[kernel-hardening] [RFC 2/7] init: add set_ro_mostly_after_init_rw/ro function

Hoeun Ryu
2017-02-19T10:04:05Z

Add set_ro_mostly_after_init_rw/ro pair to modify memory attributes for
memory marked as `ro_mostly_after_init`.

I am doubtful that this is the right place where these functions reside and
these functions are suitable for all architectures for memory attributes
modification. Please comment.

Signed-off-by: Hoeun Ryu <hoeun.ryu@gmail.com>
---
include/linux/init.h | 6 ++++++
init/main.c | 24 ++++++++++++++++++++++++
2 files changed, 30 insertions(+)

diff --git a/include/linux/init.h b/include/linux/init.h
index 79af096..d68e4f7 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -131,6 +131,12 @@ extern bool rodata_enabled;
#endif
#ifdef CONFIG_STRICT_KERNEL_RWX
void mark_rodata_ro(void);
+
+void set_ro_mostly_after_init_rw(void);
+void set_ro_mostly_after_init_ro(void);
+#else
+static inline void set_ro_mostly_after_init_rw(void) { }
+static inline void set_ro_mostly_after_init_ro(void) { }
#endif

extern void (*late_time_init)(void);
diff --git a/init/main.c b/init/main.c
index 4719abf..a5d4873 100644
--- a/init/main.c
+++ b/init/main.c
@@ -941,6 +941,30 @@ static void mark_readonly(void)
} else
pr_info("Kernel memory protection disabled.\n");
}
+
+void set_ro_mostly_after_init_rw(void)
+{
+ unsigned long start = PFN_ALIGN(__start_data_ro_mostly_after_init);
+ unsigned long end = PFN_ALIGN(&__end_data_ro_mostly_after_init);
+ unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
+
+ if (!rodata_enabled)
+ return;
+
+ set_memory_rw(start, nr_pages);
+}
+
+void set_ro_mostly_after_init_ro(void)
+{
+ unsigned long start = PFN_ALIGN(__start_data_ro_mostly_after_init);
+ unsigned long end = PFN_ALIGN(&__end_data_ro_mostly_after_init);
+ unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
+
+ if (!rodata_enabled)
+ return;
+
+ set_memory_ro(start, nr_pages);
+}
#else
static inline void mark_readonly(void)
{
--
2.7.4