[PATCH 5/5] ftrace, x86: do not depend on system state for kernel text info

[Steven Rostedt]

From: Steven Rostedt <srostedt@xxxxxxxxxx>

Andrew Morton pointed out that using SYSTEM_STATE is a bad idea
since there is no guarantee to what its state will actually be.

Instead, I moved the check into the set_kernel_text_* functions
themselves, and use a local variable to determine when it is
OK to change the kernel text RW permissions.

Reported-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
---
 arch/x86/kernel/ftrace.c |    8 --------
 arch/x86/mm/init_32.c    |   10 ++++++++++
 arch/x86/mm/init_64.c    |   10 ++++++++++
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index c9ba2f9..025d783 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -28,20 +28,12 @@
 
 int ftrace_arch_modify_prepare(void)
 {
-	/* at boot up, we are still writable */
-	if (system_state != SYSTEM_RUNNING)
-		return 0;
-
 	set_kernel_text_rw();
 	return 0;
 }
 
 int ftrace_arch_modify_post_process(void)
 {
-	/* at boot up, we are still writable */
-	if (system_state != SYSTEM_RUNNING)
-		return 0;
-
 	set_kernel_text_ro();
 	return 0;
 }
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index bcd7f00..9ca4c57 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -1155,12 +1155,17 @@ static noinline int do_test_wp_bit(void)
 const int rodata_test_data = 0xC3;
 EXPORT_SYMBOL_GPL(rodata_test_data);
 
+static int kernel_set_to_readonly;
+
 /* used by ftrace */
 void set_kernel_text_rw(void)
 {
 	unsigned long start = PFN_ALIGN(_text);
 	unsigned long size = PFN_ALIGN(_etext) - start;
 
+	if (!kernel_set_to_readonly)
+		return;
+
 	printk(KERN_INFO "Set kernel text: %lx - %lx for read write\n",
 	       start, start+size);
 
@@ -1173,6 +1178,9 @@ void set_kernel_text_ro(void)
 	unsigned long start = PFN_ALIGN(_text);
 	unsigned long size = PFN_ALIGN(_etext) - start;
 
+	if (!kernel_set_to_readonly)
+		return;
+
 	printk(KERN_INFO "Set kernel text: %lx - %lx for read only\n",
 	       start, start+size);
 
@@ -1188,6 +1196,8 @@ void mark_rodata_ro(void)
 	printk(KERN_INFO "Write protecting the kernel text: %luk\n",
 		size >> 10);
 
+	kernel_set_to_readonly = 1;
+
 #ifdef CONFIG_CPA_DEBUG
 	printk(KERN_INFO "Testing CPA: Reverting %lx-%lx\n",
 		start, start+size);
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 8c1b5ee..c204433 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -986,12 +986,17 @@ void free_initmem(void)
 const int rodata_test_data = 0xC3;
 EXPORT_SYMBOL_GPL(rodata_test_data);
 
+static int kernel_set_to_readonly;
+
 /* used by ftrace */
 void set_kernel_text_rw(void)
 {
 	unsigned long start = PFN_ALIGN(_stext);
 	unsigned long end = PFN_ALIGN(__start_rodata);
 
+	if (!kernel_set_to_readonly)
+		return;
+
 	printk(KERN_INFO "Set kernel text: %lx - %lx for read write\n",
 	       start, end);
 
@@ -1004,6 +1009,9 @@ void set_kernel_text_ro(void)
 	unsigned long start = PFN_ALIGN(_stext);
 	unsigned long end = PFN_ALIGN(__start_rodata);
 
+	if (!kernel_set_to_readonly)
+		return;
+
 	printk(KERN_INFO "Set kernel text: %lx - %lx for read only\n",
 	       start, end);
 
@@ -1020,6 +1028,8 @@ void mark_rodata_ro(void)
 	       (end - start) >> 10);
 	set_memory_ro(start, (end - start) >> PAGE_SHIFT);
 
+	kernel_set_to_readonly = 1;
+
 	/*
 	 * The rodata section (but not the kernel text!) should also be
 	 * not-executable.
-- 
1.5.6.5

-- 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/