Re: [PATCH v4 00/45] x86: Kernel IBT

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

On Thu, Mar 10, 2022 at 10:35:32AM +0100, Peter Zijlstra wrote:

> > $ test_progs -t fentry
> > test_fentry_fexit:PASS:fentry_skel_load 0 nsec
> > test_fentry_fexit:PASS:fexit_skel_load 0 nsec
> > test_fentry_fexit:PASS:fentry_attach 0 nsec
> > test_fentry_fexit:FAIL:fexit_attach unexpected error: -1 (errno 19)
> > #54 fentry_fexit:FAIL

This seems to cure the above. fexit_bpf2bpf is still failing, I'll dig
into that after lunch.

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index acb50fb7ed2d..2d86d3c09d64 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5354,6 +5381,11 @@ int modify_ftrace_direct(unsigned long ip,
 	mutex_lock(&direct_mutex);
 
 	mutex_lock(&ftrace_lock);
+
+	ip = ftrace_location(ip);
+	if (!ip)
+		goto out_unlock;
+
 	entry = find_direct_entry(&ip, &rec);
 	if (!entry)
 		goto out_unlock;