[PATCH v3 0/9] x86/module: rework ROX cache to avoid writable copy

Mike Rapoport
2025-01-26T07:47:52Z

From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

Hi,

Following Peter's comments [1] these patches rework handling of ROX caches
for module text allocations.

Instead of using a writable copy that really complicates alternatives
patching, temporarily remap parts of a large ROX page as RW for the time of
module formation and then restore it's ROX protections when the module is
ready.

To keep the ROX memory mapped with large pages, make set_memory_rox()
capable of restoring large pages (more details are in patch 3).

Since this is really about x86, I believe this should go in via tip tree.

The patches also available in git
https://git.kernel.org/rppt/h/execmem/x86-rox/v10

v3 changes:
* instead of adding a new module state handle ROX restoration locally in
load_module() as Petr suggested

v2: https://lore.kernel.org/all/20250121095739.986006-1-rppt@kernel.org
* only collapse large mappings in set_memory_rox()
* simplify RW <-> ROX remapping
* don't remove ROX cache pages from the direct map (patch 4)

v1: https://lore.kernel.org/all/20241227072825.1288491-1-rppt@kernel.org

[1] https://lore.kernel.org/all/20241209083818.GK8562@noisy.programming.kicks-ass.net

Kirill A. Shutemov (1):
x86/mm/pat: restore large ROX pages after fragmentation

Mike Rapoport (Microsoft) (8):
x86/mm/pat: cpa-test: fix length for CPA_ARRAY test
x86/mm/pat: drop duplicate variable in cpa_flush()
execmem: don't remove ROX cache from the direct map
execmem: add API for temporal remapping as RW and restoring ROX afterwards
module: switch to execmem API for remapping as RW and restoring ROX
Revert "x86/module: prepare module loading for ROX allocations of text"
module: drop unused module_writable_address()
x86: re-enable EXECMEM_ROX support

arch/um/kernel/um_arch.c | 11 +-
arch/x86/Kconfig | 1 +
arch/x86/entry/vdso/vma.c | 3 +-
arch/x86/include/asm/alternative.h | 14 +-
arch/x86/include/asm/pgtable_types.h | 2 +
arch/x86/kernel/alternative.c | 181 +++++++++-------------
arch/x86/kernel/ftrace.c | 30 ++--
arch/x86/kernel/module.c | 45 ++----
arch/x86/mm/pat/cpa-test.c | 2 +-
arch/x86/mm/pat/set_memory.c | 220 ++++++++++++++++++++++++++-
include/linux/execmem.h | 31 ++++
include/linux/module.h | 16 --
include/linux/moduleloader.h | 4 -
include/linux/vm_event_item.h | 2 +
kernel/module/main.c | 78 +++-------
kernel/module/strict_rwx.c | 9 +-
mm/execmem.c | 39 +++--
mm/vmstat.c | 2 +
18 files changed, 422 insertions(+), 268 deletions(-)

base-commit: ffd294d346d185b70e28b1a28abe367bbfe53c04
--
2.45.2