* [PATCH] LoongArch: Add support to dump the kernel page tables
@ 2026-06-29 7:43 haoran.jiang
2026-06-29 14:00 ` Huacai Chen
0 siblings, 1 reply; 3+ messages in thread
From: haoran.jiang @ 2026-06-29 7:43 UTC (permalink / raw)
To: chenhuacai
Cc: loongarch, linux-kernel, kernel, yangtiezhu, Haoran Jiang,
Xiujie Jiang
From: Haoran Jiang <jianghaoran@kylinos.cn>
In a similar manner to riscv,arm64,x86 etc.,this patch allows
dumping the page tables of the LoongArch page-mapped virtual memory
region via a debugfs file, which is useful for kernel developers to
inspect page table layouts and verify permissions and type settings.
Co-developed-by: Xiujie Jiang <jiangxiujie@kylinos.cn>
Signed-off-by: Xiujie Jiang <jiangxiujie@kylinos.cn>
Signed-off-by: Haoran Jiang <jianghaoran@kylinos.cn>
---
arch/loongarch/Kconfig | 1 +
arch/loongarch/include/asm/ptdump.h | 61 ++++
arch/loongarch/mm/Makefile | 2 +
arch/loongarch/mm/ptdump.c | 417 ++++++++++++++++++++++++++++
arch/loongarch/mm/ptdump_debugfs.c | 22 ++
5 files changed, 503 insertions(+)
create mode 100644 arch/loongarch/include/asm/ptdump.h
create mode 100644 arch/loongarch/mm/ptdump.c
create mode 100644 arch/loongarch/mm/ptdump_debugfs.c
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index bec7cc1d72ee..e97fe97e1955 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -25,6 +25,7 @@ config LOONGARCH
select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
select ARCH_HAS_PREEMPT_LAZY
select ARCH_HAS_PTE_SPECIAL if 64BIT
+ select ARCH_HAS_PTDUMP
select ARCH_HAS_SET_MEMORY
select ARCH_HAS_SET_DIRECT_MAP
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
diff --git a/arch/loongarch/include/asm/ptdump.h b/arch/loongarch/include/asm/ptdump.h
new file mode 100644
index 000000000000..4590ea56abe6
--- /dev/null
+++ b/arch/loongarch/include/asm/ptdump.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __ASM_PTDUMP_H
+#define __ASM_PTDUMP_H
+
+#include <linux/ptdump.h>
+#include <linux/mm_types.h>
+#include <linux/seq_file.h>
+
+/*
+ * 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.
+ */
+struct pg_state {
+ struct ptdump_state ptdump;
+ struct seq_file *seq;
+ const struct addr_marker *marker;
+ unsigned long start_address;
+ unsigned long start_pa;
+ unsigned long last_pa;
+ int level;
+ u64 current_prot;
+ bool check_wx;
+ unsigned long wx_pages;
+};
+
+/* Address marker */
+struct addr_marker {
+ unsigned long start_address;
+ const char *name;
+};
+
+/* Private information for debugfs */
+struct ptd_mm_info {
+ struct mm_struct *mm;
+ const struct addr_marker *markers;
+ unsigned long base_addr;
+ unsigned long end;
+};
+
+/* Page Table Entry */
+struct prot_bits {
+ u64 mask;
+ u64 val;
+ const char *set;
+ const char *clear;
+};
+
+/* Page Level */
+struct pg_level {
+ const char *name;
+ u64 mask;
+};
+
+void ptdump_walk(struct seq_file *s, struct ptd_mm_info *pinfo);
+void __init ptdump_debugfs_register(struct ptd_mm_info *info, const char *name);
+
+#endif /* __ASM_PTDUMP_H */
+
diff --git a/arch/loongarch/mm/Makefile b/arch/loongarch/mm/Makefile
index 2aae3773de77..da9e6fee0439 100644
--- a/arch/loongarch/mm/Makefile
+++ b/arch/loongarch/mm/Makefile
@@ -10,5 +10,7 @@ obj-y += init.o cache.o tlb.o tlbex.o extable.o \
obj-$(CONFIG_HIGHMEM) += highmem.o
obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
obj-$(CONFIG_KASAN) += kasan_init.o
+obj-$(CONFIG_PTDUMP) += ptdump.o
+obj-$(CONFIG_PTDUMP_DEBUGFS) += ptdump_debugfs.o
KASAN_SANITIZE_kasan_init.o := n
diff --git a/arch/loongarch/mm/ptdump.c b/arch/loongarch/mm/ptdump.c
new file mode 100644
index 000000000000..cab6dad18150
--- /dev/null
+++ b/arch/loongarch/mm/ptdump.c
@@ -0,0 +1,417 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Derived from riscv implementation
+ */
+
+#include <linux/init.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/ptdump.h>
+#include <linux/pgtable.h>
+#include <asm/kasan.h>
+#include <asm/ptdump.h>
+
+#define _PAGE_PLV_VAL 0x0
+
+#define pt_dump_seq_printf(m, fmt, args...) \
+({ \
+ if (m) \
+ seq_printf(m, fmt, ##args); \
+})
+
+#define pt_dump_seq_puts(m, fmt) \
+({ \
+ if (m) \
+ seq_puts(m, fmt); \
+})
+
+enum address_markers_idx {
+ PCI_IO_START_NR,
+ PCI_IO_END_NR,
+ MODULES_START_NR,
+ MODULES_END_NR,
+ VMALLOC_START_NR,
+ VMALLOC_END_NR,
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+ VMEMMAP_START_NR,
+ VMEMMAP_END_NR,
+#endif
+#ifdef CONFIG_KFENCE
+ KFENCE_AREA_START_NR,
+ KFENCE_AREA_END_NR,
+#endif
+#ifdef CONFIG_KASAN
+ KASAN_SHADOW_START_NR,
+ KASAN_SHADOW_END_NR,
+#endif
+ FIXMAP_START_NR,
+ FIXMAP_END_NR,
+ END_OF_SPACE_NR
+};
+
+
+
+static struct addr_marker address_markers[] = {
+ {0, "PCI I/O start"},
+ {0, "PCI I/O end"},
+ {0, "modules start"},
+ {0, "modules end"},
+ {0, "vmalloc() area"},
+ {0, "vmalloc() end"},
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+ {0, "vmemmap start"},
+ {0, "vmemmap end"},
+#endif
+#ifdef CONFIG_KFENCE
+ {0, "kfence area start"},
+ {0, "kfence area end"},
+#endif
+#ifdef CONFIG_KASAN
+ {0, "Kasan shadow start"},
+ {0, "Kasan shadow end"},
+#endif
+ {0, "Fixmap start"},
+ {0, "Fixmap end"},
+ {-1, NULL},
+};
+
+
