[PATCH] x86, kernel: make X86_PTDUMP a tristate

* [PATCH] x86, kernel: make X86_PTDUMP a tristate
@ 2015-11-20  1:07 Kees Cook
  2015-11-23 16:29 ` [tip:x86/mm] x86/mm: Turn CONFIG_X86_PTDUMP into a module tip-bot for Kees Cook
  0 siblings, 1 reply; 2+ messages in thread
From: Kees Cook @ 2015-11-20  1:07 UTC (permalink / raw)
  To: linux-kernel
  Cc: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, x86, Andrew Morton,
	Will Deacon, Stephen Smalley, Andrey Ryabinin, Vladimir Murzin,
	Toshi Kani, Boris Ostrovsky

Being able to examine page tables is handy, so make this a module that
can be loaded as needed.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/Kconfig.debug         |  2 +-
 arch/x86/mm/Makefile           |  1 +
 arch/x86/mm/debug_pagetables.c | 46 ++++++++++++++++++++++++++++++++++++++++++
 arch/x86/mm/dump_pagetables.c  | 34 ++-----------------------------
 4 files changed, 50 insertions(+), 33 deletions(-)
 create mode 100644 arch/x86/mm/debug_pagetables.c

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 137dfa96aa14..110253ce83af 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -69,7 +69,7 @@ config X86_PTDUMP_CORE
 	def_bool n
 
 config X86_PTDUMP
-	bool "Export kernel pagetable layout to userspace via debugfs"
+	tristate "Export kernel pagetable layout to userspace via debugfs"
 	depends on DEBUG_KERNEL
 	select DEBUG_FS
 	select X86_PTDUMP_CORE
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 65c47fda26fc..f9d38a48e3c8 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -15,6 +15,7 @@ obj-$(CONFIG_X86_32)		+= pgtable_32.o iomap_32.o
 
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
 obj-$(CONFIG_X86_PTDUMP_CORE)	+= dump_pagetables.o
+obj-$(CONFIG_X86_PTDUMP)	+= debug_pagetables.o
 
 obj-$(CONFIG_HIGHMEM)		+= highmem_32.o
 
diff --git a/arch/x86/mm/debug_pagetables.c b/arch/x86/mm/debug_pagetables.c
new file mode 100644
index 000000000000..b35ee86a9316
--- /dev/null
+++ b/arch/x86/mm/debug_pagetables.c
@@ -0,0 +1,46 @@
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <asm/pgtable.h>
+
+static int ptdump_show(struct seq_file *m, void *v)
+{
+	ptdump_walk_pgd_level(m, NULL);
+	return 0;
+}
+
+static int ptdump_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, ptdump_show, NULL);
+}
+
+static const struct file_operations ptdump_fops = {
+	.owner		= THIS_MODULE,
+	.open		= ptdump_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+static struct dentry *pe;
+
+static int __init pt_dump_debug_init(void)
+{
+	pe = debugfs_create_file("kernel_page_tables", 0600, NULL, NULL,
+				 &ptdump_fops);
+	if (!pe)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void __exit pt_dump_debug_exit(void)
+{
+	debugfs_remove_recursive(pe);
+}
+
+module_init(pt_dump_debug_init);
+module_exit(pt_dump_debug_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
+MODULE_DESCRIPTION("Kernel debugging helper that dumps pagetables");
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index a035c2aa7801..90a1dc054873 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -426,38 +426,15 @@ void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
 {
 	ptdump_walk_pgd_level_core(m, pgd, false);
 }
+EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level);
 
 void ptdump_walk_pgd_level_checkwx(void)
 {
 	ptdump_walk_pgd_level_core(NULL, NULL, true);
 }
 
-#ifdef CONFIG_X86_PTDUMP
-static int ptdump_show(struct seq_file *m, void *v)
+static int __init pt_dump_init(void)
 {
-	ptdump_walk_pgd_level(m, NULL);
-	return 0;
-}
-
-static int ptdump_open(struct inode *inode, struct file *filp)
-{
-	return single_open(filp, ptdump_show, NULL);
-}
-
-static const struct file_operations ptdump_fops = {
-	.open		= ptdump_open,
-	.read		= seq_read,
-	.llseek		= seq_lseek,
-	.release	= single_release,
-};
-#endif
-
-static int pt_dump_init(void)
-{
-#ifdef CONFIG_X86_PTDUMP
-	struct dentry *pe;
-#endif
-
 #ifdef CONFIG_X86_32
 	/* Not a compile-time constant on x86-32 */
 	address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
@@ -468,13 +445,6 @@ static int pt_dump_init(void)
 	address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
 #endif
 
-#ifdef CONFIG_X86_PTDUMP
-	pe = debugfs_create_file("kernel_page_tables", 0600, NULL, NULL,
-				 &ptdump_fops);
-	if (!pe)
-		return -ENOMEM;
-#endif
-
 	return 0;
 }
 
-- 
1.9.1


-- 
Kees Cook
Chrome OS Security

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