powerpc: Have patch_instruction detect faults

For ftrace to use the patch_instruction code, it needs to check for
faults on write. Ftrace updates code all over the kernel, and we need to
know if code is updated or not due to protections that are placed on
some portions of the kernel. If ftrace does not detect a fault, it will
error later on, and it will be much more difficult to find the problem.

By changing patch_instruction() to detect faults, then ftrace will be
able to make use of it too.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 10 insertions, 4 deletions

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 7c975d43e3f3..dd223b3eb333 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -13,17 +13,23 @@
 #include <linux/mm.h>
 #include <asm/page.h>
 #include <asm/code-patching.h>
+#include <asm/uaccess.h>
 
 
-void patch_instruction(unsigned int *addr, unsigned int instr)
+int patch_instruction(unsigned int *addr, unsigned int instr)
 {
-        *addr = instr;
+        int err;
+
+        err = __put_user(instr, addr);
+        if (err)
+                return err;
         asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" : : "r" (addr));
+        return 0;
 }
 
-void patch_branch(unsigned int *addr, unsigned long target, int flags)
+int patch_branch(unsigned int *addr, unsigned long target, int flags)
 {
-        patch_instruction(addr, create_branch(addr, target, flags));
+        return patch_instruction(addr, create_branch(addr, target, flags));
 }
 
 unsigned int create_branch(const unsigned int *addr,