[PATCH 3.16 36/76] kprobes/x86: Blacklist indirect thunk functions for kprobes

[Ben Hutchings]

3.16.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

commit c1804a236894ecc942da7dc6c5abe209e56cba93 upstream.

Mark __x86_indirect_thunk_* functions as blacklist for kprobes
because those functions can be called from anywhere in the kernel
including blacklist functions of kprobes.

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/151629209111.10241.5444852823378068683.stgit@devbox
[bwh: Backported to 3.16: exports are still done from C]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -24,7 +24,9 @@ ENDPROC(__x86_indirect_thunk_\reg)
  * than one per register with the correct names. So we do it
  * the simple and nasty way...
  */
-#define GENERATE_THUNK(reg) THUNK reg
+#define __EXPORT_THUNK(sym) _ASM_NOKPROBE(sym)
+#define EXPORT_THUNK(reg) __EXPORT_THUNK(__x86_indirect_thunk_ ## reg)
+#define GENERATE_THUNK(reg) THUNK reg ; EXPORT_THUNK(reg)
 
 GENERATE_THUNK(_ASM_AX)
 GENERATE_THUNK(_ASM_BX)