[v2,6/7] kprobes/ftrace: Use ftrace_location() when [dis]arming probes
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Message ID ecc6ba37ad1a2bf29cd1254083844d51bfaee1bf.1561634177.git.naveen.n.rao@linux.vnet.ibm.com
State New
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Series
  • powerpc/ftrace: Patch out -mprofile-kernel instructions
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snowpatch_ozlabs/apply_patch success Successfully applied on branch next (c7d64b560ce80d8c44f082eee8352f0778a73195)

Commit Message

Naveen N. Rao June 27, 2019, 11:23 a.m. UTC
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.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
 kernel/kprobes.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Patch
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diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 445337c107e0..282ee704e2d8 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -978,10 +978,10 @@  static int prepare_kprobe(struct kprobe *p)
 /* Caller must lock kprobe_mutex */
 static int arm_kprobe_ftrace(struct kprobe *p)
 {
+	unsigned long ftrace_ip = ftrace_location((unsigned long)p->addr);
 	int ret = 0;
 
-	ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,
-				   (unsigned long)p->addr, 0, 0);
+	ret = ftrace_set_filter_ip(&kprobe_ftrace_ops, ftrace_ip, 0, 0);
 	if (ret) {
 		pr_debug("Failed to arm kprobe-ftrace at %pS (%d)\n",
 			 p->addr, ret);
@@ -1005,13 +1005,14 @@  static int arm_kprobe_ftrace(struct kprobe *p)
 	 * non-empty filter_hash for IPMODIFY ops, we're safe from an accidental
 	 * empty filter_hash which would undesirably trace all functions.
 	 */
-	ftrace_set_filter_ip(&kprobe_ftrace_ops, (unsigned long)p->addr, 1, 0);
+	ftrace_set_filter_ip(&kprobe_ftrace_ops, ftrace_ip, 1, 0);
 	return ret;
 }
 
 /* Caller must lock kprobe_mutex */
 static int disarm_kprobe_ftrace(struct kprobe *p)
 {
+	unsigned long ftrace_ip = ftrace_location((unsigned long)p->addr);
 	int ret = 0;
 
 	if (kprobe_ftrace_enabled == 1) {
@@ -1022,8 +1023,7 @@  static int disarm_kprobe_ftrace(struct kprobe *p)
 
 	kprobe_ftrace_enabled--;
 
-	ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,
-			   (unsigned long)p->addr, 1, 0);
+	ret = ftrace_set_filter_ip(&kprobe_ftrace_ops, ftrace_ip, 1, 0);
 	WARN_ONCE(ret < 0, "Failed to disarm kprobe-ftrace at %pS (%d)\n",
 		  p->addr, ret);
 	return ret;