Re: [PATCH v1 3/5] mm: ptdump: Provide page size to notepage()
From: Steven Price <steven.price@arm.com>
Date: 2021-04-16 09:29:07
Also in:
linux-arch, linux-arm-kernel, linux-mm, linux-riscv, linux-s390, lkml
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 <redacted> --- 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(-)
[...]
quoted hunk ↗ jump to hunk
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
quoted hunk ↗ jump to hunk
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); }