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linuxdebug/arch/x86/mm/dump_pagetables.c

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// SPDX-License-Identifier: GPL-2.0-only
/*
* Debug helper to dump the current kernel pagetables of the system
* so that we can see what the various memory ranges are set to.
*
* (C) Copyright 2008 Intel Corporation
*
* Author: Arjan van de Ven <arjan@linux.intel.com>
*/
#include <linux/debugfs.h>
#include <linux/kasan.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/highmem.h>
#include <linux/pci.h>
#include <linux/ptdump.h>
#include <asm/e820/types.h>
/*
* The dumper groups pagetable entries of the same type into one, and for
* that it needs to keep some state when walking, and flush this state
* when a "break" in the continuity is found.
*/
struct pg_state {
struct ptdump_state ptdump;
int level;
pgprotval_t current_prot;
pgprotval_t effective_prot;
pgprotval_t prot_levels[5];
unsigned long start_address;
const struct addr_marker *marker;
unsigned long lines;
bool to_dmesg;
bool check_wx;
unsigned long wx_pages;
struct seq_file *seq;
};
struct addr_marker {
unsigned long start_address;
const char *name;
unsigned long max_lines;
};
/* Address space markers hints */
#ifdef CONFIG_X86_64
enum address_markers_idx {
USER_SPACE_NR = 0,
KERNEL_SPACE_NR,
#ifdef CONFIG_MODIFY_LDT_SYSCALL
LDT_NR,
#endif
LOW_KERNEL_NR,
VMALLOC_START_NR,
VMEMMAP_START_NR,
#ifdef CONFIG_KASAN
KASAN_SHADOW_START_NR,
KASAN_SHADOW_END_NR,
#endif
CPU_ENTRY_AREA_NR,
#ifdef CONFIG_X86_ESPFIX64
ESPFIX_START_NR,
#endif
#ifdef CONFIG_EFI
EFI_END_NR,
#endif
HIGH_KERNEL_NR,
MODULES_VADDR_NR,
MODULES_END_NR,
FIXADDR_START_NR,
END_OF_SPACE_NR,
};
static struct addr_marker address_markers[] = {
[USER_SPACE_NR] = { 0, "User Space" },
[KERNEL_SPACE_NR] = { (1UL << 63), "Kernel Space" },
[LOW_KERNEL_NR] = { 0UL, "Low Kernel Mapping" },
[VMALLOC_START_NR] = { 0UL, "vmalloc() Area" },
[VMEMMAP_START_NR] = { 0UL, "Vmemmap" },
#ifdef CONFIG_KASAN
/*
* These fields get initialized with the (dynamic)
* KASAN_SHADOW_{START,END} values in pt_dump_init().
*/
[KASAN_SHADOW_START_NR] = { 0UL, "KASAN shadow" },
[KASAN_SHADOW_END_NR] = { 0UL, "KASAN shadow end" },
#endif
#ifdef CONFIG_MODIFY_LDT_SYSCALL
[LDT_NR] = { 0UL, "LDT remap" },
#endif
[CPU_ENTRY_AREA_NR] = { CPU_ENTRY_AREA_BASE,"CPU entry Area" },
#ifdef CONFIG_X86_ESPFIX64
[ESPFIX_START_NR] = { ESPFIX_BASE_ADDR, "ESPfix Area", 16 },
#endif
#ifdef CONFIG_EFI
[EFI_END_NR] = { EFI_VA_END, "EFI Runtime Services" },
#endif
[HIGH_KERNEL_NR] = { __START_KERNEL_map, "High Kernel Mapping" },
[MODULES_VADDR_NR] = { MODULES_VADDR, "Modules" },
[MODULES_END_NR] = { MODULES_END, "End Modules" },
[FIXADDR_START_NR] = { FIXADDR_START, "Fixmap Area" },
[END_OF_SPACE_NR] = { -1, NULL }
};
#define INIT_PGD ((pgd_t *) &init_top_pgt)
#else /* CONFIG_X86_64 */
enum address_markers_idx {
USER_SPACE_NR = 0,
KERNEL_SPACE_NR,
