Add an optional note_non_leaf parameter to ptdump, causing note_page to
be called on non-leaf descriptors. Implement this functionality on arm64
by printing table descriptors along with table-specific permission sets.
For arm64, break (1) the uniform number of columns for each descriptor,
and (2) the coalescing of large PTE regions, which are now split up by
PMD. This is a "good" thing since it makes the behavior and protection
bits set on page tables, such as PXNTable, more explicit.
Examples (spaces and last attribute condensed)
Before:
0xffff008440210000-0xffff008440400000 1984K PTE ro NX SHD AF NG UXN M...
0xffff008440400000-0xffff008441c00000 24M PMD ro NX SHD AF NG BLK UXN M...
0xffff008441c00000-0xffff008441dc0000 1792K PTE ro NX SHD AF NG UXN M...
0xffff008441dc0000-0xffff00844317b000 20204K PTE RW NX SHD AF NG UXN M...
After:
0xffff0fb640200000-0xffff0fb640400000 2M PMD TBL RW x NXTbl UXNTbl M...
0xffff0fb640200000-0xffff0fb640210000 64K PTE RW NX SHD AF NG UXN M...
0xffff0fb640210000-0xffff0fb640400000 1984K PTE ro NX SHD AF NG UXN M...
0xffff0fb640400000-0xffff0fb641c00000 24M PMD BLK ro SHD AF NG NX UXN ...
0xffff0fb641c00000-0xffff0fb641e00000 2M PMD TBL RW x NXTbl UXNTbl M...
0xffff0fb641c00000-0xffff0fb641dc0000 1792K PTE ro NX SHD AF NG UXN M...
0xffff0fb641dc0000-0xffff0fb641e00000 256K PTE RW NX SHD AF NG UXN ME...
Full dumps available at
github.com/maxwell-bland/linux-patch-data/tree/main/ptdump-non-leaf
Signed-off-by: Maxwell Bland <mbland@xxxxxxxxxxxx>
---
Dear Andrew,
> I was going to queue this while awaiting acks from arm people, but
> there's a large reject in Documentation/arch/arm64/ptdump.rst.
Ack, thank you and apologies, if I understand correctly, you are seeing
this issue on linux-next/akpm, I was not familiar with the submission
process. I was not able to reproduce on mm-unstable, linux-next/master,
mm/master, ... This reply (v2 commit) is cherry-picked to
linux-next/akpm.
A diff with linux-next/master for my original submission only returns:
611c611
< base-commit: a59668a9397e7245b26e9be85d23f242ff757ae8
> base-commit: 7d4768ae56014b3db93423e84f8794f173ec5c91
Regards,
Maxwell Bland
Documentation/arch/arm64/ptdump.rst | 125 ++++++++++++++++
arch/arm64/mm/ptdump.c | 224 +++++++++++++++++++++++++---
include/linux/ptdump.h | 1 +
mm/ptdump.c | 13 ++
4 files changed, 343 insertions(+), 20 deletions(-)
create mode 100644 Documentation/arch/arm64/ptdump.rst
diff --git a/Documentation/arch/arm64/ptdump.rst b/Documentation/arch/arm64/ptdump.rst
new file mode 100644
index 000000000000..0f38b92fd839
--- /dev/null
+++ b/Documentation/arch/arm64/ptdump.rst
@@ -0,0 +1,125 @@
+======================
+Kernel page table dump
+======================
+
+ptdump is a debugfs interface that provides a detailed dump of the kernel page
+tables. It offers a comprehensive overview of the kernel virtual memory layout
+as well as the attributes associated with the various regions in a
+human-readable format. It is useful to dump the kernel page tables to verify
+permissions and memory types. Examining the page table entries and permissions
+helps identify potential security vulnerabilities such as mappings with overly
+permissive access rights or improper memory protections.
+
+Memory hotplug allows dynamic expansion or contraction of available memory
+without requiring a system reboot. To maintain the consistency and integrity of
+the memory management data structures, arm64 makes use of the
+mem_hotplug_lock semaphore in write mode. Additionally, in read mode,
+mem_hotplug_lock supports an efficient implementation of
+get_online_mems() and put_online_mems(). These protect the offlining of
+memory being accessed by the ptdump code.