+static struct ptd_mm_info kernel_ptd_info = {
+ .mm = &init_mm,
+ .markers = address_markers,
+ .base_addr = 0,
+ .end = ULONG_MAX,
+};
+
+static const struct prot_bits pte_bits[] = {
+ {
+ .mask = _PAGE_VALID,
+ .val = _PAGE_VALID,
+ .set = "V",
+ .clear = " ",
+ }, {
+ .mask = _PAGE_DIRTY,
+ .val = _PAGE_DIRTY,
+ .set = "D",
+ .clear = " ",
+ }, {
+ .mask = _PAGE_PLV,
+ .val = _PAGE_PLV_VAL,
+ .set = "KERN",
+ .clear = "USR ",
+ }, {
+ .mask = _CACHE_MASK,
+ .val = _CACHE_MASK,
+ .set = " ",
+ .clear = "SUC",
+ }, {
+ .mask = _PAGE_GLOBAL,
+ .val = _PAGE_GLOBAL,
+ .set = "G",
+ .clear = " ",
+ }, {
+ .mask = _PAGE_PRESENT,
+ .val = _PAGE_PRESENT,
+ .set = "P",
+ .clear = " ",
+ }, {
+ .mask = _PAGE_WRITE,
+ .val = _PAGE_WRITE,
+ .set = "W",
+ .clear = " ",
+ }, {
+ .mask = _PAGE_HGLOBAL,
+ .val = _PAGE_HGLOBAL,
+ .set = "HG",
+ .clear = " ",
+ }, {
+ .mask = _PAGE_NO_READ,
+ .val = _PAGE_NO_READ,
+ .set = "NR",
+ .clear = " ",
+ }, {
+ .mask = _PAGE_NO_EXEC,
+ .val = _PAGE_NO_EXEC,
+ .set = "NX",
+ .clear = " ",
+ }, {
+ .mask = _PAGE_RPLV,
+ .val = _PAGE_RPLV,
+ .set = "RPLV",
+ .clear = " ",
+ }
+};
+
+static struct pg_level pg_level[] = {
+ { /* pgd */
+ .name = "PGD",
+ }, { /* p4d */
+ .name = (CONFIG_PGTABLE_LEVELS > 4) ? "P4D" : "PGD",
+ }, { /* pud */
+ .name = (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD",
+ }, { /* pmd */
+ .name = (CONFIG_PGTABLE_LEVELS > 2) ? "PMD" : "PGD",
+ }, { /* pte */
+ .name = "PTE",
+ },
+};
+
+static void dump_prot(struct pg_state *st)
+{
+
+ unsigned int i;
+
+ for (i = 0; i < ARRAY_SIZE(pte_bits); i++) {
+ const char *s;
+
+ if (pte_bits[i].mask == _CACHE_MASK) {
+ if ((st->current_prot & pte_bits[i].mask) == _CACHE_CC)
+ s = "CC ";
+ else if ((st->current_prot & pte_bits[i].mask) == _CACHE_WUC)
+ s = "WUC";
+ else
+ s = pte_bits[i].clear;
+ } else if (pte_bits[i].mask == _PAGE_GLOBAL) {
+ if ((st->current_prot & pte_bits[i].mask) == pte_bits[i].val) {
+ if (st->level != 4)
+ s = "PSE";
+ else
+ s = pte_bits[i].set;
+ } else {
+ s = pte_bits[i].clear;
+ }
+
+ } else {
+ if ((st->current_prot & pte_bits[i].mask) == pte_bits[i].val)
+ s = pte_bits[i].set;
+ else
+ s = pte_bits[i].clear;
+ }
+
+
+ if (s)
+ pt_dump_seq_printf(st->seq, " %s", s);
+ }
+
+}
+
+
+#ifdef CONFIG_64BIT
+#define ADDR_FORMAT "0x%016lx"
+#else
+#define ADDR_FORMAT "0x%08lx"
+#endif
+static void dump_addr(struct pg_state *st, unsigned long addr)
+{
+ static const char units[] = "KMGTPE";
+ const char *unit = units;
+ unsigned long delta;
+
+ pt_dump_seq_printf(st->seq, ADDR_FORMAT "-" ADDR_FORMAT " ",
+ st->start_address, addr);
+
+ pt_dump_seq_printf(st->seq, " " ADDR_FORMAT " ", st->start_pa);
+ delta = (addr - st->start_address) >> 10;
+
+ while (!(delta & 1023) && unit[1]) {
+ delta >>= 10;
+ unit++;
+ }
+
+ pt_dump_seq_printf(st->seq, "%9lu%c %s", delta, *unit,
+ pg_level[st->level].name);
+}
+
+static void note_prot_wx(struct pg_state *st, unsigned long addr)
+{
+ if (!st->check_wx)
+ return;
+ if ((st->current_prot & _PAGE_WRITE) == 0)
+ return;
+ if ((st->current_prot & _PAGE_NO_EXEC) == _PAGE_NO_EXEC)
+ return;
+
+ st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
+
+}
+
+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);
+ u64 pa = PFN_PHYS(pte_pfn(__pte(val)));
+ u64 prot = 0;
+
+ if (level >= 0)
+ prot = val & pg_level[level].mask;
+
+ if (st->level == -1) {
+ st->level = level;
+ st->current_prot = prot;
+ st->start_address = addr;
+ st->start_pa = pa;
+ st->last_pa = pa;
+ 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) {
+ if (st->current_prot) {
+ note_prot_wx(st, addr);
+ dump_addr(st, addr);
+ dump_prot(st);
+ pt_dump_seq_puts(st->seq, "\n");
+ }
+
+ while (addr >= st->marker[1].start_address) {
+ st->marker++;
+ pt_dump_seq_printf(st->seq, "---[ %s ]---\n",
+ st->marker->name);
+ }
+
+ st->start_address = addr;
+ st->start_pa = pa;
+ st->last_pa = pa;
+ st->current_prot = prot;
+ st->level = level;
+ } else {
+ st->last_pa = pa;
+ }
+}
+
+static void note_page_pte(struct ptdump_state *pt_st, unsigned long addr, pte_t pte)
+{
+ note_page(pt_st, addr, 4, pte_val(pte));
+}
+
+static void note_page_pmd(struct ptdump_state *pt_st, unsigned long addr, pmd_t pmd)
+{
+ note_page(pt_st, addr, 3, pmd_val(pmd));
+}
+
+static void note_page_pud(struct ptdump_state *pt_st, unsigned long addr, pud_t pud)
+{
+ note_page(pt_st, addr, 2, pud_val(pud));
+}
+
+static void note_page_p4d(struct ptdump_state *pt_st, unsigned long addr, p4d_t p4d)
+{
+ note_page(pt_st, addr, 1, p4d_val(p4d));
+}
+
+static void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd)
+{
+ note_page(pt_st, addr, 0, pgd_val(pgd));
+}
+
+static void note_page_flush(struct ptdump_state *pt_st)
+{
+ pte_t pte_zero = {0};
+
+ note_page(pt_st, 0, -1, pte_val(pte_zero));
+}
+
+void ptdump_walk(struct seq_file *s, struct ptd_mm_info *pinfo)
+{
+ struct pg_state st = {
+ .seq = s,
+ .marker = pinfo->markers,
+ .level = -1,
+ .ptdump = {
+ .note_page_pte = note_page_pte,
+ .note_page_pmd = note_page_pmd,
+ .note_page_pud = note_page_pud,
+ .note_page_p4d = note_page_p4d,
+ .note_page_pgd = note_page_pgd,
+ .note_page_flush = note_page_flush,
