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Subject[kernel-hardening][PATCH v5 1/3] arm: mm: dump: make page table dumping reusable
This patch refactors the arm page table dumping code,
so multiple tables may be registered with the framework.

This patch refers below commits of arm64.
(4674fdb9f149 ("arm64: mm: dump: make page table dumping reusable"))
(4ddb9bf83349 ("arm64: dump: Make ptdump debugfs a separate option"))

Tested-by: Laura Abbott <labbott@redhat.com>
Reviewed-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Jinbum Park <jinb.park7@gmail.com>
---
v5: No changes
(Just add Tested-by, Reviewed-by from Laura Abbott)
---
arch/arm/Kconfig.debug | 6 +++-
arch/arm/include/asm/ptdump.h | 48 ++++++++++++++++++++++++++++++++
arch/arm/mm/Makefile | 3 +-
arch/arm/mm/dump.c | 65 +++++++++++++++++++------------------------
arch/arm/mm/ptdump_debugfs.c | 34 ++++++++++++++++++++++
5 files changed, 117 insertions(+), 39 deletions(-)
create mode 100644 arch/arm/include/asm/ptdump.h
create mode 100644 arch/arm/mm/ptdump_debugfs.c

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 17685e1..e7b94db 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -3,10 +3,14 @@ menu "Kernel hacking"

source "lib/Kconfig.debug"

-config ARM_PTDUMP
+config ARM_PTDUMP_CORE
+ def_bool n
+
+config ARM_PTDUMP_DEBUGFS
bool "Export kernel pagetable layout to userspace via debugfs"
depends on DEBUG_KERNEL
depends on MMU
+ select ARM_PTDUMP_CORE
select DEBUG_FS
---help---
Say Y here if you want to show the kernel pagetable layout in a
diff --git a/arch/arm/include/asm/ptdump.h b/arch/arm/include/asm/ptdump.h
new file mode 100644
index 0000000..3a6c0b7
--- /dev/null
+++ b/arch/arm/include/asm/ptdump.h
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2014 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_PTDUMP_H
+#define __ASM_PTDUMP_H
+
+#ifdef CONFIG_ARM_PTDUMP_CORE
+
+#include <linux/mm_types.h>
+#include <linux/seq_file.h>
+
+struct addr_marker {
+ unsigned long start_address;
+ char *name;
+};
+
+struct ptdump_info {
+ struct mm_struct *mm;
+ const struct addr_marker *markers;
+ unsigned long base_addr;
+};
+
+void ptdump_walk_pgd(struct seq_file *s, struct ptdump_info *info);
+#ifdef CONFIG_ARM_PTDUMP_DEBUGFS
+int ptdump_debugfs_register(struct ptdump_info *info, const char *name);
+#else
+static inline int ptdump_debugfs_register(struct ptdump_info *info,
+ const char *name)
+{
+ return 0;
+}
+#endif /* CONFIG_ARM_PTDUMP_DEBUGFS */
+
+#endif /* CONFIG_ARM_PTDUMP_CORE */
+
+#endif /* __ASM_PTDUMP_H */
diff --git a/arch/arm/mm/Makefile b/arch/arm/mm/Makefile
index 01bcc33..28be5f4 100644
--- a/arch/arm/mm/Makefile
+++ b/arch/arm/mm/Makefile
@@ -13,7 +13,8 @@ obj-y += nommu.o
obj-$(CONFIG_ARM_MPU) += pmsa-v7.o
endif

-obj-$(CONFIG_ARM_PTDUMP) += dump.o
+obj-$(CONFIG_ARM_PTDUMP_CORE) += dump.o
+obj-$(CONFIG_ARM_PTDUMP_DEBUGFS) += ptdump_debugfs.o
obj-$(CONFIG_MODULES) += proc-syms.o
obj-$(CONFIG_DEBUG_VIRTUAL) += physaddr.o

diff --git a/arch/arm/mm/dump.c b/arch/arm/mm/dump.c
index fc3b440..8dfe7c3 100644
--- a/arch/arm/mm/dump.c
+++ b/arch/arm/mm/dump.c
@@ -21,11 +21,7 @@
#include <asm/fixmap.h>
#include <asm/memory.h>
#include <asm/pgtable.h>
-
-struct addr_marker {
- unsigned long start_address;
- const char *name;
-};
+#include <asm/ptdump.h>

static struct addr_marker address_markers[] = {
{ MODULES_VADDR, "Modules" },
@@ -335,50 +331,36 @@ static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)
}
}