VMALLOC_START_NR,
VMALLOC_END_NR,
#ifdef CONFIG_HIGHMEM
PKMAP_BASE_NR,
#endif
#ifdef CONFIG_MODIFY_LDT_SYSCALL
LDT_NR,
#endif
CPU_ENTRY_AREA_NR,
FIXADDR_START_NR,
END_OF_SPACE_NR,
};
static struct addr_marker address_markers[] = {
[USER_SPACE_NR] = { 0, "User Space" },
[KERNEL_SPACE_NR] = { PAGE_OFFSET, "Kernel Mapping" },
[VMALLOC_START_NR] = { 0UL, "vmalloc() Area" },
[VMALLOC_END_NR] = { 0UL, "vmalloc() End" },
#ifdef CONFIG_HIGHMEM
[PKMAP_BASE_NR] = { 0UL, "Persistent kmap() Area" },
#endif
#ifdef CONFIG_MODIFY_LDT_SYSCALL
[LDT_NR] = { 0UL, "LDT remap" },
#endif
[CPU_ENTRY_AREA_NR] = { 0UL, "CPU entry area" },
[FIXADDR_START_NR] = { 0UL, "Fixmap area" },
[END_OF_SPACE_NR] = { -1, NULL }
};
#define INIT_PGD (swapper_pg_dir)
#endif /* !CONFIG_X86_64 */
/* Multipliers for offsets within the PTEs */
#define PTE_LEVEL_MULT (PAGE_SIZE)
#define PMD_LEVEL_MULT (PTRS_PER_PTE * PTE_LEVEL_MULT)
#define PUD_LEVEL_MULT (PTRS_PER_PMD * PMD_LEVEL_MULT)
#define P4D_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
#define PGD_LEVEL_MULT (PTRS_PER_P4D * P4D_LEVEL_MULT)
#define pt_dump_seq_printf(m, to_dmesg, fmt, args...) \
({ \
if (to_dmesg) \
printk(KERN_INFO fmt, ##args); \
else \
if (m) \
seq_printf(m, fmt, ##args); \
})
#define pt_dump_cont_printf(m, to_dmesg, fmt, args...) \
({ \
if (to_dmesg) \
printk(KERN_CONT fmt, ##args); \
else \
if (m) \
seq_printf(m, fmt, ##args); \
})
/*
* Print a readable form of a pgprot_t to the seq_file
*/
static void printk_prot(struct seq_file *m, pgprotval_t pr, int level, bool dmsg)
{
static const char * const level_name[] =
{ "pgd", "p4d", "pud", "pmd", "pte" };
if (!(pr & _PAGE_PRESENT)) {
/* Not present */
pt_dump_cont_printf(m, dmsg, " ");
} else {
if (pr & _PAGE_USER)
pt_dump_cont_printf(m, dmsg, "USR ");
else
pt_dump_cont_printf(m, dmsg, " ");
if (pr & _PAGE_RW)
pt_dump_cont_printf(m, dmsg, "RW ");
else
pt_dump_cont_printf(m, dmsg, "ro ");
if (pr & _PAGE_PWT)
pt_dump_cont_printf(m, dmsg, "PWT ");
else
pt_dump_cont_printf(m, dmsg, " ");
if (pr & _PAGE_PCD)
pt_dump_cont_printf(m, dmsg, "PCD ");
else
pt_dump_cont_printf(m, dmsg, " ");
/* Bit 7 has a different meaning on level 3 vs 4 */
if (level <= 3 && pr & _PAGE_PSE)
pt_dump_cont_printf(m, dmsg, "PSE ");
else
pt_dump_cont_printf(m, dmsg, " ");
if ((level == 4 && pr & _PAGE_PAT) ||
((level == 3 || level == 2) && pr & _PAGE_PAT_LARGE))
pt_dump_cont_printf(m, dmsg, "PAT ");
else
pt_dump_cont_printf(m, dmsg, " ");
if (pr & _PAGE_GLOBAL)
pt_dump_cont_printf(m, dmsg, "GLB ");
else
pt_dump_cont_printf(m, dmsg, " ");
if (pr & _PAGE_NX)
pt_dump_cont_printf(m, dmsg, "NX ");
else
pt_dump_cont_printf(m, dmsg, "x ");
}
pt_dump_cont_printf(m, dmsg, "%s\n", level_name[level]);
}
static void note_wx(struct pg_state *st, unsigned long addr)
{
unsigned long npages;
npages = (addr - st->start_address) / PAGE_SIZE;
#ifdef CONFIG_PCI_BIOS
/*
* If PCI BIOS is enabled, the PCI BIOS area is forced to WX.
