The MCOUNT_INSN_SIZE is meant to be used to denote the overall
size of the mcount() call. Since a jal instruction is used to
call mcount() the delay slot should be taken into consideration
as well.
This also replaces the MCOUNT_INSN_SIZE usage with the real size
of a single MIPS instruction since, as described above, the
MCOUNT_INSN_SIZE is used to denote the total overhead of the
mcount() call.
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Markos Chandras <markos.chandras@xxxxxxxxxx>
---
arch/mips/include/asm/ftrace.h | 2 +-
arch/mips/kernel/ftrace.c | 4 +++-
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
index 992aaba603b5..70d4a35fb560 100644
--- a/arch/mips/include/asm/ftrace.h
+++ b/arch/mips/include/asm/ftrace.h
@@ -13,7 +13,7 @@
#ifdef CONFIG_FUNCTION_TRACER
#define MCOUNT_ADDR ((unsigned long)(_mcount))
-#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */
+#define MCOUNT_INSN_SIZE 8 /* sizeof mcount call + delay slot */
#ifndef __ASSEMBLY__
extern void _mcount(void);
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 937c54bc8ccc..211460d4617d 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -28,6 +28,8 @@
#define MCOUNT_OFFSET_INSNS 4
#endif
+#define FTRACE_MIPS_INSN_SIZE 4 /* Size of single MIPS instruction */
+
#ifdef CONFIG_DYNAMIC_FTRACE
/* Arch override because MIPS doesn't need to run this from stop_machine() */
@@ -395,7 +397,7 @@ void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
*/
insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
- trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);
+ trace.func = self_ra - (FTRACE_MIPS_INSN_SIZE * insns);
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
--
2.1.0
