Merge branch 'master' of /home/davem/src/GIT/linux-2.6/

1 files changed, 17 insertions, 0 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 5a1b9758fd62..309689245431 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -189,9 +189,26 @@ static void wait_for_nmi(void)
         nmi_wait_count++;
 }
 
+static inline int
+within(unsigned long addr, unsigned long start, unsigned long end)
+{
+        return addr >= start && addr < end;
+}
+
 static int
 do_ftrace_mod_code(unsigned long ip, void *new_code)
 {
+        /*
+         * On x86_64, kernel text mappings are mapped read-only with
+         * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
+         * of the kernel text mapping to modify the kernel text.
+         *
+         * For 32bit kernels, these mappings are same and we can use
+         * kernel identity mapping to modify code.
+         */
+        if (within(ip, (unsigned long)_text, (unsigned long)_etext))
+                ip = (unsigned long)__va(__pa(ip));
+
         mod_code_ip = (void *)ip;
         mod_code_newcode = new_code;