430 lines
11 KiB
C
430 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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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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#include <linux/debugfs.h>
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#include <linux/fs.h>
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#include <linux/hugetlb.h>
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#include <linux/io.h>
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#include <linux/mm.h>
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#include <linux/highmem.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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#include "ptdump.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 long start_pa;
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unsigned long last_pa;
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unsigned long page_size;
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unsigned int level;
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u64 current_flags;
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bool check_wx;
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unsigned long wx_pages;
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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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#ifdef CONFIG_PPC64
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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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#else
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{ 0, "Early I/O remap start" },
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{ 0, "Early I/O remap end" },
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#ifdef CONFIG_HIGHMEM
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{ 0, "Highmem PTEs start" },
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{ 0, "Highmem PTEs end" },
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#endif
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{ 0, "Fixmap start" },
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{ 0, "Fixmap end" },
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#endif
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#ifdef CONFIG_KASAN
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{ 0, "kasan shadow mem start" },
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{ 0, "kasan shadow mem end" },
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#endif
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{ -1, NULL },
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};
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#define pt_dump_seq_printf(m, fmt, args...) \
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({ \
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if (m) \
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seq_printf(m, fmt, ##args); \
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})
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#define pt_dump_seq_putc(m, c) \
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({ \
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if (m) \
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seq_putc(m, c); \
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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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pt_dump_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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pt_dump_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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pt_dump_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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#ifdef CONFIG_PPC64
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#define REG "0x%016lx"
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#else
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#define REG "0x%08lx"
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#endif
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pt_dump_seq_printf(st->seq, REG "-" REG " ", st->start_address, addr - 1);
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if (st->start_pa == st->last_pa && st->start_address + st->page_size != addr) {
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pt_dump_seq_printf(st->seq, "[" REG "]", st->start_pa);
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delta = st->page_size >> 10;
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} else {
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pt_dump_seq_printf(st->seq, " " REG " ", st->start_pa);
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delta = (addr - st->start_address) >> 10;
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}
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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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pt_dump_seq_printf(st->seq, "%9lu%c", delta, *unit);
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}
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static void note_prot_wx(struct pg_state *st, unsigned long addr)
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{
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pte_t pte = __pte(st->current_flags);
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if (!IS_ENABLED(CONFIG_PPC_DEBUG_WX) || !st->check_wx)
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return;
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if (!pte_write(pte) || !pte_exec(pte))
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return;
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WARN_ONCE(1, "powerpc/mm: Found insecure W+X mapping at address %p/%pS\n",
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(void *)st->start_address, (void *)st->start_address);
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st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
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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, unsigned long page_size)
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{
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u64 flag = val & pg_level[level].mask;
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u64 pa = val & PTE_RPN_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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st->start_pa = pa;
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st->last_pa = pa;
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st->page_size = page_size;
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pt_dump_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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* - the pa of this page is not adjacent to the last inspected page
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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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(pa != st->last_pa + st->page_size &&
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(pa != st->start_pa || st->start_pa != st->last_pa))) {
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/* Check the PTE flags */
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if (st->current_flags) {
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note_prot_wx(st, addr);
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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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pt_dump_seq_putc(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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pt_dump_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->start_pa = pa;
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st->last_pa = pa;
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st->page_size = page_size;
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st->current_flags = flag;
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st->level = level;
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} else {
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st->last_pa = pa;
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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), PAGE_SIZE);
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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) && !pmd_is_leaf(*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), PMD_SIZE);
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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) && !pud_is_leaf(*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), PUD_SIZE);
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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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unsigned int i;
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unsigned long addr = st->start_address & PGDIR_MASK;
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pgd_t *pgd = pgd_offset_k(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 = pgd_index(addr); i < PTRS_PER_PGD; i++, pgd++, addr += PGDIR_SIZE) {
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if (!pgd_none(*pgd) && !pgd_is_leaf(*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), PGDIR_SIZE);
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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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int i = 0;
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address_markers[i++].start_address = PAGE_OFFSET;
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address_markers[i++].start_address = VMALLOC_START;
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address_markers[i++].start_address = VMALLOC_END;
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#ifdef CONFIG_PPC64
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address_markers[i++].start_address = ISA_IO_BASE;
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address_markers[i++].start_address = ISA_IO_END;
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address_markers[i++].start_address = PHB_IO_BASE;
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address_markers[i++].start_address = PHB_IO_END;
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address_markers[i++].start_address = IOREMAP_BASE;
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address_markers[i++].start_address = IOREMAP_END;
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/* What is the ifdef about? */
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#ifdef CONFIG_PPC_BOOK3S_64
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address_markers[i++].start_address = H_VMEMMAP_START;
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#else
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address_markers[i++].start_address = VMEMMAP_BASE;
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#endif
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#else /* !CONFIG_PPC64 */
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address_markers[i++].start_address = ioremap_bot;
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address_markers[i++].start_address = IOREMAP_TOP;
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#ifdef CONFIG_HIGHMEM
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address_markers[i++].start_address = PKMAP_BASE;
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address_markers[i++].start_address = PKMAP_ADDR(LAST_PKMAP);
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#endif
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address_markers[i++].start_address = FIXADDR_START;
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address_markers[i++].start_address = FIXADDR_TOP;
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#ifdef CONFIG_KASAN
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address_markers[i++].start_address = KASAN_SHADOW_START;
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address_markers[i++].start_address = KASAN_SHADOW_END;
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#endif
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#endif /* CONFIG_PPC64 */
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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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.marker = address_markers,
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.start_address = PAGE_OFFSET,
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};
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#ifdef CONFIG_PPC64
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if (!radix_enabled())
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st.start_address = KERN_VIRT_START;
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#endif
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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, 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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#ifdef CONFIG_PPC_DEBUG_WX
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void ptdump_check_wx(void)
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{
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struct pg_state st = {
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.seq = NULL,
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.marker = address_markers,
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.check_wx = true,
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.start_address = PAGE_OFFSET,
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};
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#ifdef CONFIG_PPC64
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if (!radix_enabled())
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st.start_address = KERN_VIRT_START;
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#endif
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walk_pagetables(&st);
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if (st.wx_pages)
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pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n",
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st.wx_pages);
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else
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pr_info("Checked W+X mappings: passed, no W+X pages found\n");
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}
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#endif
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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_page_tables", 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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