Re: grub EFI "too little memory"

[Andrei E. Warkentin]

Exactly on target.  Then we need a more robust and permanent solution I think right?

How about asking with 0 sized buffer first knowing it will fail then asking with a rounded-up buffer the 2nd time.
I can coded it, but I can't check it in of course.

http://www.uefi.org/specs/

You shouldn't assume memory map size (in fact, it can change during the runtime if you use AllocatePool/FreePool/AllocatePages/FreePages), and should be something like...

UINTN currentMemoryMapSize = 0;

UINTN expectedMemoryMapSize = 0;

EFI_MEMORY_DESCRIPTOR *memoryMap = NULL;

UINTN mapKey;

UINTN descriptorSize;

UINT32 descriptorVersion;

EFI_STATUS status = EFI_BUFFER_TOO_SMALL;

while(status == EFI_BUFFER_TOO_SMALL)

{

 status = gBS->GetMemoryMap(&expectedMemoryMapSize, &memoryMap, &mapKey, &descriptorSize, &descriptorVersion);

if(status !=  EFI_BUFFER_TOO_SMALL)

{

break;

}

// May have allocated already...

if(currentMemorySize)

{

status = gBS->FreePool(memoryMap);

if(EFI_ERROR(status))

{

break;

}

}

// As per spec, allocate more than requested to handle growth of memory map due to allocation).

expectedMemorySize = expectedMemorySize * 2;

status = gBS->AllocatePool(EfiLoaderData, expectedMemoryMapSize, (VOID**) &memoryMap);

currentMemoryMapSize = expectedMemoryMapSize;

if(EFI_ERROR(status))

{

break;

}

// Make sure we retry to get the memory map.

status = EFI_BUFFER_TOO_SMALL;

}

if(EFI_ERROR(status) || currentMemoryMapSize == 0)

{

// No memory map, assorted errors....

}

// Loop over the memoryMapSize array using descriptorSize (_NOT_ sizeof(EFI_MEMORY_DESCRIPTOR)), as that could break for future EFI versions where the descriptor size might increase with expansion).

// Free pool. 

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