[GIT PULL v2 0/5] EFI page table isolation

From: Matt Fleming
Date: Sat Nov 14 2015 - 17:01:43 EST


This patch series is a response to the report that the EFI region
mappings trigger warnings when booting with CONFIG_DEBUG_WX enabled.
They allocate a new page table structure and ensure that all the
mappings we require during EFI runtime calls are only setup there.

It turns out that it still makes sense to share some page table
entries with 'swapper_pg_dir', just not the entries where we need to
allow security lax permissions. Sharing entries is useful for memory
hotplug, for example.

When writing this series I discovered a number of bugs in the existing
code that only became apparent when we stopped using 'trampoline_pgd'
which already mapped a bunch of things for us. I've put those bug
fixes at the start of the series.

Further testing would be very much appreciated as this is a
notoriously funky area of the EFI code.

Changes in v2:

- Folded PATCH 1 and 2 together because they both fall under the
umbrella of "making sure cpa->pfn is really a page frame number".

- Fixed some checkpatch warnings about mixing spaces and tabs and
made some stylistic changes per Borislav's comments.

- Moved efi_alloc_page_tables() earlier in __efi_enter_virtual_mode()
so that we fail early if we can't allocate memory for the page

The following changes since commit 2c66e24d75d424919c42288b418d2e593fa818b1:

x86/efi: Fix kernel panic when CONFIG_DEBUG_VIRTUAL is enabled (2015-10-25 10:22:25 +0000)

are available in the git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/mfleming/efi.git tags/efi-next

for you to fetch changes up to 78b112115dd6e01ebeaedde4fb4602d718bfba4b:

Documentation/x86: Update EFI memory region description (2015-11-14 21:40:02 +0000)

* Use completely separate page tables for EFI runtime service calls
so that the security-lax mapping permissions (RWX) do not leak into
the standard kernel page tables and trigger warnings when
CONFIG_DEBUG_WX is enabled.

Matt Fleming (5):
x86/mm/pageattr: Ensure cpa->pfn only contains page frame numbers
x86/efi: Map RAM into the identity page table for mixed mode
x86/efi: Hoist page table switching code into efi_call_virt()
x86/efi: Build our own page table structures
Documentation/x86: Update EFI memory region description

Documentation/x86/x86_64/mm.txt | 12 +--
arch/x86/include/asm/efi.h | 26 ++++++
arch/x86/mm/pageattr.c | 17 ++--
arch/x86/platform/efi/efi.c | 39 +++-----
arch/x86/platform/efi/efi_32.c | 5 ++
arch/x86/platform/efi/efi_64.c | 174 ++++++++++++++++++++++++++++--------
arch/x86/platform/efi/efi_stub_64.S | 43 ---------
7 files changed, 192 insertions(+), 124 deletions(-)
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