Useful to be able to dump the kernels page tables to check permissions and memory types - derived from arm64's implementation. Add a debugfs file to check the page tables. To use this the PPC_PTDUMP config option must be selected. Signed-off-by: Rashmica Gupta <rashmicy@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>tirimbino
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/*
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* Copyright 2016, Rashmica Gupta, IBM Corp. |
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* |
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* This traverses the kernel pagetables and dumps the |
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* information about the used sections of memory to |
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* /sys/kernel/debug/kernel_pagetables. |
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* |
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* Derived from the arm64 implementation: |
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* Copyright (c) 2014, The Linux Foundation, Laura Abbott. |
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* (C) Copyright 2008 Intel Corporation, Arjan van de Ven. |
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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/io.h> |
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#include <linux/mm.h> |
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#include <linux/sched.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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#include <linux/const.h> |
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#include <asm/page.h> |
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#include <asm/pgalloc.h> |
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|
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/*
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* To visualise what is happening, |
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* |
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* - PTRS_PER_P** = how many entries there are in the corresponding P** |
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* - P**_SHIFT = how many bits of the address we use to index into the |
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* corresponding P** |
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* - P**_SIZE is how much memory we can access through the table - not the |
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* size of the table itself. |
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* P**={PGD, PUD, PMD, PTE} |
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* |
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* |
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* Each entry of the PGD points to a PUD. Each entry of a PUD points to a |
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* PMD. Each entry of a PMD points to a PTE. And every PTE entry points to |
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* a page. |
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* |
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* In the case where there are only 3 levels, the PUD is folded into the |
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* PGD: every PUD has only one entry which points to the PMD. |
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* |
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* The page dumper groups page table entries of the same type into a single |
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* description. It uses pg_state to track the range information while |
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* iterating over the PTE entries. When the continuity is broken it then |
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* dumps out a description of the range - ie PTEs that are virtually contiguous |
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* with the same PTE flags are chunked together. This is to make it clear how |
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* different areas of the kernel virtual memory are used. |
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* |
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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 int level; |
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u64 current_flags; |
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}; |
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|
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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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{ 0, "Start of kernel VM" }, |
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{ 0, "vmalloc() Area" }, |
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{ 0, "vmalloc() End" }, |
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{ 0, "isa I/O start" }, |
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{ 0, "isa I/O end" }, |
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{ 0, "phb I/O start" }, |
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{ 0, "phb I/O end" }, |
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{ 0, "I/O remap start" }, |
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{ 0, "I/O remap end" }, |
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{ 0, "vmemmap start" }, |
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{ -1, NULL }, |
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}; |
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|
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struct flag_info { |
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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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bool is_val; |
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int shift; |
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}; |
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static const struct flag_info flag_array[] = { |
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{ |
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#ifdef CONFIG_PPC_STD_MMU_64 |
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.mask = _PAGE_PRIVILEGED, |
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.val = 0, |
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#else |
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.mask = _PAGE_USER, |
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.val = _PAGE_USER, |
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#endif |
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.set = "user", |
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.clear = " ", |
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}, { |
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.mask = _PAGE_RW, |
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.val = _PAGE_RW, |
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.set = "rw", |
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.clear = "ro", |
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}, { |
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.mask = _PAGE_EXEC, |
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.val = _PAGE_EXEC, |
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.set = " X ", |
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.clear = " ", |
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}, { |
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.mask = _PAGE_PTE, |
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.val = _PAGE_PTE, |
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.set = "pte", |
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.clear = " ", |
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}, { |
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.mask = _PAGE_PRESENT, |
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.val = _PAGE_PRESENT, |
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.set = "present", |
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.clear = " ", |
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}, { |
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#ifdef CONFIG_PPC_STD_MMU_64 |
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.mask = H_PAGE_HASHPTE, |
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.val = H_PAGE_HASHPTE, |
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#else |
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.mask = _PAGE_HASHPTE, |
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.val = _PAGE_HASHPTE, |
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#endif |
