Currently, all platforms will set up their heap on initialization of the
platform code. While this works mostly fine, it poses some limitations
on memory management on us. Most notably, allocating big chunks of
memory in the gigabyte range would require us to pre-request this many
bytes from the firmware and add it to the heap from the beginning on
some platforms like EFI. As this isn't needed for most configurations,
it is inefficient and may even negatively impact some usecases when,
e.g., chainloading. Nonetheless, allocating big chunks of memory is
required sometimes, where one example is the upcoming support for the
Argon2 key derival function in LUKS2.
In order to avoid pre-allocating big chunks of memory, this commit
implements a runtime mechanism to add more pages to the system. When
a given allocation cannot be currently satisfied, we'll call a given
callback set up by the platform's own memory management subsystem,
asking it to add a memory area with at least "n" bytes. If this
succeeds, we retry searching for a valid memory region, which should
now succeed.
If this fails, we try asking for "n" bytes, possibly spread across
multiple regions, in hopes that region merging means that we end up
with enough memory for things to work out.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Daniel Axtens <dja@axtens.net>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Patrick Steinhardt <ps@pks.im>
In grub_memalign(), there's a commented section which would allow for
unloading of unneeded modules in case where there is not enough free
memory available to satisfy a request. Given that this code is never
compiled in, let's remove it together with grub_dl_unload_unneeded().
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Patrick Steinhardt <ps@pks.im>
This is handy for debugging. Enable with "set debug=regions".
Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Patrick Steinhardt <ps@pks.im>
On x86_64-efi (at least) regions seem to be added from top down. The mm
code will merge a new region with an existing region that comes
immediately before the new region. This allows larger allocations to be
satisfied that would otherwise be the case.
On powerpc-ieee1275, however, regions are added from bottom up. So if
we add 3x 32MB regions, we can still only satisfy a 32MB allocation,
rather than the 96MB allocation we might otherwise be able to satisfy.
* Define 'post_size' as being bytes lost to the end of an allocation
due to being given weird sizes from firmware that are not multiples
of GRUB_MM_ALIGN.
* Allow merging of regions immediately _after_ existing regions, not
just before. As with the other approach, we create an allocated
block to represent the new space and the pass it to grub_free() to
get the metadata right.
Signed-off-by: Daniel Axtens <dja@axtens.net>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Patrick Steinhardt <ps@pks.im>
The grub_mm_init_region() does some things that seem magical, especially
around region merging. Make it a bit clearer.
Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
The grub_free() possesses a surprising number of quirks, and also
uses single-letter variable names confusingly to iterate through
the free list.
Document what's going on.
Use prev and cur to iterate over the free list.
Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Small allocations move the region's *first pointer. The comment
says that this happens for allocations under 64K. The code says
it's for allocations under 32K. Commit 45bf8b3a75 changed the
code intentionally: make the comment match.
Fixes: 45bf8b3a75 (* grub-core/kern/mm.c (grub_real_malloc): Decrease cut-off of moving the)
Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
When iterating through the singly linked list of free blocks,
grub_real_malloc() uses p and q for the current and previous blocks
respectively. This isn't super clear, so swap to using prev and cur.
This makes another quirk more obvious. The comment at the top of
grub_real_malloc() might lead you to believe that the function will
allocate from *first if there is space in that block.
It actually doesn't do that, and it can't do that with the current
data structures. If we used up all of *first, we would need to change
the ->next of the previous block to point to *first->next, but we
can't do that because it's a singly linked list and we don't have
access to *first's previous block.
What grub_real_malloc() actually does is set *first to the initial
previous block, and *first->next is the block we try to allocate
from. That allows us to keep all the data structures consistent.
Document that.
Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Fix compilation error due to missing parameter to
grub_printf() when MM_DEBUG is defined.
Fixes: 64e26162e (calloc: Make sure we always have an overflow-checking calloc() available)
Signed-off-by: Marco A Benatto <mbenatto@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This tries to make sure that everywhere in this source tree, we always have
an appropriate version of calloc() (i.e. grub_calloc(), xcalloc(), etc.)
available, and that they all safely check for overflow and return NULL when
it would occur.
Signed-off-by: Peter Jones <pjones@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
pointer to 32K. This is the size of cache element which is the most
common allocation >1K. This way the pointer is always around blocks
of 32K and so we keep performance while decreasing fragmentation.
