ARM: add support to dump the kernel page tables
This patch allows the kernel page tables to be dumped via a debugfs file, allowing kernel developers to check the layout of the kernel page tables and the verify the various permissions and type settings. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King
parent
6ce4eac1f6
commit
1fd15b879d
@ -2,6 +2,18 @@ menu "Kernel hacking"
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source "lib/Kconfig.debug"
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config ARM_PTDUMP
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bool "Export kernel pagetable layout to userspace via debugfs"
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depends on DEBUG_KERNEL
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select DEBUG_FS
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---help---
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Say Y here if you want to show the kernel pagetable layout in a
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debugfs file. This information is only useful for kernel developers
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who are working in architecture specific areas of the kernel.
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It is probably not a good idea to enable this feature in a production
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kernel.
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If in doubt, say "N"
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config STRICT_DEVMEM
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bool "Filter access to /dev/mem"
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depends on MMU
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@ -160,6 +160,7 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
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return (pmd_t *)pud;
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}
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#define pmd_large(pmd) (pmd_val(pmd) & 2)
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#define pmd_bad(pmd) (pmd_val(pmd) & 2)
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#define copy_pmd(pmdpd,pmdps) \
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@ -142,6 +142,7 @@
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PMD_TYPE_TABLE)
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#define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \
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PMD_TYPE_SECT)
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#define pmd_large(pmd) pmd_sect(pmd)
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#define pud_clear(pudp) \
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do { \
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@ -12,6 +12,7 @@ ifneq ($(CONFIG_MMU),y)
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obj-y += nommu.o
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endif
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obj-$(CONFIG_ARM_PTDUMP) += dump.o
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obj-$(CONFIG_MODULES) += proc-syms.o
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obj-$(CONFIG_ALIGNMENT_TRAP) += alignment.o
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345
arch/arm/mm/dump.c
Normal file
345
arch/arm/mm/dump.c
Normal file
@ -0,0 +1,345 @@
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/*
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* Debug helper to dump the current kernel pagetables of the system
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* so that we can see what the various memory ranges are set to.
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*
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* Derived from x86 implementation:
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* (C) Copyright 2008 Intel Corporation
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*
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* Author: Arjan van de Ven <arjan@linux.intel.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; version 2
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* of the License.
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*/
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#include <linux/debugfs.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/seq_file.h>
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#include <asm/fixmap.h>
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#include <asm/pgtable.h>
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struct addr_marker {
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unsigned long start_address;
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const char *name;
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};
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static struct addr_marker address_markers[] = {
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{ MODULES_VADDR, "Modules" },
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{ PAGE_OFFSET, "Kernel Mapping" },
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{ 0, "vmalloc() Area" },
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{ VMALLOC_END, "vmalloc() End" },
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{ FIXADDR_START, "Fixmap Area" },
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{ CONFIG_VECTORS_BASE, "Vectors" },
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{ CONFIG_VECTORS_BASE + PAGE_SIZE * 2, "Vectors End" },
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{ -1, NULL },
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};
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struct pg_state {
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struct seq_file *seq;
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const struct addr_marker *marker;
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unsigned long start_address;
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unsigned level;
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u64 current_prot;
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};
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struct prot_bits {
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u64 mask;
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u64 val;
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const char *set;
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const char *clear;
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};
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static const struct prot_bits pte_bits[] = {
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{
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.mask = L_PTE_USER,
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.val = L_PTE_USER,
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.set = "USR",
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.clear = " ",
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}, {
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.mask = L_PTE_RDONLY,
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.val = L_PTE_RDONLY,
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.set = "ro",
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.clear = "RW",
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}, {
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.mask = L_PTE_XN,
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.val = L_PTE_XN,
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.set = "NX",
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.clear = "x ",
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}, {
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.mask = L_PTE_SHARED,
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.val = L_PTE_SHARED,
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.set = "SHD",
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.clear = " ",
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}, {
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.mask = L_PTE_MT_MASK,
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.val = L_PTE_MT_UNCACHED,
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.set = "SO/UNCACHED",
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}, {
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.mask = L_PTE_MT_MASK,
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.val = L_PTE_MT_BUFFERABLE,
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.set = "MEM/BUFFERABLE/WC",
