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Subject[PATCH] x86, kernel: make dump_pagetables 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@chromium.org>
---
arch/x86/Kconfig.debug | 2 +-
arch/x86/kernel/head.c | 6 ++++++
arch/x86/mm/dump_pagetables.c | 13 ++++++++++---
3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index c198b7e..a43b7ca 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -70,7 +70,7 @@ config DEBUG_STACKOVERFLOW
If in doubt, say "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
---help---
diff --git a/arch/x86/kernel/head.c b/arch/x86/kernel/head.c
index 992f442..871c0ca 100644
--- a/arch/x86/kernel/head.c
+++ b/arch/x86/kernel/head.c
@@ -69,3 +69,9 @@ void __init reserve_ebda_region(void)
/* reserve all memory between lowmem and the 1MB mark */
memblock_reserve(lowmem, 0x100000 - lowmem);
}
+
+#ifdef CONFIG_X86_64
+EXPORT_SYMBOL_GPL(init_level4_pgt);
+#else
+EXPORT_SYMBOL_GPL(swapper_pg_dir);
+#endif
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 0002a3a..7a54145 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -340,6 +340,8 @@ static int ptdump_open(struct inode *inode, struct file *filp)
return single_open(filp, ptdump_show, NULL);
}

+static struct dentry *pe;
+
static const struct file_operations ptdump_fops = {
.open = ptdump_open,
.read = seq_read,
@@ -347,9 +349,8 @@ static const struct file_operations ptdump_fops = {
.release = single_release,
};

-static int pt_dump_init(void)
+static int __init pt_dump_init(void)
{
- struct dentry *pe;

#ifdef CONFIG_X86_32
/* Not a compile-time constant on x86-32 */
@@ -369,7 +370,13 @@ static int pt_dump_init(void)
return 0;
}

-__initcall(pt_dump_init);
+static void __exit pt_dump_exit(void)
+{
+ debugfs_remove_recursive(pe);
+}
+
+module_init(pt_dump_init);
+module_exit(pt_dump_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
MODULE_DESCRIPTION("Kernel debugging helper that dumps pagetables");
--
1.7.9.5

--
Kees Cook
Chrome OS Security


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