-static void walk_pgd(struct seq_file *m)
+static void walk_pgd(struct pg_state *st, struct mm_struct *mm,
+ unsigned long start)
{
- pgd_t *pgd = swapper_pg_dir;
- struct pg_state st;
- unsigned long addr;
+ pgd_t *pgd = pgd_offset(mm, 0UL);
unsigned i;
-
- memset(&st, 0, sizeof(st));
- st.seq = m;
- st.marker = address_markers;
+ unsigned long addr;

for (i = 0; i < PTRS_PER_PGD; i++, pgd++) {
- addr = i * PGDIR_SIZE;
+ addr = start + i * PGDIR_SIZE;
if (!pgd_none(*pgd)) {
- walk_pud(&st, pgd, addr);
+ walk_pud(st, pgd, addr);
} else {
- note_page(&st, addr, 1, pgd_val(*pgd), NULL);
+ note_page(st, addr, 1, pgd_val(*pgd), NULL);
}
}
-
- note_page(&st, 0, 0, 0, NULL);
}

-static int ptdump_show(struct seq_file *m, void *v)
+void ptdump_walk_pgd(struct seq_file *m, struct ptdump_info *info)
{
- walk_pgd(m);
- return 0;
-}
+ struct pg_state st = {
+ .seq = m,
+ .marker = info->markers,
+ };

-static int ptdump_open(struct inode *inode, struct file *file)
-{
- return single_open(file, ptdump_show, NULL);
+ walk_pgd(&st, info->mm, info->base_addr);
+ note_page(&st, 0, 0, 0, NULL);
}

-static const struct file_operations ptdump_fops = {
- .open = ptdump_open,
- .read = seq_read,
- .llseek = seq_lseek,
- .release = single_release,
-};
-
-static int ptdump_init(void)
+static void ptdump_initialize(void)
{
- struct dentry *pe;
unsigned i, j;

for (i = 0; i < ARRAY_SIZE(pg_level); i++)
@@ -387,9 +369,18 @@ static int ptdump_init(void)
pg_level[i].mask |= pg_level[i].bits[j].mask;

address_markers[2].start_address = VMALLOC_START;
+}

- pe = debugfs_create_file("kernel_page_tables", 0400, NULL, NULL,
- &ptdump_fops);
- return pe ? 0 : -ENOMEM;
+static struct ptdump_info kernel_ptdump_info = {
+ .mm = &init_mm,
+ .markers = address_markers,
+ .base_addr = 0,
+};
+
+static int ptdump_init(void)
+{
+ ptdump_initialize();
+ return ptdump_debugfs_register(&kernel_ptdump_info,
+ "kernel_page_tables");
}
__initcall(ptdump_init);
diff --git a/arch/arm/mm/ptdump_debugfs.c b/arch/arm/mm/ptdump_debugfs.c
new file mode 100644
index 0000000..be8d87b
--- /dev/null
+++ b/arch/arm/mm/ptdump_debugfs.c
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+
+#include <asm/ptdump.h>
+
+static int ptdump_show(struct seq_file *m, void *v)
+{
+ struct ptdump_info *info = m->private;
+
+ ptdump_walk_pgd(m, info);
+ return 0;
+}
+
+static int ptdump_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, ptdump_show, inode->i_private);
+}
+
+static const struct file_operations ptdump_fops = {
+ .open = ptdump_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+int ptdump_debugfs_register(struct ptdump_info *info, const char *name)
+{
+ struct dentry *pe;
+
+ pe = debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
+ return pe ? 0 : -ENOMEM;
+
+}
--
1.9.1
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