spec and current PeiCore implementation, PeiCore can do the 
> migration when PPI is absent.
> 
> 
> 
Study the PeiCore migration logic a bit more, I found since PeiCore 
knows the exact size of new stack in permanent memory, it migrates the 
old stack to the top of new stack.
But the migration logic in above C code (since it doesn't know the size 
of new stack, CopySize is the size of temporary memory) may copy the old 
stack to the middle in new stack.

-- 
Thanks,
Ray