+ .range = (struct ptdump_range[]) {
+ {pinfo->base_addr, pinfo->end},
+ {0, 0}
+ }
+ }
+ };
+
+ ptdump_walk_pgd(&st.ptdump, pinfo->mm, NULL);
+}
+
+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_pte = note_page_pte,
+ .note_page_pmd = note_page_pmd,
+ .note_page_pud = note_page_pud,
+ .note_page_p4d = note_page_p4d,
+ .note_page_pgd = note_page_pgd,
+ .note_page_flush = note_page_flush,
+ .range = (struct ptdump_range[]) {
+ {vm_map_base, ULONG_MAX},
+ {0, 0}
+ }
+ }
+ };
+
+ 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;
+ }
+
+ pr_info("Checked W+X mappings: passed, no W+X pages found\n");
+
+ return true;
+}
+
+
+static int __init ptdump_init(void)
+{
+ unsigned int i, j;
+
+ address_markers[PCI_IO_START_NR].start_address = (unsigned long)PCI_IOBASE;
+ address_markers[PCI_IO_END_NR].start_address = (unsigned long)PCI_IOBASE + IO_SPACE_LIMIT;
+
+ address_markers[MODULES_START_NR].start_address = MODULES_VADDR;
+ address_markers[MODULES_END_NR].start_address = MODULES_END;
+
+ address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
+ address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
+
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+ address_markers[VMEMMAP_START_NR].start_address = (unsigned long)vmemmap;
+ address_markers[VMEMMAP_END_NR].start_address = VMEMMAP_END;
+#endif
+
+#ifdef CONFIG_KFENCE
+ address_markers[KFENCE_AREA_START_NR].start_address = KFENCE_AREA_START;
+ address_markers[KFENCE_AREA_END_NR].start_address = KFENCE_AREA_END;
+#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
+
+ address_markers[FIXMAP_START_NR].start_address = FIXADDR_START;
+ address_markers[FIXMAP_END_NR].start_address = FIXADDR_TOP;
+
+ kernel_ptd_info.base_addr = vm_map_base;
+
+ for (i = 0; i < ARRAY_SIZE(pg_level); i++) {
+ for (j = 0; j < ARRAY_SIZE(pte_bits); j++)
+ pg_level[i].mask |= pte_bits[j].mask;
+ }
+
+ ptdump_debugfs_register(&kernel_ptd_info, "kernel_page_tables");
+
+ return 0;
+}
+
+device_initcall(ptdump_init);
diff --git a/arch/loongarch/mm/ptdump_debugfs.c b/arch/loongarch/mm/ptdump_debugfs.c
new file mode 100644
index 000000000000..aa6169f6aa3a
--- /dev/null
+++ b/arch/loongarch/mm/ptdump_debugfs.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+
+#include <asm/ptdump.h>
+#include <asm/pgtable.h>
+#include <asm/kasan.h>
+
+static int ptdump_show(struct seq_file *m, void *v)
+{
+ struct ptd_mm_info *info = m->private;
+
+ ptdump_walk(m, info);
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(ptdump);
+
+void __init ptdump_debugfs_register(struct ptd_mm_info *info, const char *name)
+{
+ debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
+}
+
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] LoongArch: Add support to dump the kernel page tables
2026-06-29 7:43 [PATCH] LoongArch: Add support to dump the kernel page tables haoran.jiang
@ 2026-06-29 14:00 ` Huacai Chen
2026-06-30 12:09 ` haoran.jiang
0 siblings, 1 reply; 3+ messages in thread
From: Huacai Chen @ 2026-06-29 14:00 UTC (permalink / raw)
To: haoran.jiang
Cc: loongarch, linux-kernel, kernel, yangtiezhu, Haoran Jiang,
Xiujie Jiang
Hi, Haoran,
On Mon, Jun 29, 2026 at 3:44 PM <haoran.jiang@linux.dev> wrote:
>
> From: Haoran Jiang <jianghaoran@kylinos.cn>
>
> In a similar manner to riscv,arm64,x86 etc.,this patch allows
> dumping the page tables of the LoongArch page-mapped virtual memory
> region via a debugfs file, which is useful for kernel developers to
> inspect page table layouts and verify permissions and type settings.
I like the RISC-V version that put everything in ptdump.c.
Huacai
>
> Co-developed-by: Xiujie Jiang <jiangxiujie@kylinos.cn>
> Signed-off-by: Xiujie Jiang <jiangxiujie@kylinos.cn>
> Signed-off-by: Haoran Jiang <jianghaoran@kylinos.cn>
> ---
> arch/loongarch/Kconfig | 1 +
> arch/loongarch/include/asm/ptdump.h | 61 ++++
> arch/loongarch/mm/Makefile | 2 +
> arch/loongarch/mm/ptdump.c | 417 ++++++++++++++++++++++++++++
> arch/loongarch/mm/ptdump_debugfs.c | 22 ++
> 5 files changed, 503 insertions(+)
> create mode 100644 arch/loongarch/include/asm/ptdump.h
> create mode 100644 arch/loongarch/mm/ptdump.c
> create mode 100644 arch/loongarch/mm/ptdump_debugfs.c
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index bec7cc1d72ee..e97fe97e1955 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -25,6 +25,7 @@ config LOONGARCH
> select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> select ARCH_HAS_PREEMPT_LAZY
> select ARCH_HAS_PTE_SPECIAL if 64BIT
> + select ARCH_HAS_PTDUMP
> select ARCH_HAS_SET_MEMORY
> select ARCH_HAS_SET_DIRECT_MAP
> select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
> diff --git a/arch/loongarch/include/asm/ptdump.h b/arch/loongarch/include/asm/ptdump.h
> new file mode 100644
> index 000000000000..4590ea56abe6
> --- /dev/null
> +++ b/arch/loongarch/include/asm/ptdump.h
> @@ -0,0 +1,61 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef __ASM_PTDUMP_H
> +#define __ASM_PTDUMP_H
> +
> +#include <linux/ptdump.h>
> +#include <linux/mm_types.h>
> +#include <linux/seq_file.h>
> +
> +/*
> + * 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.