+
+In order to dump the kernel page tables, enable the following configurations
+and mount debugfs::
+
+ CONFIG_GENERIC_PTDUMP=y
+ CONFIG_PTDUMP_CORE=y
+ CONFIG_PTDUMP_DEBUGFS=y
+
+ mount -t debugfs nodev /sys/kernel/debug
+ cat /sys/kernel/debug/kernel_page_tables
+
+On analysing the output of cat /sys/kernel/debug/kernel_page_tables one can
+derive information about the virtual address range of a contiguous group of
+page table entries, followed by size of the memory region covered by this
+group, the hierarchical structure of the page tables and finally the attributes
+associated with each page in the group. Groups are broken up either according
+to a change in attributes or by parent descriptor, such as a PMD. Note that the
+set of attributes, and therefore formatting, is not equivalent between entry
+types. For example, PMD entries have a separate set of attributes from leaf
+level PTE entries, because they support both the UXNTable and PXNTable
+permission bits.
+
+The page attributes provide information about access permissions, execution
+capability, type of mapping such as leaf level PTE or block level PGD, PMD and
+PUD, and access status of a page within the kernel memory. Non-PTE block or
+page level entries are denoted with either "BLK" or "TBL", respectively.
+Assessing these attributes can assist in understanding the memory layout,
+access patterns and security characteristics of the kernel pages.
+
+Kernel virtual memory layout example::
+
+ start address end address size type leaf attributes
+ +-----------------------------------------------------------------------------------------------------------------+
+ | ---[ Linear Mapping start ]--- |
+ | ... |
+ | 0xffff0d02c3200000-0xffff0d02c3400000 2M PMD TBL RW x NXTbl UXNTbl MEM/NORMAL |
+ | 0xffff0d02c3200000-0xffff0d02c3218000 96K PTE ro NX SHD AF NG UXN MEM/NORMAL-TAGGED |
+ | 0xffff0d02c3218000-0xffff0d02c3250000 224K PTE RW NX SHD AF NG UXN MEM/NORMAL-TAGGED |
+ | 0xffff0d02c3250000-0xffff0d02c33b3000 1420K PTE ro NX SHD AF NG UXN MEM/NORMAL-TAGGED |
+ | 0xffff0d02c33b3000-0xffff0d02c3400000 308K PTE RW NX SHD AF NG UXN MEM/NORMAL-TAGGED |
+ | 0xffff0d02c3400000-0xffff0d02c3600000 2M PMD TBL RW x NXTbl UXNTbl MEM/NORMAL |
+ | 0xffff0d02c3400000-0xffff0d02c3600000 2M PTE RW NX SHD AF NG UXN MEM/NORMAL-TAGGED |
+ | ... |
+ | 0xffff0d02c3200000-0xffff0d02c3400000 2M PMD TBL RW x NXTbl UXNTbl MEM/NORMAL |
+ | ... |
+ | ---[ Linear Mapping end ]--- |
+ +-----------------------------------------------------------------------------------------------------------------+
+ | ---[ Modules start ]--- |
+ | ... |
+ | 0xffff800000000000-0xffff800000000080 128B PGD TBL RW x UXNTbl MEM/NORMAL |
+ | 0xffff800000000000-0xffff800080000000 2G PUD F BLK RW x MEM/NORMAL |
+ | ... |
+ | ---[ Modules end ]--- |
