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authorRyan Roberts <ryan.roberts@arm.com>2023-06-12 17:15:43 +0200
committerAndrew Morton <akpm@linux-foundation.org>2023-06-20 01:19:24 +0200
commit426931e7e5d96664616794c7c36efc748a7497e2 (patch)
treec80d0d4699f29626e1d5959f5ceb2867202d9f67
parentsh: move the ARCH_DMA_MINALIGN definition to asm/cache.h (diff)
downloadlinux-426931e7e5d96664616794c7c36efc748a7497e2.tar.xz
linux-426931e7e5d96664616794c7c36efc748a7497e2.zip
mm: ptdump should use ptep_get_lockless()
Patch series "Encapsulate PTE contents from non-arch code", v3. A series to improve the encapsulation of pte entries by disallowing non-arch code from directly dereferencing pte_t pointers. This means that by default, the accesses change from a C dereference to a READ_ONCE(). This is technically the correct thing to do since where pgtables are modified by HW (for access/dirty) they are volatile and therefore we should always ensure READ_ONCE() semantics. But more importantly, by always using the helper, it can be overridden by the architecture to fully encapsulate the contents of the pte. Arch code is deliberately not converted, as the arch code knows best. It is intended that arch code (arm64) will override the default with its own implementation that can (e.g.) hide certain bits from the core code, or determine young/dirty status by mixing in state from another source. This patch (of 3): The page table dumper uses walk_page_range_novma() to walk the page tables, which does not lock the PTL before calling the pte_entry() callback. Therefore, the page table dumper's callback must use ptep_get_lockless() rather than ptep_get() to ensure that the pte it reads is not torn or otherwise corrupt when racing with writers. Link: https://lkml.kernel.org/r/20230612151545.3317766-1-ryan.roberts@arm.com Link: https://lkml.kernel.org/r/20230612151545.3317766-2-ryan.roberts@arm.com Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Potapenko <glider@google.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Dave Airlie <airlied@gmail.com> Cc: Dimitri Sivanich <dimitri.sivanich@hpe.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Ian Rogers <irogers@google.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport (IBM) <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Naoya Horiguchi <naoya.horiguchi@nec.com> Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: SeongJae Park <sj@kernel.org> Cc: Shakeel Butt <shakeelb@google.com> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Yu Zhao <yuzhao@google.com> Cc: kernel test robot <lkp@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--mm/ptdump.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/ptdump.c b/mm/ptdump.c
index 8adab455a68b..03c1bdae4a43 100644
--- a/mm/ptdump.c
+++ b/mm/ptdump.c
@@ -119,7 +119,7 @@ static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
unsigned long next, struct mm_walk *walk)
{
struct ptdump_state *st = walk->private;
- pte_t val = ptep_get(pte);
+ pte_t val = ptep_get_lockless(pte);
if (st->effective_prot)
st->effective_prot(st, 4, pte_val(val));