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Message-ID: <20151120010755.GA9060@www.outflux.net>
Date: Thu, 19 Nov 2015 17:07:55 -0800
From: Kees Cook <keescook@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Will Deacon <will.deacon@....com>,
Stephen Smalley <sds@...ho.nsa.gov>,
Andrey Ryabinin <ryabinin.a.a@...il.com>,
Vladimir Murzin <vladimir.murzin@....com>,
Toshi Kani <toshi.kani@....com>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: [PATCH] x86, kernel: make X86_PTDUMP a tristate
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@...omium.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@...ux.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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