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.set = "hpte", |
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.clear = " ", |
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}, { |
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#ifndef CONFIG_PPC_STD_MMU_64 |
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.mask = _PAGE_GUARDED, |
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.val = _PAGE_GUARDED, |
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.set = "guarded", |
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.clear = " ", |
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}, { |
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#endif |
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.mask = _PAGE_DIRTY, |
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.val = _PAGE_DIRTY, |
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.set = "dirty", |
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.clear = " ", |
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}, { |
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.mask = _PAGE_ACCESSED, |
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.val = _PAGE_ACCESSED, |
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.set = "accessed", |
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.clear = " ", |
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}, { |
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#ifndef CONFIG_PPC_STD_MMU_64 |
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.mask = _PAGE_WRITETHRU, |
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.val = _PAGE_WRITETHRU, |
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.set = "write through", |
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.clear = " ", |
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}, { |
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#endif |
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.mask = _PAGE_NO_CACHE, |
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.val = _PAGE_NO_CACHE, |
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.set = "no cache", |
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.clear = " ", |
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}, { |
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.mask = H_PAGE_BUSY, |
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.val = H_PAGE_BUSY, |
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.set = "busy", |
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}, { |
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#ifdef CONFIG_PPC_64K_PAGES |
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.mask = H_PAGE_COMBO, |
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.val = H_PAGE_COMBO, |
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.set = "combo", |
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}, { |
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.mask = H_PAGE_4K_PFN, |
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.val = H_PAGE_4K_PFN, |
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.set = "4K_pfn", |
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}, { |
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#endif |
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.mask = H_PAGE_F_GIX, |
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.val = H_PAGE_F_GIX, |
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.set = "f_gix", |
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.is_val = true, |
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.shift = H_PAGE_F_GIX_SHIFT, |
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}, { |
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.mask = H_PAGE_F_SECOND, |
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.val = H_PAGE_F_SECOND, |
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.set = "f_second", |
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}, { |
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.mask = _PAGE_SPECIAL, |
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.val = _PAGE_SPECIAL, |
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.set = "special", |
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} |
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}; |
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struct pgtable_level { |
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const struct flag_info *flag; |
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size_t num; |
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u64 mask; |
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}; |
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static struct pgtable_level pg_level[] = { |
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{ |
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}, { /* pgd */ |
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.flag = flag_array, |
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.num = ARRAY_SIZE(flag_array), |
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}, { /* pud */ |
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.flag = flag_array, |
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.num = ARRAY_SIZE(flag_array), |
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}, { /* pmd */ |
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.flag = flag_array, |
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.num = ARRAY_SIZE(flag_array), |
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}, { /* pte */ |
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.flag = flag_array, |
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.num = ARRAY_SIZE(flag_array), |
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}, |
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}; |
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static void dump_flag_info(struct pg_state *st, const struct flag_info |
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*flag, u64 pte, int num) |
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{ |
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unsigned int i; |
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for (i = 0; i < num; i++, flag++) { |
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const char *s = NULL; |
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u64 val; |
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/* flag not defined so don't check it */ |
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if (flag->mask == 0) |
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continue; |
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/* Some 'flags' are actually values */ |
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if (flag->is_val) { |
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val = pte & flag->val; |
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if (flag->shift) |
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val = val >> flag->shift; |
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seq_printf(st->seq, " %s:%llx", flag->set, val); |
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} else { |
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if ((pte & flag->mask) == flag->val) |
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s = flag->set; |
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else |
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s = flag->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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st->current_flags &= ~flag->mask; |
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} |
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if (st->current_flags != 0) |
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seq_printf(st->seq, " unknown flags:%llx", st->current_flags); |
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} |
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static void dump_addr(struct pg_state *st, unsigned long addr) |
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{ |
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static const char units[] = "KMGTPE"; |
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const char *unit = units; |
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unsigned long delta; |
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seq_printf(st->seq, "0x%016lx-0x%016lx ", st->start_address, addr-1); |
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delta = (addr - st->start_address) >> 10; |
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/* Work out what appropriate unit to use */ |
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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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} |
