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[217.140.110.172]) by mx.google.com with ESMTP id h4si704888ejj.127.2019.07.22.08.43.19 for ; Mon, 22 Jul 2019 08:43:19 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of steven.price@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of steven.price@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=steven.price@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D653C1509; Mon, 22 Jul 2019 08:43:18 -0700 (PDT) Received: from e112269-lin.arm.com (e112269-lin.cambridge.arm.com [10.1.196.133]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4D1383F694; Mon, 22 Jul 2019 08:43:16 -0700 (PDT) From: Steven Price To: linux-mm@kvack.org Cc: Steven Price , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Dave Hansen , Ingo Molnar , James Morse , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Peter Zijlstra , Thomas Gleixner , Will Deacon , x86@kernel.org, "H. Peter Anvin" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Mark Rutland , "Liang, Kan" , Andrew Morton Subject: [PATCH v9 19/21] mm: Add generic ptdump Date: Mon, 22 Jul 2019 16:42:08 +0100 Message-Id: <20190722154210.42799-20-steven.price@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190722154210.42799-1-steven.price@arm.com> References: <20190722154210.42799-1-steven.price@arm.com> MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Add a generic version of page table dumping that architectures can opt-in to Signed-off-by: Steven Price --- include/linux/ptdump.h | 19 +++++ mm/Kconfig.debug | 21 ++++++ mm/Makefile | 1 + mm/ptdump.c | 161 +++++++++++++++++++++++++++++++++++++++++ 4 files changed, 202 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..eb8e78154be3 --- /dev/null +++ b/include/linux/ptdump.h @@ -0,0 +1,19 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef _LINUX_PTDUMP_H +#define _LINUX_PTDUMP_H + +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 82b6a20898bd..7ad939b7140f 100644 --- a/mm/Kconfig.debug +++ b/mm/Kconfig.debug @@ -115,3 +115,24 @@ 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 338e528ad436..750a4c12d5da 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -104,3 +104,4 @@ obj-$(CONFIG_HARDENED_USERCOPY) += usercopy.o obj-$(CONFIG_PERCPU_STATS) += percpu-stats.o obj-$(CONFIG_HMM_MIRROR) += hmm.o obj-$(CONFIG_MEMFD_CREATE) += memfd.o +obj-$(CONFIG_PTDUMP_CORE) += ptdump.o diff --git a/mm/ptdump.c b/mm/ptdump.c new file mode 100644 index 000000000000..39befc9088b8 --- /dev/null +++ b/mm/ptdump.c @@ -0,0 +1,161 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include + +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 (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 (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 (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 (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; +} + +#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 bool kasan_page_table(struct ptdump_state *st, void *pt, + unsigned long addr) +{ + if (__pa(pt) == __pa(kasan_early_shadow_pmd) || +#ifdef CONFIG_X86 + (pgtable_l5_enabled() && + __pa(pt) == __pa(kasan_early_shadow_p4d)) || +#endif + __pa(pt) == __pa(kasan_early_shadow_pud)) { + st->note_page(st, addr, 5, pte_val(kasan_early_shadow_pte[0])); + return true; + } + return false; +} +#else +static inline bool kasan_page_table(struct ptdump_state *st, void *pt, + unsigned long addr) +{ + return false; +} +#endif + +static int ptdump_test_p4d(unsigned long addr, unsigned long next, + p4d_t *p4d, struct mm_walk *walk) +{ + struct ptdump_state *st = walk->private; + + if (kasan_page_table(st, p4d, addr)) + return 1; + return 0; +} + +static int ptdump_test_pud(unsigned long addr, unsigned long next, + pud_t *pud, struct mm_walk *walk) +{ + struct ptdump_state *st = walk->private; + + if (kasan_page_table(st, pud, addr)) + return 1; + return 0; +} + +static int ptdump_test_pmd(unsigned long addr, unsigned long next, + pmd_t *pmd, struct mm_walk *walk) +{ + struct ptdump_state *st = walk->private; + + if (kasan_page_table(st, pmd, addr)) + return 1; + return 0; +} + +static int ptdump_hole(unsigned long addr, unsigned long next, + struct mm_walk *walk) +{ + struct ptdump_state *st = walk->private; + + st->note_page(st, addr, -1, 0); + + return 0; +} + +void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm) +{ + struct mm_walk walk = { + .mm = mm, + .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, + .test_p4d = ptdump_test_p4d, + .test_pud = ptdump_test_pud, + .test_pmd = ptdump_test_pmd, + .pte_hole = ptdump_hole, + .private = st + }; + const struct ptdump_range *range = st->range; + + down_read(&mm->mmap_sem); + while (range->start != range->end) { + walk_page_range(range->start, range->end, &walk); + range++; + } + up_read(&mm->mmap_sem); + + /* Flush out the last page */ + st->note_page(st, 0, 0, 0); +}