+ +-----------------------------------------------------------------------------------------------------------------+
+ | ---[ vmalloc() area ]--- |
+ | ... |
+ | 0xffff800080000000-0xffff8000c0000000 1G PUD TBL RW x UXNTbl MEM/NORMAL |
+ | ... |
+ | 0xffff800080200000-0xffff800080400000 2M PMD TBL RW x NXTbl UXNTbl MEM/NORMAL |
+ | 0xffff800080200000-0xffff80008022f000 188K PTE RW NX SHD AF NG UXN MEM/NORMAL |
+ | 0xffff80008022f000-0xffff800080230000 4K PTE F BLK RW x MEM/NORMAL |
+ | 0xffff800080230000-0xffff800080233000 12K PTE RW NX SHD AF NG UXN MEM/NORMAL |
+ | 0xffff800080233000-0xffff800080234000 4K PTE F BLK RW x MEM/NORMAL |
+ | 0xffff800080234000-0xffff800080237000 12K PTE RW NX SHD AF NG UXN MEM/NORMAL |
+ | ... |
+ | 0xffff800080400000-0xffff800084000000 60M PMD F BLK RW x x x MEM/NORMAL |
+ | ... |
+ | ---[ vmalloc() end ]--- |
+ +-----------------------------------------------------------------------------------------------------------------+
+ | ---[ vmemmap start ]--- |
+ | ... |
+ | 0xfffffe33cb000000-0xfffffe33cc000000 16M PMD BLK RW SHD AF NG NX UXN x x MEM/NORMAL |
+ | 0xfffffe33cc000000-0xfffffe3400000000 832M PMD F BLK RW x x x MEM/NORMAL |
+ | ... |
+ | ---[ vmemmap end ]--- |
+ +-----------------------------------------------------------------------------------------------------------------+
+ | ---[ PCI I/O start ]--- |
+ | ... |
+ | 0xffffffffc0800000-0xffffffffc0810000 64K PTE RW NX SHD AF NG UXN DEVICE/nGnRE |
+ | ... |
+ | ---[ PCI I/O end ]--- |
+ +-----------------------------------------------------------------------------------------------------------------+
+ | ---[ Fixmap start ]--- |
+ | ... |
+ | 0xffffffffff5f6000-0xffffffffff5f9000 12K PTE ro x SHD AF UXN MEM/NORMAL |
+ | 0xffffffffff5f9000-0xffffffffff5fa000 4K PTE ro NX SHD AF NG UXN MEM/NORMAL |
+ | ... |
+ | ---[ Fixmap end ]--- |
+ +-----------------------------------------------------------------------------------------------------------------+
+
+cat /sys/kernel/debug/kernel_page_tables output::
+
+ 0xffff000000000000-0xffff0d0000000000 13T PGD F BLK RW x MEM/NORMAL
+ 0xffff0d0000000000-0xffff0d0000000080 128B PGD TBL RW NXTbl UXNTbl MEM/NORMAL
+ 0xffff0d0000000000-0xffff0d02c0000000 11G PUD F BLK RW x MEM/NORMAL
+ 0xffff0d02c0000000-0xffff0d0300000000 1G PUD TBL RW NXTbl UXNTbl MEM/NORMAL
+ 0xffff0d02c0000000-0xffff0d02c0200000 2M PMD TBL RW x NXTbl UXNTbl MEM/NORMAL
+ 0xffff0d02c0000000-0xffff0d02c0200000 2M PTE RW NX SHD AF NG UXN MEM/NORMAL-TAGGED
+ 0xffff0d02c0200000-0xffff0d02c0400000 2M PMD TBL RW x NXTbl UXNTbl MEM/NORMAL
+ 0xffff0d02c0200000-0xffff0d02c0210000 64K PTE RW NX SHD AF NG UXN MEM/NORMAL-TAGGED
+ 0xffff0d02c0210000-0xffff0d02c0400000 1984K PTE ro NX SHD AF NG UXN MEM/NORMAL
+ 0xffff0d02c0400000-0xffff0d02c1c00000 24M PMD BLK ro SHD AF NG NX UXN x x MEM/NORMAL
+ 0xffff0d02c1c00000-0xffff0d02c1e00000 2M PMD TBL RW x NXTbl UXNTbl MEM/NORMAL