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}, {
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.mask = L_PTE_MT_MASK,
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.val = L_PTE_MT_WRITETHROUGH,
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.set = "MEM/CACHED/WT",
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}, {
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.mask = L_PTE_MT_MASK,
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.val = L_PTE_MT_WRITEBACK,
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.set = "MEM/CACHED/WBRA",
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#ifndef CONFIG_ARM_LPAE
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}, {
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.mask = L_PTE_MT_MASK,
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.val = L_PTE_MT_MINICACHE,
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.set = "MEM/MINICACHE",
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#endif
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}, {
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.mask = L_PTE_MT_MASK,
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.val = L_PTE_MT_WRITEALLOC,
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.set = "MEM/CACHED/WBWA",
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}, {
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.mask = L_PTE_MT_MASK,
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.val = L_PTE_MT_DEV_SHARED,
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.set = "DEV/SHARED",
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#ifndef CONFIG_ARM_LPAE
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}, {
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.mask = L_PTE_MT_MASK,
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.val = L_PTE_MT_DEV_NONSHARED,
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.set = "DEV/NONSHARED",
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#endif
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}, {
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.mask = L_PTE_MT_MASK,
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.val = L_PTE_MT_DEV_WC,
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.set = "DEV/WC",
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}, {
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.mask = L_PTE_MT_MASK,
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.val = L_PTE_MT_DEV_CACHED,
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.set = "DEV/CACHED",
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},
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};
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static const struct prot_bits section_bits[] = {
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#ifndef CONFIG_ARM_LPAE
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/* These are approximate */
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{
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.mask = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
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.val = 0,
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.set = " ro",
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}, {
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.mask = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
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.val = PMD_SECT_AP_WRITE,
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.set = " RW",
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}, {
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.mask = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
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.val = PMD_SECT_AP_READ,
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.set = "USR ro",
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}, {
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.mask = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
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.val = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
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.set = "USR RW",
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#else
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{
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.mask = PMD_SECT_USER,
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.val = PMD_SECT_USER,
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.set = "USR",
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}, {
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.mask = PMD_SECT_RDONLY,
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.val = PMD_SECT_RDONLY,
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.set = "ro",
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.clear = "RW",
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#endif
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}, {
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.mask = PMD_SECT_XN,
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.val = PMD_SECT_XN,
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.set = "NX",
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.clear = "x ",
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}, {
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.mask = PMD_SECT_S,
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.val = PMD_SECT_S,
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.set = "SHD",
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.clear = " ",
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},
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};
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struct pg_level {
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const struct prot_bits *bits;
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size_t num;
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u64 mask;
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};
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static struct pg_level pg_level[] = {
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{
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}, { /* pgd */
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}, { /* pud */
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}, { /* pmd */
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.bits = section_bits,
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.num = ARRAY_SIZE(section_bits),
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}, { /* pte */
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.bits = pte_bits,
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.num = ARRAY_SIZE(pte_bits),
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},
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};
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static void dump_prot(struct pg_state *st, const struct prot_bits *bits, size_t num)
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{
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unsigned i;
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for (i = 0; i < num; i++, bits++) {
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const char *s;
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if ((st->current_prot & bits->mask) == bits->val)
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s = bits->set;
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else
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s = bits->clear;
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if (s)
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seq_printf(st->seq, " %s", s);
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}
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}
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static void note_page(struct pg_state *st, unsigned long addr, unsigned level, u64 val)
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{
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static const char units[] = "KMGTPE";
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u64 prot = val & pg_level[level].mask;
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if (addr < USER_PGTABLES_CEILING)
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return;
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if (!st->level) {
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st->level = level;