> + */
> +struct pg_state {
> + struct ptdump_state ptdump;
> + struct seq_file *seq;
> + const struct addr_marker *marker;
> + unsigned long start_address;
> + unsigned long start_pa;
> + unsigned long last_pa;
> + int level;
> + u64 current_prot;
> + bool check_wx;
> + unsigned long wx_pages;
> +};
> +
> +/* Address marker */
> +struct addr_marker {
> + unsigned long start_address;
> + const char *name;
> +};
> +
> +/* Private information for debugfs */
> +struct ptd_mm_info {
> + struct mm_struct *mm;
> + const struct addr_marker *markers;
> + unsigned long base_addr;
> + unsigned long end;
> +};
> +
> +/* Page Table Entry */
> +struct prot_bits {
> + u64 mask;
> + u64 val;
> + const char *set;
> + const char *clear;
> +};
> +
> +/* Page Level */
> +struct pg_level {
> + const char *name;
> + u64 mask;
> +};
> +
> +void ptdump_walk(struct seq_file *s, struct ptd_mm_info *pinfo);
> +void __init ptdump_debugfs_register(struct ptd_mm_info *info, const char *name);
> +
> +#endif /* __ASM_PTDUMP_H */
> +
> diff --git a/arch/loongarch/mm/Makefile b/arch/loongarch/mm/Makefile
> index 2aae3773de77..da9e6fee0439 100644
> --- a/arch/loongarch/mm/Makefile
> +++ b/arch/loongarch/mm/Makefile
> @@ -10,5 +10,7 @@ obj-y += init.o cache.o tlb.o tlbex.o extable.o \
> obj-$(CONFIG_HIGHMEM) += highmem.o
> obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
> obj-$(CONFIG_KASAN) += kasan_init.o
> +obj-$(CONFIG_PTDUMP) += ptdump.o
> +obj-$(CONFIG_PTDUMP_DEBUGFS) += ptdump_debugfs.o
>
> KASAN_SANITIZE_kasan_init.o := n
> diff --git a/arch/loongarch/mm/ptdump.c b/arch/loongarch/mm/ptdump.c
> new file mode 100644
> index 000000000000..cab6dad18150
> --- /dev/null
> +++ b/arch/loongarch/mm/ptdump.c
> @@ -0,0 +1,417 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Derived from riscv implementation
> + */
> +
> +#include <linux/init.h>
> +#include <linux/debugfs.h>
> +#include <linux/seq_file.h>
> +#include <linux/ptdump.h>
> +#include <linux/pgtable.h>
> +#include <asm/kasan.h>
> +#include <asm/ptdump.h>
> +
> +#define _PAGE_PLV_VAL 0x0
> +
> +#define pt_dump_seq_printf(m, fmt, args...) \
> +({ \
> + if (m) \
> + seq_printf(m, fmt, ##args); \
> +})
> +
> +#define pt_dump_seq_puts(m, fmt) \
> +({ \
> + if (m) \
> + seq_puts(m, fmt); \
> +})
> +
> +enum address_markers_idx {
> + PCI_IO_START_NR,
> + PCI_IO_END_NR,
> + MODULES_START_NR,
> + MODULES_END_NR,
> + VMALLOC_START_NR,
> + VMALLOC_END_NR,
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> + VMEMMAP_START_NR,
> + VMEMMAP_END_NR,
> +#endif
> +#ifdef CONFIG_KFENCE
> + KFENCE_AREA_START_NR,
> + KFENCE_AREA_END_NR,
> +#endif
> +#ifdef CONFIG_KASAN
> + KASAN_SHADOW_START_NR,
> + KASAN_SHADOW_END_NR,
> +#endif
> + FIXMAP_START_NR,
> + FIXMAP_END_NR,
> + END_OF_SPACE_NR
> +};
> +
> +
> +
> +static struct addr_marker address_markers[] = {
> + {0, "PCI I/O start"},
> + {0, "PCI I/O end"},
> + {0, "modules start"},
> + {0, "modules end"},
> + {0, "vmalloc() area"},
> + {0, "vmalloc() end"},
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> + {0, "vmemmap start"},
> + {0, "vmemmap end"},
> +#endif
> +#ifdef CONFIG_KFENCE
> + {0, "kfence area start"},
> + {0, "kfence area end"},
> +#endif
> +#ifdef CONFIG_KASAN
> + {0, "Kasan shadow start"},
> + {0, "Kasan shadow end"},
> +#endif
> + {0, "Fixmap start"},
> + {0, "Fixmap end"},
> + {-1, NULL},
> +};
> +
> +
> +static struct ptd_mm_info kernel_ptd_info = {
> + .mm = &init_mm,
> + .markers = address_markers,
> + .base_addr = 0,
> + .end = ULONG_MAX,
> +};
> +
> +static const struct prot_bits pte_bits[] = {
> + {
> + .mask = _PAGE_VALID,
> + .val = _PAGE_VALID,
> + .set = "V",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_DIRTY,
> + .val = _PAGE_DIRTY,
> + .set = "D",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_PLV,
> + .val = _PAGE_PLV_VAL,
> + .set = "KERN",
> + .clear = "USR ",
> + }, {
> + .mask = _CACHE_MASK,
> + .val = _CACHE_MASK,
> + .set = " ",
> + .clear = "SUC",
> + }, {
> + .mask = _PAGE_GLOBAL,
> + .val = _PAGE_GLOBAL,
> + .set = "G",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_PRESENT,
> + .val = _PAGE_PRESENT,
> + .set = "P",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_WRITE,
> + .val = _PAGE_WRITE,
> + .set = "W",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_HGLOBAL,
> + .val = _PAGE_HGLOBAL,
> + .set = "HG",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_NO_READ,
> + .val = _PAGE_NO_READ,
> + .set = "NR",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_NO_EXEC,
> + .val = _PAGE_NO_EXEC,
> + .set = "NX",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_RPLV,
> + .val = _PAGE_RPLV,
> + .set = "RPLV",
> + .clear = " ",
> + }
> +};
> +
> +static struct pg_level pg_level[] = {
> + { /* pgd */
> + .name = "PGD",
> + }, { /* p4d */
> + .name = (CONFIG_PGTABLE_LEVELS > 4) ? "P4D" : "PGD",
> + }, { /* pud */
> + .name = (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD",
> + }, { /* pmd */
> + .name = (CONFIG_PGTABLE_LEVELS > 2) ? "PMD" : "PGD",
> + }, { /* pte */
> + .name = "PTE",
> + },
> +};
> +
> +static void dump_prot(struct pg_state *st)
> +{
> +
> + unsigned int i;
> +
> + for (i = 0; i < ARRAY_SIZE(pte_bits); i++) {
> + const char *s;
> +
> + if (pte_bits[i].mask == _CACHE_MASK) {
> + if ((st->current_prot & pte_bits[i].mask) == _CACHE_CC)
> + s = "CC ";
> + else if ((st->current_prot & pte_bits[i].mask) == _CACHE_WUC)
> + s = "WUC";
> + else
> + s = pte_bits[i].clear;
> + } else if (pte_bits[i].mask == _PAGE_GLOBAL) {
> + if ((st->current_prot & pte_bits[i].mask) == pte_bits[i].val) {
> + if (st->level != 4)
> + s = "PSE";
> + else
> + s = pte_bits[i].set;
> + } else {
> + s = pte_bits[i].clear;
> + }
> +
> + } else {
> + if ((st->current_prot & pte_bits[i].mask) == pte_bits[i].val)
> + s = pte_bits[i].set;
> + else
> + s = pte_bits[i].clear;
> + }
> +
> +
> + if (s)
> + pt_dump_seq_printf(st->seq, " %s", s);
> + }
> +
> +}
> +
> +
> +#ifdef CONFIG_64BIT
> +#define ADDR_FORMAT "0x%016lx"
> +#else
> +#define ADDR_FORMAT "0x%08lx"
> +#endif
> +static void dump_addr(struct pg_state *st, unsigned long addr)
> +{
> + static const char units[] = "KMGTPE";
> + const char *unit = units;
> + unsigned long delta;
> +
> + pt_dump_seq_printf(st->seq, ADDR_FORMAT "-" ADDR_FORMAT " ",
> + st->start_address, addr);
> +
> + pt_dump_seq_printf(st->seq, " " ADDR_FORMAT " ", st->start_pa);
> + delta = (addr - st->start_address) >> 10;
> +
> + while (!(delta & 1023) && unit[1]) {