+ 0xffff0d02c1c00000-0xffff0d02c1dc0000 1792K PTE ro NX SHD AF NG UXN MEM/NORMAL
+ 0xffff0d02c1dc0000-0xffff0d02c1e00000 256K PTE RW NX SHD AF NG UXN MEM/NORMAL-TAGGED
+
diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 9bc4066c5bf3..6a8b2bcc9ac7 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -24,6 +24,7 @@
#include <asm/memory.h>
#include <asm/pgtable-hwdef.h>
#include <asm/ptdump.h>
+#include <asm/pgalloc.h>
enum address_markers_idx {
@@ -97,6 +98,11 @@ static const struct prot_bits pte_bits[] = {
.val = PTE_VALID,
.set = " ",
.clear = "F",
+ }, {
+ .mask = PTE_TABLE_BIT,
+ .val = PTE_TABLE_BIT,
+ .set = " ",
+ .clear = "BLK",
}, {
.mask = PTE_USER,
.val = PTE_USER,
@@ -132,11 +138,6 @@ static const struct prot_bits pte_bits[] = {
.val = PTE_CONT,
.set = "CON",
.clear = " ",
- }, {
- .mask = PTE_TABLE_BIT,
- .val = PTE_TABLE_BIT,
- .set = " ",
- .clear = "BLK",
}, {
.mask = PTE_UXN,
.val = PTE_UXN,
@@ -170,34 +171,206 @@ static const struct prot_bits pte_bits[] = {
}
};
+static const struct prot_bits pmd_bits[] = {
+ {
+ .mask = PMD_SECT_VALID,
+ .val = PMD_SECT_VALID,
+ .set = " ",
+ .clear = "F",
+ }, {
+ .mask = PMD_TABLE_BIT,
+ .val = PMD_TABLE_BIT,
+ .set = "TBL",
+ .clear = "BLK",
+ }, {
+ .mask = PMD_SECT_USER,
+ .val = PMD_SECT_USER,
+ .set = "USR",
+ .clear = " ",
+ }, {
+ .mask = PMD_SECT_RDONLY,
+ .val = PMD_SECT_RDONLY,
+ .set = "ro",
+ .clear = "RW",
+ }, {
+ .mask = PMD_SECT_S,
+ .val = PMD_SECT_S,
+ .set = "SHD",
+ .clear = " ",
+ }, {
+ .mask = PMD_SECT_AF,
+ .val = PMD_SECT_AF,
+ .set = "AF",
+ .clear = " ",
+ }, {
+ .mask = PMD_SECT_NG,
+ .val = PMD_SECT_NG,
+ .set = "NG",
+ .clear = " ",
+ }, {
+ .mask = PMD_SECT_CONT,
+ .val = PMD_SECT_CONT,
+ .set = "CON",
+ .clear = " ",
+ }, {
+ .mask = PMD_SECT_PXN,
+ .val = PMD_SECT_PXN,
+ .set = "NX",
+ .clear = "x ",
+ }, {
+ .mask = PMD_SECT_UXN,
+ .val = PMD_SECT_UXN,
+ .set = "UXN",
+ .clear = " ",
+ }, {
+ .mask = PMD_TABLE_PXN,
+ .val = PMD_TABLE_PXN,
+ .set = "NXTbl",
+ .clear = "x ",
+ }, {
+ .mask = PMD_TABLE_UXN,
+ .val = PMD_TABLE_UXN,
+ .set = "UXNTbl",
+ .clear = "x ",
+ }, {
+ .mask = PTE_GP,
+ .val = PTE_GP,
+ .set = "GP",
+ .clear = " ",
+ }, {
+ .mask = PMD_ATTRINDX_MASK,
+ .val = PMD_ATTRINDX(MT_DEVICE_nGnRnE),
+ .set = "DEVICE/nGnRnE",
+ }, {
+ .mask = PMD_ATTRINDX_MASK,
+ .val = PMD_ATTRINDX(MT_DEVICE_nGnRE),
+ .set = "DEVICE/nGnRE",
+ }, {
+ .mask = PMD_ATTRINDX_MASK,
+ .val = PMD_ATTRINDX(MT_NORMAL_NC),
+ .set = "MEM/NORMAL-NC",
+ }, {
+ .mask = PMD_ATTRINDX_MASK,
+ .val = PMD_ATTRINDX(MT_NORMAL),
+ .set = "MEM/NORMAL",
+ }, {
+ .mask = PMD_ATTRINDX_MASK,
+ .val = PMD_ATTRINDX(MT_NORMAL_TAGGED),
+ .set = "MEM/NORMAL-TAGGED",
+ }
+};
+
+static const struct prot_bits pud_bits[] = {
+ {
+ .mask = PUD_TYPE_SECT,
+ .val = PUD_TYPE_SECT,
+ .set = " ",
+ .clear = "F",
