From: Steven Price <steven.price@arm.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
akpm@linux-foundation.org
Cc: linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-riscv@lists.infradead.org, x86@kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH v1 3/5] mm: ptdump: Provide page size to notepage()
Date: Fri, 16 Apr 2021 10:28:56 +0100 [thread overview]
Message-ID: <41819925-3ee5-4771-e98b-0073e8f095cf@arm.com> (raw)
In-Reply-To: <1ef6b954fb7b0f4dfc78820f1e612d2166c13227.1618506910.git.christophe.leroy@csgroup.eu>
On 15/04/2021 18:18, Christophe Leroy wrote:
> In order to support large pages on powerpc, notepage()
> needs to know the page size of the page.
>
> Add a page_size argument to notepage().
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> arch/arm64/mm/ptdump.c | 2 +-
> arch/riscv/mm/ptdump.c | 2 +-
> arch/s390/mm/dump_pagetables.c | 3 ++-
> arch/x86/mm/dump_pagetables.c | 2 +-
> include/linux/ptdump.h | 2 +-
> mm/ptdump.c | 16 ++++++++--------
> 6 files changed, 14 insertions(+), 13 deletions(-)
>
[...]
> diff --git a/mm/ptdump.c b/mm/ptdump.c
> index da751448d0e4..61cd16afb1c8 100644
> --- a/mm/ptdump.c
> +++ b/mm/ptdump.c
> @@ -17,7 +17,7 @@ static inline int note_kasan_page_table(struct mm_walk *walk,
> {
> struct ptdump_state *st = walk->private;
>
> - st->note_page(st, addr, 4, pte_val(kasan_early_shadow_pte[0]));
> + st->note_page(st, addr, 4, pte_val(kasan_early_shadow_pte[0]), PAGE_SIZE);
I'm not completely sure what the page_size is going to be used for, but
note that KASAN presents an interesting case here. We short-cut by
detecting it's a KASAN region at a high level (PGD/P4D/PUD/PMD) and
instead of walking the tree down just call note_page() *once* but with
level==4 because we know KASAN sets up the page table like that.
However the one call actually covers a much larger region - so while
PAGE_SIZE matches the level it doesn't match the region covered. AFAICT
this will lead to odd results if you enable KASAN on powerpc.
To be honest I don't fully understand why powerpc requires the page_size
- it appears to be using it purely to find "holes" in the calls to
note_page(), but I haven't worked out why such holes would occur.
Steve
>
> walk->action = ACTION_CONTINUE;
>
> @@ -41,7 +41,7 @@ static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
> st->effective_prot(st, 0, pgd_val(val));
>
> if (pgd_leaf(val))
> - st->note_page(st, addr, 0, pgd_val(val));
> + st->note_page(st, addr, 0, pgd_val(val), PGDIR_SIZE);
>
> return 0;
> }
> @@ -62,7 +62,7 @@ static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
> st->effective_prot(st, 1, p4d_val(val));
>
> if (p4d_leaf(val))
> - st->note_page(st, addr, 1, p4d_val(val));
> + st->note_page(st, addr, 1, p4d_val(val), P4D_SIZE);
>
> return 0;
> }
> @@ -83,7 +83,7 @@ static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
> st->effective_prot(st, 2, pud_val(val));
>
> if (pud_leaf(val))
> - st->note_page(st, addr, 2, pud_val(val));
> + st->note_page(st, addr, 2, pud_val(val), PUD_SIZE);
>
> return 0;
> }
> @@ -102,7 +102,7 @@ static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
> if (st->effective_prot)
> st->effective_prot(st, 3, pmd_val(val));
> if (pmd_leaf(val))
> - st->note_page(st, addr, 3, pmd_val(val));
> + st->note_page(st, addr, 3, pmd_val(val), PMD_SIZE);
>
> return 0;
> }
> @@ -116,7 +116,7 @@ static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
> if (st->effective_prot)
> st->effective_prot(st, 4, pte_val(val));
>
> - st->note_page(st, addr, 4, pte_val(val));
> + st->note_page(st, addr, 4, pte_val(val), PAGE_SIZE);
>
> return 0;
> }
> @@ -126,7 +126,7 @@ static int ptdump_hole(unsigned long addr, unsigned long next,
> {
> struct ptdump_state *st = walk->private;
>
> - st->note_page(st, addr, depth, 0);
> + st->note_page(st, addr, depth, 0, 0);
>
> return 0;
> }
> @@ -153,5 +153,5 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd)
> mmap_read_unlock(mm);
>
> /* Flush out the last page */
> - st->note_page(st, 0, -1, 0);
> + st->note_page(st, 0, -1, 0, 0);
> }
>
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next prev parent reply other threads:[~2021-04-16 9:46 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-15 17:18 [PATCH v1 0/5] Convert powerpc to GENERIC_PTDUMP Christophe Leroy
2021-04-15 17:18 ` [PATCH v1 1/5] mm: pagewalk: Fix walk for hugepage tables Christophe Leroy
2021-04-15 22:43 ` Daniel Axtens
2021-04-16 5:48 ` Christophe Leroy
2021-04-15 17:18 ` [PATCH v1 2/5] mm: ptdump: Fix build failure Christophe Leroy
2021-04-15 17:18 ` [PATCH v1 3/5] mm: ptdump: Provide page size to notepage() Christophe Leroy
2021-04-15 23:12 ` Daniel Axtens
2021-04-16 5:19 ` Christophe Leroy
2021-04-16 9:28 ` Steven Price [this message]
2021-04-16 10:38 ` Christophe Leroy
2021-04-16 10:51 ` Steven Price
2021-04-16 11:08 ` Christophe Leroy
2021-04-16 13:00 ` Steven Price
2021-04-16 14:40 ` Christophe Leroy
2021-04-16 15:04 ` Christophe Leroy
2021-04-16 15:15 ` Christophe Leroy
2021-04-16 16:00 ` Steven Price
2021-04-19 13:14 ` Christophe Leroy
2021-04-19 14:00 ` Steven Price
2021-04-19 16:41 ` Christophe Leroy
2021-04-15 17:18 ` [PATCH v1 4/5] mm: ptdump: Support hugepd table entries Christophe Leroy
2021-04-15 23:29 ` Daniel Axtens
2021-04-16 5:25 ` Christophe Leroy
2021-04-15 17:18 ` [PATCH v1 5/5] powerpc/mm: Convert powerpc to GENERIC_PTDUMP Christophe Leroy
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