> + delta >>= 10;
> + unit++;
> + }
> +
> + pt_dump_seq_printf(st->seq, "%9lu%c %s", delta, *unit,
> + pg_level[st->level].name);
> +}
> +
> +static void note_prot_wx(struct pg_state *st, unsigned long addr)
> +{
> + if (!st->check_wx)
> + return;
> + if ((st->current_prot & _PAGE_WRITE) == 0)
> + return;
> + if ((st->current_prot & _PAGE_NO_EXEC) == _PAGE_NO_EXEC)
> + return;
> +
> + st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
> +
> +}
> +
> +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);
> + u64 pa = PFN_PHYS(pte_pfn(__pte(val)));
> + u64 prot = 0;
> +
> + if (level >= 0)
> + prot = val & pg_level[level].mask;
> +
> + if (st->level == -1) {
> + st->level = level;
> + st->current_prot = prot;
> + st->start_address = addr;
> + st->start_pa = pa;
> + st->last_pa = pa;
> + 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) {
> + if (st->current_prot) {
> + note_prot_wx(st, addr);
> + dump_addr(st, addr);
> + dump_prot(st);
> + pt_dump_seq_puts(st->seq, "\n");
> + }
> +
> + while (addr >= st->marker[1].start_address) {
> + st->marker++;
> + pt_dump_seq_printf(st->seq, "---[ %s ]---\n",
> + st->marker->name);
> + }
> +
> + st->start_address = addr;
> + st->start_pa = pa;
> + st->last_pa = pa;
> + st->current_prot = prot;
> + st->level = level;
> + } else {
> + st->last_pa = pa;
> + }
> +}
> +
> +static void note_page_pte(struct ptdump_state *pt_st, unsigned long addr, pte_t pte)
> +{
> + note_page(pt_st, addr, 4, pte_val(pte));
> +}
> +
> +static void note_page_pmd(struct ptdump_state *pt_st, unsigned long addr, pmd_t pmd)
> +{
> + note_page(pt_st, addr, 3, pmd_val(pmd));
> +}
> +
> +static void note_page_pud(struct ptdump_state *pt_st, unsigned long addr, pud_t pud)
> +{
> + note_page(pt_st, addr, 2, pud_val(pud));
> +}
> +
> +static void note_page_p4d(struct ptdump_state *pt_st, unsigned long addr, p4d_t p4d)
> +{
> + note_page(pt_st, addr, 1, p4d_val(p4d));
> +}
> +
> +static void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd)
> +{
> + note_page(pt_st, addr, 0, pgd_val(pgd));
> +}
> +
> +static void note_page_flush(struct ptdump_state *pt_st)
> +{
> + pte_t pte_zero = {0};
> +
> + note_page(pt_st, 0, -1, pte_val(pte_zero));
> +}
> +
> +void ptdump_walk(struct seq_file *s, struct ptd_mm_info *pinfo)
> +{
> + struct pg_state st = {
> + .seq = s,
> + .marker = pinfo->markers,
> + .level = -1,
> + .ptdump = {
> + .note_page_pte = note_page_pte,
> + .note_page_pmd = note_page_pmd,
> + .note_page_pud = note_page_pud,
> + .note_page_p4d = note_page_p4d,
> + .note_page_pgd = note_page_pgd,
> + .note_page_flush = note_page_flush,
> + .range = (struct ptdump_range[]) {
> + {pinfo->base_addr, pinfo->end},
> + {0, 0}
> + }
> + }
> + };
> +
> + ptdump_walk_pgd(&st.ptdump, pinfo->mm, NULL);
> +}
> +
> +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_pte = note_page_pte,
> + .note_page_pmd = note_page_pmd,
> + .note_page_pud = note_page_pud,
> + .note_page_p4d = note_page_p4d,
> + .note_page_pgd = note_page_pgd,
> + .note_page_flush = note_page_flush,
> + .range = (struct ptdump_range[]) {
> + {vm_map_base, ULONG_MAX},
> + {0, 0}
> + }
> + }
> + };
> +
> + 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;
> + }
> +
> + pr_info("Checked W+X mappings: passed, no W+X pages found\n");
> +
> + return true;
> +}
> +
> +
> +static int __init ptdump_init(void)
> +{
> + unsigned int i, j;
> +
> + address_markers[PCI_IO_START_NR].start_address = (unsigned long)PCI_IOBASE;
> + address_markers[PCI_IO_END_NR].start_address = (unsigned long)PCI_IOBASE + IO_SPACE_LIMIT;
> +
> + address_markers[MODULES_START_NR].start_address = MODULES_VADDR;
> + address_markers[MODULES_END_NR].start_address = MODULES_END;
> +
> + address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
> + address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
> +
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> + address_markers[VMEMMAP_START_NR].start_address = (unsigned long)vmemmap;
> + address_markers[VMEMMAP_END_NR].start_address = VMEMMAP_END;
> +#endif
> +
> +#ifdef CONFIG_KFENCE
> + address_markers[KFENCE_AREA_START_NR].start_address = KFENCE_AREA_START;
> + address_markers[KFENCE_AREA_END_NR].start_address = KFENCE_AREA_END;
> +#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
> +
> + address_markers[FIXMAP_START_NR].start_address = FIXADDR_START;
> + address_markers[FIXMAP_END_NR].start_address = FIXADDR_TOP;
> +
> + kernel_ptd_info.base_addr = vm_map_base;
> +
> + for (i = 0; i < ARRAY_SIZE(pg_level); i++) {
> + for (j = 0; j < ARRAY_SIZE(pte_bits); j++)
> + pg_level[i].mask |= pte_bits[j].mask;
> + }
> +
> + ptdump_debugfs_register(&kernel_ptd_info, "kernel_page_tables");
> +
> + return 0;
> +}
> +
> +device_initcall(ptdump_init);
> diff --git a/arch/loongarch/mm/ptdump_debugfs.c b/arch/loongarch/mm/ptdump_debugfs.c
> new file mode 100644
> index 000000000000..aa6169f6aa3a
> --- /dev/null
> +++ b/arch/loongarch/mm/ptdump_debugfs.c
> @@ -0,0 +1,22 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/debugfs.h>
> +#include <linux/seq_file.h>
> +
> +#include <asm/ptdump.h>
> +#include <asm/pgtable.h>
> +#include <asm/kasan.h>
> +
> +static int ptdump_show(struct seq_file *m, void *v)
> +{
> + struct ptd_mm_info *info = m->private;
> +
> + ptdump_walk(m, info);
> + return 0;
> +}
> +DEFINE_SHOW_ATTRIBUTE(ptdump);
> +
> +void __init ptdump_debugfs_register(struct ptd_mm_info *info, const char *name)
> +{
> + debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
> +}
> +
> --
> 2.43.0
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] LoongArch: Add support to dump the kernel page tables
2026-06-29 14:00 ` Huacai Chen
@ 2026-06-30 12:09 ` haoran.jiang
0 siblings, 0 replies; 3+ messages in thread
From: haoran.jiang @ 2026-06-30 12:09 UTC (permalink / raw)
To: Huacai Chen
Cc: loongarch, linux-kernel, kernel, yangtiezhu, Haoran Jiang,
Xiujie Jiang
2026年6月29日 22:00, "Huacai Chen" <chenhuacai@kernel.org mailto:chenhuacai@kernel.org?to=%22Huacai%20Chen%22%20%3Cchenhuacai%40kernel.org%3E > 写到:
>
> Hi, Haoran,
>
> On Mon, Jun 29, 2026 at 3:44 PM <haoran.jiang@linux.dev> wrote:
>
> >
> > From: Haoran Jiang <jianghaoran@kylinos.cn>
> >
> > In a similar manner to riscv,arm64,x86 etc.,this patch allows
> > dumping the page tables of the LoongArch page-mapped virtual memory
> > region via a debugfs file, which is useful for kernel developers to
> > inspect page table layouts and verify permissions and type settings.