+ }, {
+ .mask = PUD_TABLE_BIT,
+ .val = PUD_TABLE_BIT,
+ .set = "TBL",
+ .clear = "BLK",
+ }, {
+ .mask = PTE_USER,
+ .val = PTE_USER,
+ .set = "USR",
+ .clear = " ",
+ }, {
+ .mask = PUD_SECT_RDONLY,
+ .val = PUD_SECT_RDONLY,
+ .set = "ro",
+ .clear = "RW",
+ }, {
+ .mask = PTE_SHARED,
+ .val = PTE_SHARED,
+ .set = "SHD",
+ .clear = " ",
+ }, {
+ .mask = PTE_AF,
+ .val = PTE_AF,
+ .set = "AF",
+ .clear = " ",
+ }, {
+ .mask = PTE_NG,
+ .val = PTE_NG,
+ .set = "NG",
+ .clear = " ",
+ }, {
+ .mask = PTE_CONT,
+ .val = PTE_CONT,
+ .set = "CON",
+ .clear = " ",
+ }, {
+ .mask = PUD_TABLE_PXN,
+ .val = PUD_TABLE_PXN,
+ .set = "NXTbl",
+ .clear = "x ",
+ }, {
+ .mask = PUD_TABLE_UXN,
+ .val = PUD_TABLE_UXN,
+ .set = "UXNTbl",
+ .clear = " ",
+ }, {
+ .mask = PTE_GP,
+ .val = PTE_GP,
+ .set = "GP",
+ .clear = " ",
+ }, {
+ .mask = PMD_ATTRINDX_MASK,
+ .val = PMD_ATTRINDX(MT_DEVICE_nGnRnE),
+ .set = "DEVICE/nGnRnE",
+ }, {
+ .mask = PMD_ATTRINDX_MASK,
+ .val = PMD_ATTRINDX(MT_DEVICE_nGnRE),
+ .set = "DEVICE/nGnRE",
+ }, {
+ .mask = PMD_ATTRINDX_MASK,
+ .val = PMD_ATTRINDX(MT_NORMAL_NC),
+ .set = "MEM/NORMAL-NC",
+ }, {
+ .mask = PMD_ATTRINDX_MASK,
+ .val = PMD_ATTRINDX(MT_NORMAL),
+ .set = "MEM/NORMAL",
+ }, {
+ .mask = PMD_ATTRINDX_MASK,
+ .val = PMD_ATTRINDX(MT_NORMAL_TAGGED),
+ .set = "MEM/NORMAL-TAGGED",
+ }
+};
+
struct pg_level {
const struct prot_bits *bits;
const char *name;
size_t num;
u64 mask;
+ unsigned long size;
};
static struct pg_level pg_level[] = {
{ /* pgd */
.name = "PGD",
- .bits = pte_bits,
- .num = ARRAY_SIZE(pte_bits),
+ .bits = pud_bits,
+ .num = ARRAY_SIZE(pud_bits),
+ .size = PGD_SIZE
}, { /* p4d */
.name = "P4D",
- .bits = pte_bits,
- .num = ARRAY_SIZE(pte_bits),
+ .bits = pud_bits,
+ .num = ARRAY_SIZE(pud_bits),
+ .size = P4D_SIZE
}, { /* pud */
.name = (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD",
- .bits = pte_bits,
- .num = ARRAY_SIZE(pte_bits),
+ .bits = pud_bits,
+ .num = ARRAY_SIZE(pud_bits),
}, { /* pmd */
.name = (CONFIG_PGTABLE_LEVELS > 2) ? "PMD" : "PGD",
- .bits = pte_bits,
- .num = ARRAY_SIZE(pte_bits),
+ .bits = pmd_bits,
+ .num = ARRAY_SIZE(pmd_bits),
}, { /* pte */
.name = "PTE",
.bits = pte_bits,
.num = ARRAY_SIZE(pte_bits),
+ .size = PAGE_SIZE
},
};
@@ -252,7 +425,7 @@ 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);
- static const char units[] = "KMGTPE";
+ static const char units[] = "BKMGTPE";
u64 prot = 0;
if (level >= 0)
@@ -263,8 +436,8 @@ static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
st->current_prot = prot;
st->start_address = addr;
pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
- } else if (prot != st->current_prot || level != st->level ||
- addr >= st->marker[1].start_address) {
+ } else if ((prot != st->current_prot || level != st->level ||
+ addr >= st->marker[1].start_address)) {
