From c012268b37db6b10b59dac9b7f45956cb9a8bcb2 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Fri, 5 Aug 2016 14:25:53 -0700 Subject: lkdtm: Mark lkdtm_rodata_do_nothing() notrace lkdtm_rodata_do_nothing() is an empty function which is generated in order to test the non-executability of rodata. Currently if function tracing is enabled then an mcount callsite will be generated for lkdtm_rodata_do_nothing(), and it will appear in the list of available functions for function tracing (available_filter_functions). Given it's purpose purely as a test function, it seems preferable for lkdtm_rodata_do_nothing() to be marked notrace, so it doesn't appear as traceable. This also avoids triggering a linker bug on powerpc: https://sourceware.org/bugzilla/show_bug.cgi?id=20428 When the linker sees code that needs to generate a call stub, eg. a branch to mcount(), it assumes the section is executable and dereferences a NULL pointer leading to a linker segfault. Marking lkdtm_rodata_do_nothing() notrace avoids triggering the bug because the function contains no other function calls. Signed-off-by: Michael Ellerman Signed-off-by: Kees Cook Signed-off-by: Greg Kroah-Hartman diff --git a/drivers/misc/lkdtm_rodata.c b/drivers/misc/lkdtm_rodata.c index 166b1db..3564477 100644 --- a/drivers/misc/lkdtm_rodata.c +++ b/drivers/misc/lkdtm_rodata.c @@ -4,7 +4,7 @@ */ #include "lkdtm.h" -void lkdtm_rodata_do_nothing(void) +void notrace lkdtm_rodata_do_nothing(void) { /* Does nothing. We just want an architecture agnostic "return". */ } -- cgit v0.10.2