Re: [PATCH v2 12/39] x86/ibt,ftrace: Search for __fentry__ location

[Peter Zijlstra]

On Tue, Mar 01, 2022 at 02:20:16PM -0500, Steven Rostedt wrote:
> On Wed, 02 Mar 2022 00:27:51 +0530
> "Naveen N. Rao" <naveen.n.rao@xxxxxxxxxxxxxxxxxx> wrote:
> 
> > Won't this cause issues with ftrace_set_filter_ip() and others? If the 
> > passed-in ip points to func+0 when the actual ftrace location is at some 
> > offset, the ftrace location check in ftrace_match_addr() will now pass, 
> > resulting in adding func+0 to the hash. Should we also update 
> > ftrace_match_addr() to use the ip returned by ftrace_location()?
> > 
> 
> Yes, ftrace_match_addr() would need to be updated, or at least
> ftrace_set_filter_ip() which is the only user ftrace_match_addr(), and is
> currently only used by kprobes, live kernel patching and the direct
> trampoline example code.

Like so, or is something else needed?

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 68ecd3e35342..d1b30b5c5c23 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4980,7 +4980,8 @@ ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
 {
 	struct ftrace_func_entry *entry;
 
-	if (!ftrace_location(ip))
+	ip = ftrace_location(ip);
+	if (!ip)
 		return -EINVAL;
 
 	if (remove) {