const char *unit = units;
unsigned long delta;
@@ -273,10 +446,20 @@ static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
note_prot_wx(st, addr);
}
- pt_dump_seq_printf(st->seq, "0x%016lx-0x%016lx ",
- st->start_address, addr);
+ /*
+ * Entries are coalesced into a single line, so non-leaf
+ * entries have no size relative to start_address
+ */
+ if (st->start_address != addr) {
+ pt_dump_seq_printf(st->seq, "0x%016lx-0x%016lx ",
+ st->start_address, addr);
+ delta = (addr - st->start_address);
+ } else {
+ pt_dump_seq_printf(st->seq, "0x%016lx-0x%016lx ", addr,
+ addr + pg_level[st->level].size);
+ delta = (pg_level[st->level].size);
+ }
- delta = (addr - st->start_address) >> 10;
while (!(delta & 1023) && unit[1]) {
delta >>= 10;
unit++;
@@ -322,7 +505,8 @@ void ptdump_walk(struct seq_file *s, struct ptdump_info *info)
.range = (struct ptdump_range[]){
{info->base_addr, end},
{0, 0}
- }
+ },
+ .note_non_leaf = true
}
};
diff --git a/include/linux/ptdump.h b/include/linux/ptdump.h
index 2a3a95586425..d32fa8515182 100644
--- a/include/linux/ptdump.h
+++ b/include/linux/ptdump.h
@@ -16,6 +16,7 @@ struct ptdump_state {
int level, u64 val);
void (*effective_prot)(struct ptdump_state *st, int level, u64 val);
const struct ptdump_range *range;
+ bool note_non_leaf;
};
void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd);
diff --git a/mm/ptdump.c b/mm/ptdump.c
index eea3d28d173c..aacbd499ffcd 100644
--- a/mm/ptdump.c
+++ b/mm/ptdump.c
@@ -40,6 +40,9 @@ static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
if (st->effective_prot)
st->effective_prot(st, 0, pgd_val(val));
+ if (st->note_non_leaf && !pgd_leaf(val))
+ st->note_page(st, addr, 0, pgd_val(val));
+
if (pgd_leaf(val)) {
st->note_page(st, addr, 0, pgd_val(val));
walk->action = ACTION_CONTINUE;
@@ -63,6 +66,9 @@ static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
if (st->effective_prot)
st->effective_prot(st, 1, p4d_val(val));
+ if (st->note_non_leaf && !p4d_leaf(val))
+ st->note_page(st, addr, 1, p4d_val(val));
+
if (p4d_leaf(val)) {
st->note_page(st, addr, 1, p4d_val(val));
walk->action = ACTION_CONTINUE;
@@ -86,6 +92,9 @@ static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
if (st->effective_prot)
st->effective_prot(st, 2, pud_val(val));
+ if (st->note_non_leaf && !pud_leaf(val))
+ st->note_page(st, addr, 2, pud_val(val));
+
if (pud_leaf(val)) {
st->note_page(st, addr, 2, pud_val(val));
walk->action = ACTION_CONTINUE;
@@ -107,6 +116,10 @@ static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
if (st->effective_prot)
st->effective_prot(st, 3, pmd_val(val));
+
+ if (st->note_non_leaf && !pmd_leaf(val))
+ st->note_page(st, addr, 3, pmd_val(val));
+
if (pmd_leaf(val)) {
st->note_page(st, addr, 3, pmd_val(val));
walk->action = ACTION_CONTINUE;
base-commit: 5f9df76887bf8170e8844f1907c13fbbb30e9c36
--
2.34.1
