[PATCH v7 1/3] kprobes/ftrace: Use ftrace_location() when [dis]arming probes

[Jisheng Zhang]

Ftrace location could include more than a single instruction in case
of some architectures (powerpc64, for now). In this case, kprobe is
permitted on any of those instructions, and uses ftrace infrastructure
for functioning.

However, [dis]arm_kprobe_ftrace() uses the kprobe address when setting
up ftrace filter IP. This won't work if the address points to any
instruction apart from the one that has a branch to _mcount(). To
resolve this, have [dis]arm_kprobe_ftrace() use ftrace_function() to
identify the filter IP.

Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
 kernel/kprobes.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 53534aa258a6..5c630b424e3a 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -986,9 +986,10 @@ static int prepare_kprobe(struct kprobe *p)
 static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
 			       int *cnt)
 {
+	unsigned long ftrace_ip = ftrace_location((unsigned long)p->addr);
 	int ret = 0;
 
-	ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 0, 0);
+	ret = ftrace_set_filter_ip(ops, ftrace_ip, 0, 0);
 	if (ret) {
 		pr_debug("Failed to arm kprobe-ftrace at %pS (%d)\n",
 			 p->addr, ret);
@@ -1011,7 +1012,7 @@ static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
 	 * At this point, sinec ops is not registered, we should be sefe from
 	 * registering empty filter.
 	 */
-	ftrace_set_filter_ip(ops, (unsigned long)p->addr, 1, 0);
+	ftrace_set_filter_ip(ops, ftrace_ip, 1, 0);
 	return ret;
 }
 
@@ -1028,6 +1029,7 @@ static int arm_kprobe_ftrace(struct kprobe *p)
 static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
 				  int *cnt)
 {
+	unsigned long ftrace_ip = ftrace_location((unsigned long)p->addr);
 	int ret = 0;
 
 	if (*cnt == 1) {
@@ -1038,7 +1040,7 @@ static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
 
 	(*cnt)--;
 
-	ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 1, 0);
+	ret = ftrace_set_filter_ip(ops, ftrace_ip, 1, 0);
 	WARN_ONCE(ret < 0, "Failed to disarm kprobe-ftrace at %pS (%d)\n",
 		  p->addr, ret);
 	return ret;
-- 
2.24.1