> >
> I like the RISC-V version that put everything in ptdump.c.
>
> Huacai
>
1，The ptdump functionality can be enabled via either CONFIG_PTDUMP_DEBUGFS
or CONFIG_DEBUG_WX. For example, RISC-V enables it through DEBUG_WX,
while other architectures support both options.
CONFIG_DEBUG_WX performs a kernel page table permission check at boot
time to enforce the W^X principle. It depends on CONFIG_STRICT_KERNEL_RWX;
debug_checkwx() is only invoked when CONFIG_STRICT_KERNEL_RWX is enabled.
However, on LoongArch, the kernel text segment resides in the direct
mapping region, where permission control cannot be enforced via page
tables. Therefore, CONFIG_STRICT_KERNEL_RWX is not necessary to
implement, and enabling DEBUG_WX is also unnecessary. Instead, this
patch adopts CONFIG_PTDUMP_DEBUGFS to enable the ptdump feature for
LoongArch.
2，However, for page-mapped regions, the page table permissions should conform to the W^X principle. The MODULES region can meet this requirement via `CONFIG_STRICT_MODULE_RWX`.But other regions, such as vmalloc, currently still do not comply with the W^X principle (as can be verified by checking `cat /sys/kernel/debug/check_wx_pages`). I intend to add `PAGE_NO_EXEC` to the `PAGE_KERNEL` definition。
#define PAGE_KERNEL __pgprot(_PAGE_PRESENT | __READABLE | __WRITEABLE | \___
__ PAGE_GLOBAL | _PAGE_KERN | _CACHE_CC | _PAGE_NO_EXEC)
#define PAGE_KERNEL_SUC __pgprot(_PAGE_PRESENT | __READABLE | __WRITEABLE | \
_PAGE_GLOBAL | _PAGE_KERN | _CACHE_SUC | _PAGE_NO_EXEC)
#define PAGE_KERNEL_WUC __pgprot(_PAGE_PRESENT | __READABLE | __WRITEABLE | \
PAGE_GLOBAL | _PAGE_KERN | _CACHE_WUC | _PAGE_NO_EXEC)
eBPF memory allocated from the MODULES region is not affected by this change, because it already gets executable permissions via `set_memory_rox`.
The vmalloc, PCI I/O, vmemmap, KFENCE, KASAN, and Fixmap regions should all be non-executable by default.
Would this modification have any other side effects?
thanks!
> >
> > Co-developed-by: Xiujie Jiang <jiangxiujie@kylinos.cn>
> > Signed-off-by: Xiujie Jiang <jiangxiujie@kylinos.cn>
> > Signed-off-by: Haoran Jiang <jianghaoran@kylinos.cn>
> > ---
> > arch/loongarch/Kconfig | 1 +
> > arch/loongarch/include/asm/ptdump.h | 61 ++++
> > arch/loongarch/mm/Makefile | 2 +
> > arch/loongarch/mm/ptdump.c | 417 ++++++++++++++++++++++++++++
> > arch/loongarch/mm/ptdump_debugfs.c | 22 ++
> > 5 files changed, 503 insertions(+)
> > create mode 100644 arch/loongarch/include/asm/ptdump.h
> > create mode 100644 arch/loongarch/mm/ptdump.c
> > create mode 100644 arch/loongarch/mm/ptdump_debugfs.c
> >
> > diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> > index bec7cc1d72ee..e97fe97e1955 100644
> > --- a/arch/loongarch/Kconfig
> > +++ b/arch/loongarch/Kconfig
> > @@ -25,6 +25,7 @@ config LOONGARCH
> > select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> > select ARCH_HAS_PREEMPT_LAZY
> > select ARCH_HAS_PTE_SPECIAL if 64BIT
> > + select ARCH_HAS_PTDUMP
> > select ARCH_HAS_SET_MEMORY
> > select ARCH_HAS_SET_DIRECT_MAP
> > select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
> > diff --git a/arch/loongarch/include/asm/ptdump.h b/arch/loongarch/include/asm/ptdump.h
> > new file mode 100644
> > index 000000000000..4590ea56abe6
> > --- /dev/null
> > +++ b/arch/loongarch/include/asm/ptdump.h
> > @@ -0,0 +1,61 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +
> > +#ifndef __ASM_PTDUMP_H
> > +#define __ASM_PTDUMP_H
> > +
> > +#include <linux/ptdump.h>
> > +#include <linux/mm_types.h>
> > +#include <linux/seq_file.h>
> > +
> > +/*
> > + * 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.
> > + */
> > +struct pg_state {
> > + struct ptdump_state ptdump;
> > + struct seq_file *seq;
> > + const struct addr_marker *marker;
> > + unsigned long start_address;
> > + unsigned long start_pa;
> > + unsigned long last_pa;
> > + int level;
> > + u64 current_prot;
> > + bool check_wx;
> > + unsigned long wx_pages;
> > +};
> > +
> > +/* Address marker */
> > +struct addr_marker {
> > + unsigned long start_address;
> > + const char *name;
> > +};
> > +
> > +/* Private information for debugfs */
> > +struct ptd_mm_info {
> > + struct mm_struct *mm;
> > + const struct addr_marker *markers;
> > + unsigned long base_addr;
> > + unsigned long end;
> > +};
> > +
> > +/* Page Table Entry */
> > +struct prot_bits {
> > + u64 mask;
> > + u64 val;
> > + const char *set;
> > + const char *clear;
> > +};
> > +
> > +/* Page Level */
> > +struct pg_level {
> > + const char *name;
> > + u64 mask;
> > +};
> > +
> > +void ptdump_walk(struct seq_file *s, struct ptd_mm_info *pinfo);
> > +void __init ptdump_debugfs_register(struct ptd_mm_info *info, const char *name);
> > +
> > +#endif /* __ASM_PTDUMP_H */
> > +
> > diff --git a/arch/loongarch/mm/Makefile b/arch/loongarch/mm/Makefile
> > index 2aae3773de77..da9e6fee0439 100644
> > --- a/arch/loongarch/mm/Makefile
> > +++ b/arch/loongarch/mm/Makefile
> > @@ -10,5 +10,7 @@ obj-y += init.o cache.o tlb.o tlbex.o extable.o \
> > obj-$(CONFIG_HIGHMEM) += highmem.o
> > obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
> > obj-$(CONFIG_KASAN) += kasan_init.o
> > +obj-$(CONFIG_PTDUMP) += ptdump.o
> > +obj-$(CONFIG_PTDUMP_DEBUGFS) += ptdump_debugfs.o
> >
> > KASAN_SANITIZE_kasan_init.o := n
> > diff --git a/arch/loongarch/mm/ptdump.c b/arch/loongarch/mm/ptdump.c
> > new file mode 100644
> > index 000000000000..cab6dad18150
> > --- /dev/null
> > +++ b/arch/loongarch/mm/ptdump.c
> > @@ -0,0 +1,417 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Derived from riscv implementation
> > + */
> > +
