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

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Message-ID: <913fdbe4-d77a-4083-8378-4c8a602366a8@lucifer.local>
Date: Wed, 29 Jan 2025 17:28:44 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Mike Rapoport <rppt@...nel.org>
Cc: x86@...nel.org, Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Borislav Petkov <bp@...en8.de>,
        Brendan Higgins <brendan.higgins@...ux.dev>,
        Daniel Gomez <da.gomez@...sung.com>,
        Daniel Thompson <danielt@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Gow <davidgow@...gle.com>,
        Douglas Anderson <dianders@...omium.org>,
        Ingo Molnar <mingo@...hat.com>,
        Jason Wessel <jason.wessel@...driver.com>,
        Jiri Kosina <jikos@...nel.org>, Joe Lawrence <joe.lawrence@...hat.com>,
        Johannes Berg <johannes@...solutions.net>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>, "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>, Petr Mladek <pmladek@...e.com>,
        Petr Pavlu <petr.pavlu@...e.com>, Rae Moar <rmoar@...gle.com>,
        Richard Weinberger <richard@....at>,
        Sami Tolvanen <samitolvanen@...gle.com>, Shuah Khan <shuah@...nel.org>,
        Song Liu <song@...nel.org>, Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        kgdb-bugreport@...ts.sourceforge.net, kunit-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-mm@...ck.org, linux-modules@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, linux-um@...ts.infradead.org,
        live-patching@...r.kernel.org
Subject: Re: [PATCH v3 0/9] x86/module: rework ROX cache to avoid writable
 copy

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@...cle.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@...nel.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
>