ARM: 8735/1: 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"))

Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Laura Abbott <labbott@redhat.com>
Reviewed-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Jinbum Park <jinb.park7@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

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

arch/arm/include/asm/ptdump.h

@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2014 ARM Ltd. */
+#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 */

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
 

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);

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;
+
+}