// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright 2016, Rashmica Gupta, IBM Corp.
*
* This traverses the kernel pagetables and dumps the
* information about the used sections of memory to
* /sys/kernel/debug/kernel_pagetables.
*
* Derived from the arm64 implementation:
* Copyright (c) 2014, The Linux Foundation, Laura Abbott.
* (C) Copyright 2008 Intel Corporation, Arjan van de Ven.
*/
#include <linux/debugfs.h>
#include <linux/fs.h>
#include <linux/hugetlb.h>
#include <linux/io.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/ptdump.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <asm/fixmap.h>
#include <linux/const.h>
#include <linux/kasan.h>
#include <asm/page.h>
#include <asm/hugetlb.h>
#include <mm/mmu_decl.h>
#include "ptdump.h"
/*
* To visualise what is happening,
*
* - PTRS_PER_P** = how many entries there are in the corresponding P**
* - P**_SHIFT = how many bits of the address we use to index into the
* corresponding P**
* - P**_SIZE is how much memory we can access through the table - not the
* size of the table itself.
* P**={PGD, PUD, PMD, PTE}
*
*
* Each entry of the PGD points to a PUD. Each entry of a PUD points to a
* PMD. Each entry of a PMD points to a PTE. And every PTE entry points to
* a page.
*
* In the case where there are only 3 levels, the PUD is folded into the
* PGD: every PUD has only one entry which points to the PMD.
*
* The page dumper groups page table entries of the same type into a single
* description. It uses pg_state to track the range information while
* iterating over the PTE entries. When the continuity is broken it then
* dumps out a description of the range - ie PTEs that are virtually contiguous
* with the same PTE flags are chunked together. This is to make it clear how
* different areas of the kernel virtual memory are used.
*
*/
struct pg_state {
struct ptdump_state ptdump;
struct seq_file *seq;
const struct addr_marker *marker;
unsigned long start_address;
unsigned long start_pa;
int level;
u64 current_flags;
bool check_wx;
unsigned long wx_pages;
};
struct addr_marker {
unsigned long start_address;
const char *name;
};
static struct addr_marker address_markers[] = {
{ 0, "Start of kernel VM" },
#ifdef MODULES_VADDR
{ 0, "modules start" },
{ 0, "modules end" },
#endif
{ 0, "vmalloc() Area" },
{ 0, "vmalloc() End" },
#ifdef CONFIG_PPC64
{ 0, "isa I/O start" },
{ 0, "isa I/O end" },
{ 0, "phb I/O start" },
{ 0, "phb I/O end" },
{ 0, "I/O remap start" },
{ 0, "I/O remap end" },
{ 0, "vmemmap start" },
#else
{ 0, "Early I/O remap start" },
{ 0, "Early I/O remap end" },
#ifdef CONFIG_HIGHMEM
{ 0, "Highmem PTEs start" },
{ 0, "Highmem PTEs end" },
#endif
{ 0, "Fixmap start" },
{ 0, "Fixmap end" },
#endif
#ifdef CONFIG_KASAN
{ 0, "kasan shadow mem start" },
{ 0, "kasan shadow mem end" },
#endif
{ -1, NULL },
};
static struct ptdump_range ptdump_range[] __ro_after_init = {
{TASK_SIZE_MAX, ~0UL},
{0, 0}
};
#define pt_dump_seq_printf(m, fmt, args...) \
({ \
if (m) \
seq_printf(m, fmt, ##args); \
})
#define pt_dump_seq_putc(m, c) \
({ \
if (m) \
seq_putc(m, c); \
})
void pt_dump_size(struct seq_file *m, unsigned long size)
{
static const char units[] = " KMGTPE";
const char *unit = units;
/* Work out what appropriate unit to use */
while (!(size & 1023) && unit[1]) {
size >>= 10;
unit++;
}
pt_dump_seq_printf(m, "%9lu%c ", size, *unit);
}
static void dump_flag_info(struct pg_state *st, const struct flag_info
*flag, u64 pte, int num)
{
unsigned int i;
for (i = 0; i < num; i++, flag++) {
const char *s = NULL;
u64 val;
/* flag not defined so don't check it */
if (flag->mask == 0)
continue;
/* Some 'flags' are actually values */
if (flag->is_val) {
val = pte & flag->val;
if (flag->shift)
val = val >> flag->shift;
pt_dump_seq_printf(st->seq, " %s:%llx", flag->set, val);
} else {
if ((pte & flag->mask) == flag->val)
s = flag->set;
else
s = flag->clear;
if (s)
pt_dump_seq_printf(st->seq, " %s", s);
}
st->current_flags &= ~flag->mask;
}
if (st->current_flags != 0)
pt_dump_seq_printf(st->seq, " unknown flags:%llx", st->current_flags);
}
static void dump_addr(struct pg_state *st, unsigned long addr)
{
#ifdef CONFIG_PPC64
#define REG "0x%016lx"
#else
#define REG "0x%08lx"
#endif
pt_dump_seq_printf(st->seq, REG "-" REG " ", st->start_address, addr - 1);
pt_dump_seq_printf(st->seq, " " REG " ", st->start_pa);
pt_dump_size(st->seq, addr - st->start_address);
}
static void note_prot_wx(struct pg_state *st, unsigned long addr)
{
pte_t pte = __pte(st->current_flags);
if (!st->check_wx)
return;
if (!pte_write(pte) || !pte_exec(pte))
return;
WARN_ONCE(IS_ENABLED(CONFIG_DEBUG_WX),
"powerpc/mm: Found insecure W+X mapping at address %p/%pS\n",
(void *)st->start_address, (void *)st->start_address);
st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
}
static void note_page_update_state(struct pg_state *st, unsigned long addr, int level, u64 val)
{
u64 flag = level >= 0 ? val & pg_level[level].mask : 0;
u64 pa = val & PTE_RPN_MASK;
st->level = level;
st->current_flags = flag;
st->start_address = addr;
st->start_pa = pa;
while (addr >= st->marker[1].start_address) {
st->marker++;
pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
}
}
static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val)
{
u64 flag = level >= 0 ? val & pg_level[level].mask : 0;
struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
/* At first no level is set */
if (st->level == -1) {
pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
note_page_update_state(st, addr, level, val);
/*
* Dump the section of virtual memory when:
* - the PTE flags from one entry to the next differs.
