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

Lorenzo Stoakes
2025-01-29T17:30:08Z

Hi Mike,

I bisected issues with the kernel booting correctly to an earlier revision
of this series [2]. I have now tested this series in the same environment
and found that it functions correctly with no issues, so feel free to add:

Tested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

Cheers, Lorenzo

[2]:https://lore.kernel.org/linux-mm/86eba318-464b-4b9b-a79e-64039b17be34@lucifer.local/

On Sun, Jan 26, 2025 at 09:47:24AM +0200, Mike Rapoport wrote:
> 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
>