> > +#include <linux/init.h>
> > +#include <linux/debugfs.h>
> > +#include <linux/seq_file.h>
> > +#include <linux/ptdump.h>
> > +#include <linux/pgtable.h>
> > +#include <asm/kasan.h>
> > +#include <asm/ptdump.h>
> > +
> > +#define _PAGE_PLV_VAL 0x0
> > +
> > +#define pt_dump_seq_printf(m, fmt, args...) \
> > +({ \
> > + if (m) \
> > + seq_printf(m, fmt, ##args); \
> > +})
> > +
> > +#define pt_dump_seq_puts(m, fmt) \
> > +({ \
> > + if (m) \
> > + seq_puts(m, fmt); \
> > +})
> > +
> > +enum address_markers_idx {
> > + PCI_IO_START_NR,
> > + PCI_IO_END_NR,
> > + MODULES_START_NR,
> > + MODULES_END_NR,
> > + VMALLOC_START_NR,
> > + VMALLOC_END_NR,
> > +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> > + VMEMMAP_START_NR,
> > + VMEMMAP_END_NR,
> > +#endif
> > +#ifdef CONFIG_KFENCE
> > + KFENCE_AREA_START_NR,
> > + KFENCE_AREA_END_NR,
> > +#endif
> > +#ifdef CONFIG_KASAN
> > + KASAN_SHADOW_START_NR,
> > + KASAN_SHADOW_END_NR,
> > +#endif
> > + FIXMAP_START_NR,
> > + FIXMAP_END_NR,
> > + END_OF_SPACE_NR
> > +};
> > +
> > +
> > +
> > +static struct addr_marker address_markers[] = {
> > + {0, "PCI I/O start"},
> > + {0, "PCI I/O end"},
> > + {0, "modules start"},
> > + {0, "modules end"},
> > + {0, "vmalloc() area"},
> > + {0, "vmalloc() end"},
> > +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> > + {0, "vmemmap start"},
> > + {0, "vmemmap end"},
> > +#endif
> > +#ifdef CONFIG_KFENCE
> > + {0, "kfence area start"},
> > + {0, "kfence area end"},
> > +#endif
> > +#ifdef CONFIG_KASAN
> > + {0, "Kasan shadow start"},
> > + {0, "Kasan shadow end"},
> > +#endif
> > + {0, "Fixmap start"},
> > + {0, "Fixmap end"},
> > + {-1, NULL},
> > +};
> > +
> > +
> > +static struct ptd_mm_info kernel_ptd_info = {
> > + .mm = &init_mm,
> > + .markers = address_markers,
> > + .base_addr = 0,
> > + .end = ULONG_MAX,
> > +};
> > +
> > +static const struct prot_bits pte_bits[] = {
> > + {
> > + .mask = _PAGE_VALID,
> > + .val = _PAGE_VALID,
> > + .set = "V",
> > + .clear = " ",
> > + }, {
> > + .mask = _PAGE_DIRTY,
> > + .val = _PAGE_DIRTY,
> > + .set = "D",
> > + .clear = " ",
> > + }, {
> > + .mask = _PAGE_PLV,
> > + .val = _PAGE_PLV_VAL,
> > + .set = "KERN",
> > + .clear = "USR ",
> > + }, {
> > + .mask = _CACHE_MASK,
> > + .val = _CACHE_MASK,
> > + .set = " ",
> > + .clear = "SUC",
> > + }, {
> > + .mask = _PAGE_GLOBAL,
> > + .val = _PAGE_GLOBAL,
> > + .set = "G",
> > + .clear = " ",
> > + }, {
> > + .mask = _PAGE_PRESENT,
> > + .val = _PAGE_PRESENT,
> > + .set = "P",
> > + .clear = " ",
> > + }, {
> > + .mask = _PAGE_WRITE,
> > + .val = _PAGE_WRITE,
> > + .set = "W",
> > + .clear = " ",
> > + }, {
> > + .mask = _PAGE_HGLOBAL,
> > + .val = _PAGE_HGLOBAL,
> > + .set = "HG",
> > + .clear = " ",
> > + }, {
> > + .mask = _PAGE_NO_READ,
> > + .val = _PAGE_NO_READ,
> > + .set = "NR",
> > + .clear = " ",
> > + }, {
> > + .mask = _PAGE_NO_EXEC,
> > + .val = _PAGE_NO_EXEC,
> > + .set = "NX",
> > + .clear = " ",
> > + }, {
> > + .mask = _PAGE_RPLV,
> > + .val = _PAGE_RPLV,
> > + .set = "RPLV",
> > + .clear = " ",
> > + }
> > +};
> > +
> > +static struct pg_level pg_level[] = {
> > + { /* pgd */
> > + .name = "PGD",
> > + }, { /* p4d */
> > + .name = (CONFIG_PGTABLE_LEVELS > 4) ? "P4D" : "PGD",
> > + }, { /* pud */
> > + .name = (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD",
> > + }, { /* pmd */
> > + .name = (CONFIG_PGTABLE_LEVELS > 2) ? "PMD" : "PGD",
> > + }, { /* pte */
> > + .name = "PTE",
> > + },
> > +};
> > +
> > +static void dump_prot(struct pg_state *st)
> > +{
> > +
> > + unsigned int i;
> > +
> > + for (i = 0; i < ARRAY_SIZE(pte_bits); i++) {
> > + const char *s;
> > +
> > + if (pte_bits[i].mask == _CACHE_MASK) {
> > + if ((st->current_prot & pte_bits[i].mask) == _CACHE_CC)
> > + s = "CC ";
> > + else if ((st->current_prot & pte_bits[i].mask) == _CACHE_WUC)
> > + s = "WUC";
> > + else
> > + s = pte_bits[i].clear;
> > + } else if (pte_bits[i].mask == _PAGE_GLOBAL) {
> > + if ((st->current_prot & pte_bits[i].mask) == pte_bits[i].val) {
> > + if (st->level != 4)
> > + s = "PSE";
> > + else
> > + s = pte_bits[i].set;
> > + } else {
> > + s = pte_bits[i].clear;
> > + }
> > +
> > + } else {
> > + if ((st->current_prot & pte_bits[i].mask) == pte_bits[i].val)
> > + s = pte_bits[i].set;
> > + else
> > + s = pte_bits[i].clear;
> > + }
> > +
> > +
> > + if (s)
> > + pt_dump_seq_printf(st->seq, " %s", s);
> > + }
> > +
> > +}
> > +
> > +
> > +#ifdef CONFIG_64BIT
> > +#define ADDR_FORMAT "0x%016lx"
> > +#else
> > +#define ADDR_FORMAT "0x%08lx"
> > +#endif
> > +static void dump_addr(struct pg_state *st, unsigned long addr)
> > +{
> > + static const char units[] = "KMGTPE";
> > + const char *unit = units;
> > + unsigned long delta;
> > +
> > + pt_dump_seq_printf(st->seq, ADDR_FORMAT "-" ADDR_FORMAT " ",
> > + st->start_address, addr);
> > +
> > + pt_dump_seq_printf(st->seq, " " ADDR_FORMAT " ", st->start_pa);
> > + delta = (addr - st->start_address) >> 10;
> > +
> > + while (!(delta & 1023) && unit[1]) {
> > + delta >>= 10;
> > + unit++;
> > + }
> > +
> > + pt_dump_seq_printf(st->seq, "%9lu%c %s", delta, *unit,
> > + pg_level[st->level].name);
> > +}
> > +
> > +static void note_prot_wx(struct pg_state *st, unsigned long addr)
> > +{
> > + if (!st->check_wx)
> > + return;
> > + if ((st->current_prot & _PAGE_WRITE) == 0)
> > + return;
> > + if ((st->current_prot & _PAGE_NO_EXEC) == _PAGE_NO_EXEC)
> > + return;
> > +
> > + st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
> > +
> > +}
> > +
> > +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);
> > + u64 pa = PFN_PHYS(pte_pfn(__pte(val)));