* Inform about it, but avoid the warning.
*/
if (pcibios_enabled && st->start_address >= PAGE_OFFSET + BIOS_BEGIN &&
addr <= PAGE_OFFSET + BIOS_END) {
pr_warn_once("x86/mm: PCI BIOS W+X mapping %lu pages\n", npages);
return;
}
#endif
/* Account the WX pages */
st->wx_pages += npages;
WARN_ONCE(__supported_pte_mask & _PAGE_NX,
"x86/mm: Found insecure W+X mapping at address %pS\n",
(void *)st->start_address);
}
static void effective_prot(struct ptdump_state *pt_st, int level, u64 val)
{
struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
pgprotval_t prot = val & PTE_FLAGS_MASK;
pgprotval_t effective;
if (level > 0) {
pgprotval_t higher_prot = st->prot_levels[level - 1];
effective = (higher_prot & prot & (_PAGE_USER | _PAGE_RW)) |
((higher_prot | prot) & _PAGE_NX);
} else {
effective = prot;
}
st->prot_levels[level] = effective;
}
/*
* This function gets called on a break in a continuous series
* of PTE entries; the next one is different so we need to
* print what we collected so far.
*/
static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
u64 val)
{
struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
pgprotval_t new_prot, new_eff;
pgprotval_t cur, eff;
static const char units[] = "BKMGTPE";
struct seq_file *m = st->seq;
new_prot = val & PTE_FLAGS_MASK;
if (!val)
new_eff = 0;
else
new_eff = st->prot_levels[level];
/*
* If we have a "break" in the series, we need to flush the state that
* we have now. "break" is either changing perms, levels or
* address space marker.
*/
cur = st->current_prot;
eff = st->effective_prot;
if (st->level == -1) {
/* First entry */
st->current_prot = new_prot;
st->effective_prot = new_eff;
st->level = level;
st->marker = address_markers;
st->lines = 0;
pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
st->marker->name);
} else if (new_prot != cur || new_eff != eff || level != st->level ||
addr >= st->marker[1].start_address) {
const char *unit = units;
unsigned long delta;
int width = sizeof(unsigned long) * 2;
if (st->check_wx && (eff & _PAGE_RW) && !(eff & _PAGE_NX))
note_wx(st, addr);
/*
* Now print the actual finished series
*/
if (!st->marker->max_lines ||
st->lines < st->marker->max_lines) {
pt_dump_seq_printf(m, st->to_dmesg,
"0x%0*lx-0x%0*lx ",
width, st->start_address,
width, addr);
delta = addr - st->start_address;
while (!(delta & 1023) && unit[1]) {
delta >>= 10;
unit++;
}
pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ",
delta, *unit);
printk_prot(m, st->current_prot, st->level,
st->to_dmesg);
}
st->lines++;
/*
* We print markers for special areas of address space,
* such as the start of vmalloc space etc.
* This helps in the interpretation.
