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Re: [PATCH v3 2/2] efi: Free malloc regions on exit

From: Alexander Graf
Subject: Re: [PATCH v3 2/2] efi: Free malloc regions on exit
Date: Tue, 29 Aug 2017 20:45:32 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.6.0

On 08/29/2017 08:25 PM, Leif Lindholm wrote:
On Tue, Aug 29, 2017 at 06:00:35PM +0200, Alexander Graf wrote:
When we exit grub, we don't free all the memory that we allocated earlier
for our heap region. This can cause problems with setups where you try
to descend the boot order using "exit" entries, such as PXE -> HD boot

Signed-off-by: Alexander Graf <address@hidden>
Really happy to see this, but repeating a comment here from irc:
This deals with the biggest problem with returning to UEFI - GRUB
allocates 25% of available RAM, which before this patch we don't
release. However, various operations may allocate EFI memory directly,
and those allocations are not currently being tracked.

If further allocations could be tracked from
grub_efi_allocate_pages_real, these could be unwound in
_memory_fini(). Those can safely be allocated from the heap.

I'm using pool allocations now which *usually* go into a malloc like pool on the UEFI side anyway, hence I don't think we should complicate the logic even more and differentiate between heap and non-heap allocations. I'll just add all allocations from efi_allocate_pages_real() to the list and free them on exit - that should be safest.


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