[PATCH v2 0/5] x86/efi: Re-enable memory attributes table for kexec

Ard Biesheuvel
2026-04-01T12:24:06Z

From: Ard Biesheuvel <ardb@kernel.org>

The EFI memory attributes table augments the EFI memory map, and
provides permission attributes for all runtime code and data regions
that are otherwise mapped read-write-execute in their entirety.

Currently, this table is disregarded when doing kexec boot on x86, for
two reasons:
- the boot services data region that holds the table is not reserved
correctly, and may contain garbage at kexec time
- a misguided sanity check on the size of the table is likely to trigger
on kexec, as the EFI memory map has been trimmed down by that time.

Fix both issues, so that the EFI memory attributes table can be taken
into account again at kexec time. Note that this requires that the call
to efi_memattr_init() is moved to a later point for x86.

Changes since v1:
- Sanity check the descriptor size and entry count individually: this
prevents integer overflow, and avoid noisy diagnostics when using
kexec_load(), which reconstructs the EFI memory map using a different
descriptor size.
- Apply Gregory's Rb to patch #1 (but not patch #1)

I'd like to take this through the EFI tree as a whole, or take the
first patch now (which is a fix) and leave the rest for -tip during the
next cycle. (Patches #3 and #4 should be queued together in any case)

Cc: Dave Young <dyoung@redhat.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Breno Leitao <leitao@debian.org>

Ard Biesheuvel (5):
efi/memattr: Fix thinko in table size sanity check
x86/efi: Gather initial memory reservation and table handling logic
x86/efi: Defer the call to efi_memattr_init()
efi: Use efi_mem_reserve() to reserve the memory attribute table
x86/efi: Drop kexec quirk for the EFI memory attributes table

arch/x86/include/asm/efi.h | 5 +--
arch/x86/kernel/setup.c | 11 +-----
arch/x86/platform/efi/efi.c | 15 ++++++++
arch/x86/platform/efi/quirks.c | 4 --
drivers/firmware/efi/efi.c | 2 +-
drivers/firmware/efi/memattr.c | 39 +++++++++++++++-----
6 files changed, 49 insertions(+), 27 deletions(-)

base-commit: d0c3bcd5b8976159d835a897254048e078f447e6
--
2.53.0.1118.gaef5881109-goog