> > + u64 prot = 0;
> > +
> > + if (level >= 0)
> > + prot = val & pg_level[level].mask;
> > +
> > + if (st->level == -1) {
> > + st->level = level;
> > + st->current_prot = prot;
> > + st->start_address = addr;
> > + st->start_pa = pa;
> > + st->last_pa = pa;
> > + 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) {
> > + if (st->current_prot) {
> > + note_prot_wx(st, addr);
> > + dump_addr(st, addr);
> > + dump_prot(st);
> > + pt_dump_seq_puts(st->seq, "\n");
> > + }
> > +
> > + while (addr >= st->marker[1].start_address) {
> > + st->marker++;
> > + pt_dump_seq_printf(st->seq, "---[ %s ]---\n",
> > + st->marker->name);
> > + }
> > +
> > + st->start_address = addr;
> > + st->start_pa = pa;
> > + st->last_pa = pa;
> > + st->current_prot = prot;
> > + st->level = level;
> > + } else {
> > + st->last_pa = pa;
> > + }
> > +}
> > +
> > +static void note_page_pte(struct ptdump_state *pt_st, unsigned long addr, pte_t pte)
> > +{
> > + note_page(pt_st, addr, 4, pte_val(pte));
> > +}
> > +
> > +static void note_page_pmd(struct ptdump_state *pt_st, unsigned long addr, pmd_t pmd)
> > +{
> > + note_page(pt_st, addr, 3, pmd_val(pmd));
> > +}
> > +
> > +static void note_page_pud(struct ptdump_state *pt_st, unsigned long addr, pud_t pud)
> > +{
> > + note_page(pt_st, addr, 2, pud_val(pud));
> > +}
> > +
> > +static void note_page_p4d(struct ptdump_state *pt_st, unsigned long addr, p4d_t p4d)
> > +{
> > + note_page(pt_st, addr, 1, p4d_val(p4d));
> > +}
> > +
> > +static void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd)
> > +{
> > + note_page(pt_st, addr, 0, pgd_val(pgd));
> > +}
> > +
> > +static void note_page_flush(struct ptdump_state *pt_st)
> > +{
> > + pte_t pte_zero = {0};
> > +
> > + note_page(pt_st, 0, -1, pte_val(pte_zero));
> > +}
> > +
> > +void ptdump_walk(struct seq_file *s, struct ptd_mm_info *pinfo)
> > +{
> > + struct pg_state st = {
> > + .seq = s,
> > + .marker = pinfo->markers,
> > + .level = -1,
> > + .ptdump = {
> > + .note_page_pte = note_page_pte,
> > + .note_page_pmd = note_page_pmd,
> > + .note_page_pud = note_page_pud,
> > + .note_page_p4d = note_page_p4d,
> > + .note_page_pgd = note_page_pgd,
> > + .note_page_flush = note_page_flush,
> > + .range = (struct ptdump_range[]) {
> > + {pinfo->base_addr, pinfo->end},
> > + {0, 0}
> > + }
> > + }
> > + };
> > +
> > + ptdump_walk_pgd(&st.ptdump, pinfo->mm, NULL);
> > +}
> > +
> > +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_pte = note_page_pte,
> > + .note_page_pmd = note_page_pmd,
> > + .note_page_pud = note_page_pud,
> > + .note_page_p4d = note_page_p4d,
> > + .note_page_pgd = note_page_pgd,
> > + .note_page_flush = note_page_flush,
> > + .range = (struct ptdump_range[]) {
> > + {vm_map_base, ULONG_MAX},
> > + {0, 0}
> > + }
> > + }
> > + };
> > +
> > + 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;
> > + }
> > +
> > + pr_info("Checked W+X mappings: passed, no W+X pages found\n");
> > +
> > + return true;
> > +}
> > +
> > +
> > +static int __init ptdump_init(void)
> > +{
> > + unsigned int i, j;
> > +
> > + address_markers[PCI_IO_START_NR].start_address = (unsigned long)PCI_IOBASE;
> > + address_markers[PCI_IO_END_NR].start_address = (unsigned long)PCI_IOBASE + IO_SPACE_LIMIT;
> > +
> > + address_markers[MODULES_START_NR].start_address = MODULES_VADDR;
> > + address_markers[MODULES_END_NR].start_address = MODULES_END;
> > +
> > + address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
> > + address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
> > +
> > +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> > + address_markers[VMEMMAP_START_NR].start_address = (unsigned long)vmemmap;
> > + address_markers[VMEMMAP_END_NR].start_address = VMEMMAP_END;
> > +#endif
> > +
> > +#ifdef CONFIG_KFENCE
> > + address_markers[KFENCE_AREA_START_NR].start_address = KFENCE_AREA_START;
> > + address_markers[KFENCE_AREA_END_NR].start_address = KFENCE_AREA_END;
> > +#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
> > +
> > + address_markers[FIXMAP_START_NR].start_address = FIXADDR_START;
> > + address_markers[FIXMAP_END_NR].start_address = FIXADDR_TOP;
> > +
> > + kernel_ptd_info.base_addr = vm_map_base;
> > +
> > + for (i = 0; i < ARRAY_SIZE(pg_level); i++) {
> > + for (j = 0; j < ARRAY_SIZE(pte_bits); j++)
> > + pg_level[i].mask |= pte_bits[j].mask;
> > + }
> > +
> > + ptdump_debugfs_register(&kernel_ptd_info, "kernel_page_tables");
> > +
> > + return 0;
> > +}
> > +
> > +device_initcall(ptdump_init);
> > diff --git a/arch/loongarch/mm/ptdump_debugfs.c b/arch/loongarch/mm/ptdump_debugfs.c
> > new file mode 100644
> > index 000000000000..aa6169f6aa3a
> > --- /dev/null
> > +++ b/arch/loongarch/mm/ptdump_debugfs.c
> > @@ -0,0 +1,22 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include <linux/debugfs.h>
> > +#include <linux/seq_file.h>
> > +
> > +#include <asm/ptdump.h>
> > +#include <asm/pgtable.h>
> > +#include <asm/kasan.h>
> > +
> > +static int ptdump_show(struct seq_file *m, void *v)
> > +{
> > + struct ptd_mm_info *info = m->private;
> > +
> > + ptdump_walk(m, info);
> > + return 0;
> > +}
> > +DEFINE_SHOW_ATTRIBUTE(ptdump);
> > +
> > +void __init ptdump_debugfs_register(struct ptd_mm_info *info, const char *name)
> > +{
> > + debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
> > +}
> > +
> > --
> > 2.43.0
> >
>
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2026-06-29 7:43 [PATCH] LoongArch: Add support to dump the kernel page tables haoran.jiang
2026-06-29 14:00 ` Huacai Chen
2026-06-30 12:09 ` haoran.jiang
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