*/
if (addr >= st->marker[1].start_address) {
if (st->marker->max_lines &&
st->lines > st->marker->max_lines) {
unsigned long nskip =
st->lines - st->marker->max_lines;
pt_dump_seq_printf(m, st->to_dmesg,
"... %lu entr%s skipped ... \n",
nskip,
nskip == 1 ? "y" : "ies");
}
st->marker++;
st->lines = 0;
pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
st->marker->name);
}
st->start_address = addr;
st->current_prot = new_prot;
st->effective_prot = new_eff;
st->level = level;
}
}
static void ptdump_walk_pgd_level_core(struct seq_file *m,
struct mm_struct *mm, pgd_t *pgd,
bool checkwx, bool dmesg)
{
const struct ptdump_range ptdump_ranges[] = {
#ifdef CONFIG_X86_64
{0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
{GUARD_HOLE_END_ADDR, ~0UL},
#else
{0, ~0UL},
#endif
{0, 0}
};
struct pg_state st = {
.ptdump = {
.note_page = note_page,
.effective_prot = effective_prot,
.range = ptdump_ranges
},
.level = -1,
.to_dmesg = dmesg,
.check_wx = checkwx,
.seq = m
};
ptdump_walk_pgd(&st.ptdump, mm, pgd);
if (!checkwx)
return;
if (st.wx_pages)
pr_info("x86/mm: Checked W+X mappings: FAILED, %lu W+X pages found.\n",
st.wx_pages);
else
pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
}
void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm)
{
ptdump_walk_pgd_level_core(m, mm, mm->pgd, false, true);
}
void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm,
bool user)
{
pgd_t *pgd = mm->pgd;
#ifdef CONFIG_PAGE_TABLE_ISOLATION
if (user && boot_cpu_has(X86_FEATURE_PTI))
pgd = kernel_to_user_pgdp(pgd);
#endif
ptdump_walk_pgd_level_core(m, mm, pgd, false, false);
}
EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level_debugfs);
void ptdump_walk_user_pgd_level_checkwx(void)
{
#ifdef CONFIG_PAGE_TABLE_ISOLATION
pgd_t *pgd = INIT_PGD;
if (!(__supported_pte_mask & _PAGE_NX) ||
!boot_cpu_has(X86_FEATURE_PTI))
return;
pr_info("x86/mm: Checking user space page tables\n");
pgd = kernel_to_user_pgdp(pgd);
ptdump_walk_pgd_level_core(NULL, &init_mm, pgd, true, false);
#endif
}
void ptdump_walk_pgd_level_checkwx(void)
{
ptdump_walk_pgd_level_core(NULL, &init_mm, INIT_PGD, true, false);
}
static int __init pt_dump_init(void)
{
/*
* Various markers are not compile-time constants, so assign them
* here.
*/
#ifdef CONFIG_X86_64
address_markers[LOW_KERNEL_NR].start_address = PAGE_OFFSET;
address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
address_markers[VMEMMAP_START_NR].start_address = VMEMMAP_START;
#ifdef CONFIG_MODIFY_LDT_SYSCALL
address_markers[LDT_NR].start_address = LDT_BASE_ADDR;
#endif
#ifdef CONFIG_KASAN
address_markers[KASAN_SHADOW_START_NR].start_address = KASAN_SHADOW_START;
address_markers[KASAN_SHADOW_END_NR].start_address = KASAN_SHADOW_END;
#endif
#endif
#ifdef CONFIG_X86_32
address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
# ifdef CONFIG_HIGHMEM
address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
# endif
address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
address_markers[CPU_ENTRY_AREA_NR].start_address = CPU_ENTRY_AREA_BASE;
# ifdef CONFIG_MODIFY_LDT_SYSCALL
address_markers[LDT_NR].start_address = LDT_BASE_ADDR;
# endif
#endif
return 0;
}
__initcall(pt_dump_init);
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