powerpc/mm: Dump linux pagetables
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>
This commit is contained in:
Rashmica Gupta
Michael Ellerman
parent
8f272a5dd6
commit
8eb07b1870
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@ -354,4 +354,16 @@ config FAIL_IOMMU
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If you are unsure, say N.
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config PPC_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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This option exports the state of the kernel pagetables to a
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debugfs file. This is only useful for kernel developers who are
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working in architecture specific areas of the kernel - probably
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not a good idea to enable this feature in a production kernel.
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If you are unsure, say N.
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endmenu
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@ -42,3 +42,4 @@ obj-$(CONFIG_NOT_COHERENT_CACHE) += dma-noncoherent.o
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obj-$(CONFIG_HIGHMEM) += highmem.o
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obj-$(CONFIG_PPC_COPRO_BASE) += copro_fault.o
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obj-$(CONFIG_SPAPR_TCE_IOMMU) += mmu_context_iommu.o
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obj-$(CONFIG_PPC_PTDUMP) += dump_linuxpagetables.o
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@ -0,0 +1,440 @@
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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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* 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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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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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);
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