From 30d621f6723b1c98a142861f7a52849d286bc7fa Mon Sep 17 00:00:00 2001 From: Steven Price Date: Mon, 3 Feb 2020 17:36:20 -0800 Subject: [PATCH] mm: add generic ptdump Add a generic version of page table dumping that architectures can opt-in to. Link: http://lkml.kernel.org/r/20191218162402.45610-20-steven.price@arm.com Signed-off-by: Steven Price Cc: Albert Ou Cc: Alexandre Ghiti Cc: Andy Lutomirski Cc: Ard Biesheuvel Cc: Arnd Bergmann Cc: Benjamin Herrenschmidt Cc: Borislav Petkov Cc: Catalin Marinas Cc: Christian Borntraeger Cc: Dave Hansen Cc: David S. Miller Cc: Heiko Carstens Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: James Hogan Cc: James Morse Cc: Jerome Glisse Cc: "Liang, Kan" Cc: Mark Rutland Cc: Michael Ellerman Cc: Paul Burton Cc: Paul Mackerras Cc: Paul Walmsley Cc: Peter Zijlstra Cc: Ralf Baechle Cc: Russell King Cc: Thomas Gleixner Cc: Vasily Gorbik Cc: Vineet Gupta Cc: Will Deacon Cc: Zong Li Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/ptdump.h | 21 +++++++ mm/Kconfig.debug | 21 +++++++ mm/Makefile | 1 + mm/ptdump.c | 139 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 182 insertions(+) create mode 100644 include/linux/ptdump.h create mode 100644 mm/ptdump.c diff --git a/include/linux/ptdump.h b/include/linux/ptdump.h new file mode 100644 index 000000000000..a0fb8dd2be97 --- /dev/null +++ b/include/linux/ptdump.h @@ -0,0 +1,21 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef _LINUX_PTDUMP_H +#define _LINUX_PTDUMP_H + +#include + +struct ptdump_range { + unsigned long start; + unsigned long end; +}; + +struct ptdump_state { + void (*note_page)(struct ptdump_state *st, unsigned long addr, + int level, unsigned long val); + const struct ptdump_range *range; +}; + +void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm); + +#endif /* _LINUX_PTDUMP_H */ diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug index 327b3ebf23bf..0271b22e063f 100644 --- a/mm/Kconfig.debug +++ b/mm/Kconfig.debug @@ -117,3 +117,24 @@ config DEBUG_RODATA_TEST depends on STRICT_KERNEL_RWX ---help--- This option enables a testcase for the setting rodata read-only. + +config GENERIC_PTDUMP + bool + +config PTDUMP_CORE + bool + +config PTDUMP_DEBUGFS + bool "Export kernel pagetable layout to userspace via debugfs" + depends on DEBUG_KERNEL + depends on DEBUG_FS + depends on GENERIC_PTDUMP + select PTDUMP_CORE + help + Say Y here if you want to show the kernel pagetable layout in a + debugfs file. This information is only useful for kernel developers + who are working in architecture specific areas of the kernel. + It is probably not a good idea to enable this feature in a production + kernel. + + If in doubt, say N. diff --git a/mm/Makefile b/mm/Makefile index 32f08e22e824..272e66039e70 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -109,3 +109,4 @@ obj-$(CONFIG_ZONE_DEVICE) += memremap.o obj-$(CONFIG_HMM_MIRROR) += hmm.o obj-$(CONFIG_MEMFD_CREATE) += memfd.o obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o +obj-$(CONFIG_PTDUMP_CORE) += ptdump.o diff --git a/mm/ptdump.c b/mm/ptdump.c new file mode 100644 index 000000000000..868638b8e404 --- /dev/null +++ b/mm/ptdump.c @@ -0,0 +1,139 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include + +#ifdef CONFIG_KASAN +/* + * This is an optimization for KASAN=y case. Since all kasan page tables + * eventually point to the kasan_early_shadow_page we could call note_page() + * right away without walking through lower level page tables. This saves + * us dozens of seconds (minutes for 5-level config) while checking for + * W+X mapping or reading kernel_page_tables debugfs file. + */ +static inline int note_kasan_page_table(struct mm_walk *walk, + unsigned long addr) +{ + struct ptdump_state *st = walk->private; + + st->note_page(st, addr, 5, pte_val(kasan_early_shadow_pte[0])); + + walk->action = ACTION_CONTINUE; + + return 0; +} +#endif + +static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr, + unsigned long next, struct mm_walk *walk) +{ + struct ptdump_state *st = walk->private; + pgd_t val = READ_ONCE(*pgd); + +#if CONFIG_PGTABLE_LEVELS > 4 && defined(CONFIG_KASAN) + if (pgd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_p4d))) + return note_kasan_page_table(walk, addr); +#endif + + if (pgd_leaf(val)) + st->note_page(st, addr, 1, pgd_val(val)); + + return 0; +} + +static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr, + unsigned long next, struct mm_walk *walk) +{ + struct ptdump_state *st = walk->private; + p4d_t val = READ_ONCE(*p4d); + +#if CONFIG_PGTABLE_LEVELS > 3 && defined(CONFIG_KASAN) + if (p4d_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pud))) + return note_kasan_page_table(walk, addr); +#endif + + if (p4d_leaf(val)) + st->note_page(st, addr, 2, p4d_val(val)); + + return 0; +} + +static int ptdump_pud_entry(pud_t *pud, unsigned long addr, + unsigned long next, struct mm_walk *walk) +{ + struct ptdump_state *st = walk->private; + pud_t val = READ_ONCE(*pud); + +#if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_KASAN) + if (pud_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pmd))) + return note_kasan_page_table(walk, addr); +#endif + + if (pud_leaf(val)) + st->note_page(st, addr, 3, pud_val(val)); + + return 0; +} + +static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr, + unsigned long next, struct mm_walk *walk) +{ + struct ptdump_state *st = walk->private; + pmd_t val = READ_ONCE(*pmd); + +#if defined(CONFIG_KASAN) + if (pmd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pte))) + return note_kasan_page_table(walk, addr); +#endif + + if (pmd_leaf(val)) + st->note_page(st, addr, 4, pmd_val(val)); + + return 0; +} + +static int ptdump_pte_entry(pte_t *pte, unsigned long addr, + unsigned long next, struct mm_walk *walk) +{ + struct ptdump_state *st = walk->private; + + st->note_page(st, addr, 5, pte_val(READ_ONCE(*pte))); + + return 0; +} + +static int ptdump_hole(unsigned long addr, unsigned long next, + int depth, struct mm_walk *walk) +{ + struct ptdump_state *st = walk->private; + + st->note_page(st, addr, depth + 1, 0); + + return 0; +} + +static const struct mm_walk_ops ptdump_ops = { + .pgd_entry = ptdump_pgd_entry, + .p4d_entry = ptdump_p4d_entry, + .pud_entry = ptdump_pud_entry, + .pmd_entry = ptdump_pmd_entry, + .pte_entry = ptdump_pte_entry, + .pte_hole = ptdump_hole, +}; + +void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm) +{ + const struct ptdump_range *range = st->range; + + down_read(&mm->mmap_sem); + while (range->start != range->end) { + walk_page_range_novma(mm, range->start, range->end, + &ptdump_ops, st); + range++; + } + up_read(&mm->mmap_sem); + + /* Flush out the last page */ + st->note_page(st, 0, 0, 0); +}