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st->current_prot = prot;
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seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
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} else if (prot != st->current_prot || level != st->level ||
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addr >= st->marker[1].start_address) {
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const char *unit = units;
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unsigned long delta;
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if (st->current_prot) {
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seq_printf(st->seq, "0x%08lx-0x%08lx ",
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st->start_address, addr);
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delta = (addr - st->start_address) >> 10;
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while (!(delta & 1023) && unit[1]) {
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delta >>= 10;
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unit++;
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}
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seq_printf(st->seq, "%9lu%c", delta, *unit);
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if (pg_level[st->level].bits)
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dump_prot(st, pg_level[st->level].bits, pg_level[st->level].num);
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seq_printf(st->seq, "\n");
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}
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if (addr >= st->marker[1].start_address) {
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st->marker++;
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seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
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}
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st->start_address = addr;
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st->current_prot = prot;
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st->level = level;
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}
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}
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static void walk_pte(struct pg_state *st, pmd_t *pmd, unsigned long start)
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{
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pte_t *pte = pte_offset_kernel(pmd, 0);
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unsigned long addr;
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unsigned i;
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for (i = 0; i < PTRS_PER_PTE; i++, pte++) {
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addr = start + i * PAGE_SIZE;
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note_page(st, addr, 4, pte_val(*pte));
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}
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}
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static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start)
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{
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pmd_t *pmd = pmd_offset(pud, 0);
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unsigned long addr;
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unsigned i;
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for (i = 0; i < PTRS_PER_PMD; i++, pmd++) {
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addr = start + i * PMD_SIZE;
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if (pmd_none(*pmd) || pmd_large(*pmd) || !pmd_present(*pmd))
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note_page(st, addr, 3, pmd_val(*pmd));
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else
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walk_pte(st, pmd, addr);
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}
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}
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static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)
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{
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pud_t *pud = pud_offset(pgd, 0);
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unsigned long addr;
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unsigned i;
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for (i = 0; i < PTRS_PER_PUD; i++, pud++) {
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addr = start + i * PUD_SIZE;
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if (!pud_none(*pud)) {
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walk_pmd(st, pud, addr);
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} else {
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note_page(st, addr, 2, pud_val(*pud));
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}
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}
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}
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static void walk_pgd(struct seq_file *m)
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{
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pgd_t *pgd = swapper_pg_dir;
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struct pg_state st;
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unsigned long addr;
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unsigned i, pgdoff = USER_PGTABLES_CEILING / PGDIR_SIZE;
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memset(&st, 0, sizeof(st));
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st.seq = m;
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st.marker = address_markers;
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pgd += pgdoff;
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for (i = pgdoff; i < PTRS_PER_PGD; i++, pgd++) {
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addr = i * PGDIR_SIZE;
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if (!pgd_none(*pgd)) {
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walk_pud(&st, pgd, addr);
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} else {
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note_page(&st, addr, 1, pgd_val(*pgd));
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}
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}
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note_page(&st, 0, 0, 0);
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}
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static int ptdump_show(struct seq_file *m, void *v)
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{
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walk_pgd(m);
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return 0;
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}
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static int ptdump_open(struct inode *inode, struct file *file)
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{
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return single_open(file, ptdump_show, NULL);
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}
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static const struct file_operations ptdump_fops = {
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.open = ptdump_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static int ptdump_init(void)
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{
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struct dentry *pe;
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unsigned i, j;
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for (i = 0; i < ARRAY_SIZE(pg_level); i++)
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if (pg_level[i].bits)
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for (j = 0; j < pg_level[i].num; j++)
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pg_level[i].mask |= pg_level[i].bits[j].mask;
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address_markers[2].start_address = VMALLOC_START;
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pe = debugfs_create_file("kernel_page_tables", 0400, NULL, NULL,
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&ptdump_fops);
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return pe ? 0 : -ENOMEM;
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}
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__initcall(ptdump_init);
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