torvalds/linux
torvalds/linux
2
0
Fork 0
mirror of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-09-04 20:19:47 +08:00
Code
1,382,380 Commits 2 Branches 898 Tags 3.4 GiB
C 97.4%
Assembly 1%
Shell 0.5%
Python 0.4%
Makefile 0.3%
Other 0.2%
f2d2f9598e
Go to file
Harry Yoo f2d2f9598e mm: introduce and use {pgd,p4d}_populate_kernel() 
Introduce and use {pgd,p4d}_populate_kernel() in core MM code when
populating PGD and P4D entries for the kernel address space.  These
helpers ensure proper synchronization of page tables when updating the
kernel portion of top-level page tables.

Until now, the kernel has relied on each architecture to handle
synchronization of top-level page tables in an ad-hoc manner.  For
example, see commit 9b861528a8 ("x86-64, mem: Update all PGDs for direct
mapping and vmemmap mapping changes").

However, this approach has proven fragile for following reasons:

  1) It is easy to forget to perform the necessary page table
     synchronization when introducing new changes.
     For instance, commit 4917f55b4e ("mm/sparse-vmemmap: improve memory
     savings for compound devmaps") overlooked the need to synchronize
     page tables for the vmemmap area.

  2) It is also easy to overlook that the vmemmap and direct mapping areas
     must not be accessed before explicit page table synchronization.
     For example, commit 8d400913c2 ("x86/vmemmap: handle unpopulated
     sub-pmd ranges")) caused crashes by accessing the vmemmap area
     before calling sync_global_pgds().

To address this, as suggested by Dave Hansen, introduce _kernel() variants
of the page table population helpers, which invoke architecture-specific
hooks to properly synchronize page tables.  These are introduced in a new
header file, include/linux/pgalloc.h, so they can be called from common
code.

They reuse existing infrastructure for vmalloc and ioremap. 
Synchronization requirements are determined by ARCH_PAGE_TABLE_SYNC_MASK,
and the actual synchronization is performed by
arch_sync_kernel_mappings().

This change currently targets only x86_64, so only PGD and P4D level
helpers are introduced.  Currently, these helpers are no-ops since no
architecture sets PGTBL_{PGD,P4D}_MODIFIED in ARCH_PAGE_TABLE_SYNC_MASK.

In theory, PUD and PMD level helpers can be added later if needed by other
architectures.  For now, 32-bit architectures (x86-32 and arm) only handle
PGTBL_PMD_MODIFIED, so p*d_populate_kernel() will never affect them unless
we introduce a PMD level helper.

[harry.yoo@oracle.com: fix KASAN build error due to p*d_populate_kernel()]
  Link: https://lkml.kernel.org/r/20250822020727.202749-1-harry.yoo@oracle.com
Link: https://lkml.kernel.org/r/20250818020206.4517-3-harry.yoo@oracle.com
Fixes: 8d400913c2 ("x86/vmemmap: handle unpopulated sub-pmd ranges")
Signed-off-by: Harry Yoo <harry.yoo@oracle.com>
Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Kiryl Shutsemau <kas@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: bibo mao <maobibo@loongson.cn>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Christoph Lameter (Ampere) <cl@gentwo.org>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Huth <thuth@redhat.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-08-27 22:45:44 -07:00
arch - Fix the GDS mitigation detection on some machines after the recent attack 2025-08-24 09:52:28 -04:00
block block: avoid cpu_hotplug_lock depedency on freeze_lock 2025-08-21 07:11:11 -06:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
Documentation Driver core fixes for 6.16-rc3 2025-08-23 09:04:32 -04:00
drivers of_numa: fix uninitialized memory nodes causing kernel panic 2025-08-27 22:45:41 -07:00
fs proc: fix missing pde_set_flags() for net proc files 2025-08-27 22:45:44 -07:00
include mm: introduce and use {pgd,p4d}_populate_kernel() 2025-08-27 22:45:44 -07:00
init Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
io_uring io_uring: clear ->async_data as part of normal init 2025-08-21 13:54:01 -06:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel - Fix a case where the events throttling logic operates on inactive events 2025-08-24 10:13:05 -04:00
lib Crypto library fixes for v6.17-rc3 2025-08-21 04:54:01 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm: introduce and use {pgd,p4d}_populate_kernel() 2025-08-27 22:45:44 -07:00
net netfilter: nf_reject: don't leak dst refcount for loopback packets 2025-08-21 10:02:00 -07:00
rust rust: mm: mark VmaNew as transparent 2025-08-27 22:45:41 -07:00
samples Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
scripts kasan: fix GCC mem-intrinsic prefix with sw tags 2025-08-27 22:45:43 -07:00
security + Features 2025-08-04 08:17:28 -07:00
sound ALSA: usb-audio: Use correct sub-type for UAC3 feature unit validation 2025-08-21 17:10:14 +02:00
tools selftests/mm: fix FORCE_READ to read input value correctly 2025-08-27 22:45:42 -07:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge tag 'kvm-x86-no_assignment-6.17' of https://github.com/kvm-x86/linux into HEAD 2025-07-29 08:36:42 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore gitignore: allow .pylintrc to be tracked 2025-07-02 17:10:04 -06:00
.mailmap .mailmap: add entry for Easwar Hariharan 2025-08-19 16:35:55 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS Kbuild updates for v6.17 2025-08-06 07:32:52 +03:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS i2c-for-6.17-rc3 2025-08-24 10:32:04 -04:00
Makefile Linux 6.17-rc3 2025-08-24 12:04:12 -04:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.