[PATCH v4 6/6] riscv/ftrace: Add HAVE_FUNCTION_GRAPH_RET_ADDR_PTR support

From: Alan Kao
Date: Tue Feb 13 2018 - 00:42:45 EST


In walk_stackframe, the pc now receives the address from calling
ftrace_graph_ret_addr instead of manual calculation.

Note that the original calculation,
pc = frame->ra - 4
is buggy when the instruction at the return address happened to be a
compressed inst. But since it is not a critical part of ftrace, it is
ignored for now to ease the review process.

Cc: Greentime Hu <greentime@xxxxxxxxxxxxx>
Signed-off-by: Alan Kao <alankao@xxxxxxxxxxxxx>
---
arch/riscv/kernel/ftrace.c | 2 +-
arch/riscv/kernel/stacktrace.c | 6 ++++++
2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index 48b5353691c3..1157b6b52d25 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -151,7 +151,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
return;

err = ftrace_push_return_trace(old, self_addr, &trace.depth,
- frame_pointer, NULL);
+ frame_pointer, parent);
if (err == -EBUSY)
return;
*parent = return_hooker;
diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index 559aae781154..a4b1d94371a0 100644
--- a/arch/riscv/kernel/stacktrace.c
+++ b/arch/riscv/kernel/stacktrace.c
@@ -18,6 +18,7 @@
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/stacktrace.h>
+#include <linux/ftrace.h>

#ifdef CONFIG_FRAME_POINTER

@@ -63,7 +64,12 @@ static void notrace walk_stackframe(struct task_struct *task,
frame = (struct stackframe *)fp - 1;
sp = fp;
fp = frame->fp;
+#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+ pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
+ (unsigned long *)(fp - 8));
+#else
pc = frame->ra - 0x4;
+#endif
}
}

--
2.15.1