Message-ID: <67bff00d-eca7-41bd-ad9c-7ee6d5dac040@linux.ibm.com>
Date: Tue, 18 Mar 2025 11:08:45 +0530
From: Madhavan Srinivasan <maddy@...ux.ibm.com>
To: Andrew Donnellan <ajd@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org
Cc: x86@...nel.org, linux-mm@...ck.org, linux-riscv@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        pasha.tatashin@...een.com, sweettea-kernel@...miny.me
Subject: Re: [PATCH v13 00/11] Support page table check on PowerPC



On 2/11/25 9:43 PM, Andrew Donnellan wrote:
> Support page table check on all PowerPC platforms. This works by
> serialising assignments, reassignments and clears of page table
> entries at each level in order to ensure that anonymous mappings
> have at most one writable consumer, and likewise that file-backed
> mappings are not simultaneously also anonymous mappings.
> 
> In order to support this infrastructure, a number of stubs must be
> defined for all powerpc platforms. Additionally, seperate set_pte_at()
> and set_pte_at_unchecked(), to allow for internal, uninstrumented mappings.
> 
> (This series was written by Rohan McLure, who has left IBM and is no longer
> working on powerpc - I've taken far too long to pick this up and finally
> send it.)
> 

For powerpc changes
Acked-by: Madhavan Srinivasan <maddy@...ux.ibm.com>

> v13:
>  * Rebase on mainline
>  * Don't use set_pte_at_unchecked() for early boot purposes (Pasha)
> 
> v12:
>  * Rename commits that revert changes to instead reflect that we are
>    reinstating old behaviour due to it providing more flexibility
>  * Add return line to pud_pfn() stub
>  * Instrument ptep_get_and_clear() for nohash
> Link: https://lore.kernel.org/linuxppc-dev/20240402051154.476244-1-rmclure@linux.ibm.com/
> 
> v11:
>  * The pud_pfn() stub, which previously had no legitimate users on any
>    powerpc platform, now has users in Book3s64 with transparent pages.
>    Include a stub of the same name for each platform that does not
>    define their own.
>  * Drop patch that standardised use of p*d_leaf(), as already included
>    upstream in v6.9.
>  * Provide fallback definitions of p{m,u}d_user_accessible_page() that
>    do not reference p*d_leaf(), p*d_pte(), as they are defined after
>    powerpc/mm headers by linux/mm headers.
>  * Ensure that set_pte_at_unchecked() has the same checks as
>    set_pte_at().
> Link: https://lore.kernel.org/linuxppc-dev/20240328045535.194800-14-rmclure@linux.ibm.com/ 
> 
> v10:
>  * Revert patches that removed address and mm parameters from page table
>    check routines, including consuming code from arm64, x86_64 and
>    riscv.
>  * Implement *_user_accessible_page() routines in terms of pte_user()
>    where available (64-bit, book3s) but otherwise by checking the
>    address (on platforms where the pte does not imply whether the
>    mapping is for user or kernel)
>  * Internal set_pte_at() calls replaced with set_pte_at_unchecked(), which
>    is identical, but prevents double instrumentation.
> Link: https://lore.kernel.org/linuxppc-dev/20240313042118.230397-9-rmclure@linux.ibm.com/T/
> 
> v9:
>  * Adapt to using the set_ptes() API, using __set_pte_at() where we need
>    must avoid instrumentation.
>  * Use the logic of *_access_permitted() for implementing
>    *_user_accessible_page(), which are required routines for page table
>    check.
>  * Even though we no longer need p{m,u,4}d_leaf(), still default
>    implement these to assist in refactoring out extant
>    p{m,u,4}_is_leaf().
>  * Add p{m,u}_pte() stubs where asm-generic does not provide them, as
>    page table check wants all *user_accessible_page() variants, and we
>    would like to default implement the variants in terms of
>    pte_user_accessible_page().
>  * Avoid the ugly pmdp_collapse_flush() macro nonsense! Just instrument
>    its constituent calls instead for radix and hash.
> Link: https://lore.kernel.org/linuxppc-dev/20231130025404.37179-2-rmclure@linux.ibm.com/
> 
> v8:
>  * Fix linux/page_table_check.h include in asm/pgtable.h breaking
>    32-bit.
> Link: https://lore.kernel.org/linuxppc-dev/20230215231153.2147454-1-rmclure@linux.ibm.com/
> 
> v7:
>  * Remove use of extern in set_pte prototypes
>  * Clean up pmdp_collapse_flush macro
>  * Replace set_pte_at with static inline function
>  * Fix commit message for patch 7
> Link: https://lore.kernel.org/linuxppc-dev/20230215020155.1969194-1-rmclure@linux.ibm.com/
> 
> v6:
>  * Support huge pages and p{m,u}d accounting.
>  * Remove instrumentation from set_pte from kernel internal pages.
>  * 64s: Implement pmdp_collapse_flush in terms of __pmdp_collapse_flush
>    as access to the mm_struct * is required.
> Link: https://lore.kernel.org/linuxppc-dev/20230214015939.1853438-1-rmclure@linux.ibm.com/
> 
> v5:
> Link: https://lore.kernel.org/linuxppc-dev/20221118002146.25979-1-rmclure@linux.ibm.com/
> 
> Rohan McLure (11):
>   mm/page_table_check: Reinstate address parameter in
>     [__]page_table_check_pud_set()
>   mm/page_table_check: Reinstate address parameter in
>     [__]page_table_check_pmd_set()
>   mm/page_table_check: Provide addr parameter to
>     page_table_check_pte_set()
>   mm/page_table_check: Reinstate address parameter in
>     [__]page_table_check_pud_clear()
>   mm/page_table_check: Reinstate address parameter in
>     [__]page_table_check_pmd_clear()
>   mm/page_table_check: Reinstate address parameter in
>     [__]page_table_check_pte_clear()
>   mm: Provide address parameter to p{te,md,ud}_user_accessible_page()
>   powerpc: mm: Add pud_pfn() stub
>   powerpc: mm: Implement *_user_accessible_page() for ptes
>   powerpc: mm: Use set_pte_at_unchecked() for internal usages
>   powerpc: mm: Support page table check
> 
>  arch/arm64/include/asm/pgtable.h             | 18 +++---
>  arch/powerpc/Kconfig                         |  1 +
>  arch/powerpc/include/asm/book3s/32/pgtable.h | 12 +++-
>  arch/powerpc/include/asm/book3s/64/pgtable.h | 62 +++++++++++++++---
>  arch/powerpc/include/asm/nohash/pgtable.h    | 13 +++-
>  arch/powerpc/include/asm/pgtable.h           | 19 ++++++
>  arch/powerpc/mm/book3s64/hash_pgtable.c      |  4 ++
>  arch/powerpc/mm/book3s64/pgtable.c           | 17 +++--
>  arch/powerpc/mm/book3s64/radix_pgtable.c     |  9 ++-
>  arch/powerpc/mm/pgtable.c                    | 12 ++++
>  arch/riscv/include/asm/pgtable.h             | 18 +++---
>  arch/x86/include/asm/pgtable.h               | 20 +++---
>  include/linux/page_table_check.h             | 67 ++++++++++++--------
>  include/linux/pgtable.h                      | 10 +--
>  mm/page_table_check.c                        | 39 +++++++-----
>  15 files changed, 225 insertions(+), 96 deletions(-)
> 

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