* - we change levels in the tree.
* - the address is in a different section of memory and is thus
* used for a different purpose, regardless of the flags.
*/
} else if (flag != st->current_flags || level != st->level ||
addr >= st->marker[1].start_address) {
/* Check the PTE flags */
if (st->current_flags) {
note_prot_wx(st, addr);
dump_addr(st, addr);
/* Dump all the flags */
if (pg_level[st->level].flag)
dump_flag_info(st, pg_level[st->level].flag,
st->current_flags,
pg_level[st->level].num);
pt_dump_seq_putc(st->seq, '\n');
}
/*
* Address indicates we have passed the end of the
* current section of virtual memory
*/
note_page_update_state(st, addr, level, val);
}
}
static void populate_markers(void)
{
int i = 0;
#ifdef CONFIG_PPC64
address_markers[i++].start_address = PAGE_OFFSET;
#else
address_markers[i++].start_address = TASK_SIZE;
#endif
#ifdef MODULES_VADDR
address_markers[i++].start_address = MODULES_VADDR;
address_markers[i++].start_address = MODULES_END;
#endif
address_markers[i++].start_address = VMALLOC_START;
address_markers[i++].start_address = VMALLOC_END;
#ifdef CONFIG_PPC64
address_markers[i++].start_address = ISA_IO_BASE;
address_markers[i++].start_address = ISA_IO_END;
address_markers[i++].start_address = PHB_IO_BASE;
address_markers[i++].start_address = PHB_IO_END;
address_markers[i++].start_address = IOREMAP_BASE;
address_markers[i++].start_address = IOREMAP_END;
/* What is the ifdef about? */
#ifdef CONFIG_PPC_BOOK3S_64
address_markers[i++].start_address = H_VMEMMAP_START;
#else
address_markers[i++].start_address = VMEMMAP_BASE;
#endif
#else /* !CONFIG_PPC64 */
address_markers[i++].start_address = ioremap_bot;
address_markers[i++].start_address = IOREMAP_TOP;
#ifdef CONFIG_HIGHMEM
address_markers[i++].start_address = PKMAP_BASE;
address_markers[i++].start_address = PKMAP_ADDR(LAST_PKMAP);
#endif
address_markers[i++].start_address = FIXADDR_START;
address_markers[i++].start_address = FIXADDR_TOP;
#endif /* CONFIG_PPC64 */
#ifdef CONFIG_KASAN
address_markers[i++].start_address = KASAN_SHADOW_START;
address_markers[i++].start_address = KASAN_SHADOW_END;
#endif
}
static int ptdump_show(struct seq_file *m, void *v)
{
struct pg_state st = {
.seq = m,
.marker = address_markers,
.level = -1,
.ptdump = {
.note_page = note_page,
.range = ptdump_range,
}
};
/* Traverse kernel page tables */
ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
return 0;
}
DEFINE_SHOW_ATTRIBUTE(ptdump);
static void __init build_pgtable_complete_mask(void)
{
unsigned int i, j;
for (i = 0; i < ARRAY_SIZE(pg_level); i++)
if (pg_level[i].flag)
for (j = 0; j < pg_level[i].num; j++)
pg_level[i].mask |= pg_level[i].flag[j].mask;
}
bool ptdump_check_wx(void)
{
struct pg_state st = {
.seq = NULL,
.marker = (struct addr_marker[]) {
{ 0, NULL},
{ -1, NULL},
},
.level = -1,
.check_wx = true,
.ptdump = {
.note_page = note_page,
.range = ptdump_range,
}
};
if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && !mmu_has_feature(MMU_FTR_KERNEL_RO))
return true;
ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
if (st.wx_pages) {
pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n",
st.wx_pages);
return false;
} else {
pr_info("Checked W+X mappings: passed, no W+X pages found\n");
return true;
}
}
static int __init ptdump_init(void)
{
#ifdef CONFIG_PPC64
if (!radix_enabled())
ptdump_range[0].start = KERN_VIRT_START;
else
ptdump_range[0].start = PAGE_OFFSET;
ptdump_range[0].end = PAGE_OFFSET + (PGDIR_SIZE * PTRS_PER_PGD);
#endif
populate_markers();
build_pgtable_complete_mask();
if (IS_ENABLED(CONFIG_PTDUMP_DEBUGFS))
debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
return 0;
}
device_initcall(ptdump_init);
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