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static void note_page(struct pg_state *st, unsigned long addr, |
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unsigned int level, u64 val) |
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{ |
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u64 flag = val & pg_level[level].mask; |
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/* At first no level is set */ |
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if (!st->level) { |
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st->level = level; |
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st->current_flags = flag; |
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st->start_address = addr; |
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seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); |
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/*
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* Dump the section of virtual memory when: |
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* - the PTE flags from one entry to the next differs. |
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* - we change levels in the tree. |
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* - the address is in a different section of memory and is thus |
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* used for a different purpose, regardless of the flags. |
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*/ |
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} else if (flag != st->current_flags || level != st->level || |
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addr >= st->marker[1].start_address) { |
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/* Check the PTE flags */ |
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if (st->current_flags) { |
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dump_addr(st, addr); |
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/* Dump all the flags */ |
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if (pg_level[st->level].flag) |
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dump_flag_info(st, pg_level[st->level].flag, |
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st->current_flags, |
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pg_level[st->level].num); |
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seq_puts(st->seq, "\n"); |
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} |
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/*
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* Address indicates we have passed the end of the |
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* current section of virtual memory |
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*/ |
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while (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_flags = flag; |
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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 int 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 int 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)) |
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/* pmd exists */ |
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walk_pte(st, pmd, addr); |
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else |
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note_page(st, addr, 3, pmd_val(*pmd)); |
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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 int 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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/* pud exists */ |
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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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static void walk_pagetables(struct pg_state *st) |
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{ |
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pgd_t *pgd = pgd_offset_k(0UL); |
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unsigned int i; |
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unsigned long addr; |
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/*
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* Traverse the linux pagetable structure and dump pages that are in |
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* the hash pagetable. |
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*/ |
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for (i = 0; i < PTRS_PER_PGD; i++, pgd++) { |
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addr = KERN_VIRT_START + i * PGDIR_SIZE; |
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if (!pgd_none(*pgd)) |
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/* pgd exists */ |
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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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static void populate_markers(void) |
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{ |
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address_markers[0].start_address = PAGE_OFFSET; |
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address_markers[1].start_address = VMALLOC_START; |
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address_markers[2].start_address = VMALLOC_END; |
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address_markers[3].start_address = ISA_IO_BASE; |
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address_markers[4].start_address = ISA_IO_END; |
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address_markers[5].start_address = PHB_IO_BASE; |
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address_markers[6].start_address = PHB_IO_END; |
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address_markers[7].start_address = IOREMAP_BASE; |
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address_markers[8].start_address = IOREMAP_END; |
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#ifdef CONFIG_PPC_STD_MMU_64 |
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address_markers[9].start_address = H_VMEMMAP_BASE; |
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#else |
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address_markers[9].start_address = VMEMMAP_BASE; |
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#endif |
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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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struct pg_state st = { |
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.seq = m, |
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.start_address = KERN_VIRT_START, |
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.marker = address_markers, |
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}; |
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/* Traverse kernel page tables */ |
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walk_pagetables(&st); |
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note_page(&st, 0, 0, 0); |
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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 void build_pgtable_complete_mask(void) |
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{ |
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unsigned int i, j; |
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for (i = 0; i < ARRAY_SIZE(pg_level); i++) |
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if (pg_level[i].flag) |
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for (j = 0; j < pg_level[i].num; j++) |
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pg_level[i].mask |= pg_level[i].flag[j].mask; |
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} |
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static int ptdump_init(void) |
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{ |
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struct dentry *debugfs_file; |
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populate_markers(); |
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build_pgtable_complete_mask(); |
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debugfs_file = debugfs_create_file("kernel_pagetables", 0400, NULL, |
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NULL, &ptdump_fops); |
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return debugfs_file ? 0 : -ENOMEM; |
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} |
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device_initcall(ptdump_init); |
Loading…
Reference in new issue