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Message-ID: <20220224151322.714815604@infradead.org>
User-Agent: quilt/0.66
Date:   Thu, 24 Feb 2022 15:51:50 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     x86@kernel.org, joao@overdrivepizza.com, hjl.tools@gmail.com,
        jpoimboe@redhat.com, andrew.cooper3@citrix.com
Cc:     linux-kernel@vger.kernel.org, peterz@infradead.org,
        ndesaulniers@google.com, keescook@chromium.org,
        samitolvanen@google.com, mark.rutland@arm.com,
        alyssa.milburn@intel.com, mbenes@suse.cz, rostedt@goodmis.org,
        mhiramat@kernel.org, alexei.starovoitov@gmail.com
Subject: [PATCH v2 12/39] x86/ibt,ftrace: Search for __fentry__ location
References: <20220224145138.952963315@infradead.org>
MIME-Version: 1.0
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Precedence: bulk

Have ftrace_location() search the symbol for the __fentry__ location
when it isn't at func+0 and use this for {,un}register_ftrace_direct().

This avoids a whole bunch of assumptions about __fentry__ being at
func+0.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/trace/ftrace.c |   30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1578,7 +1578,24 @@ unsigned long ftrace_location_range(unsi
  */
 unsigned long ftrace_location(unsigned long ip)
 {
-	return ftrace_location_range(ip, ip);
+	struct dyn_ftrace *rec;
+	unsigned long offset;
+	unsigned long size;
+
+	rec = lookup_rec(ip, ip);
+	if (!rec) {
+		if (!kallsyms_lookup_size_offset(ip, &size, &offset))
+			goto out;
+
+		if (!offset)
+			rec = lookup_rec(ip - offset, (ip - offset) + size);
+	}
+
+	if (rec)
+		return rec->ip;
+
+out:
+	return 0;
 }
 
 /**
@@ -5110,11 +5127,16 @@ int register_ftrace_direct(unsigned long
 	struct ftrace_func_entry *entry;
 	struct ftrace_hash *free_hash = NULL;
 	struct dyn_ftrace *rec;
-	int ret = -EBUSY;
+	int ret = -ENODEV;
 
 	mutex_lock(&direct_mutex);
 
+	ip = ftrace_location(ip);
+	if (!ip)
+		goto out_unlock;
+
 	/* See if there's a direct function at @ip already */
+	ret = -EBUSY;
 	if (ftrace_find_rec_direct(ip))
 		goto out_unlock;
 
@@ -5222,6 +5244,10 @@ int unregister_ftrace_direct(unsigned lo
 
 	mutex_lock(&direct_mutex);
 
+	ip = ftrace_location(ip);
+	if (!ip)
+		goto out_unlock;
+
 	entry = find_direct_entry(&ip, NULL);
 	if (!entry)
 		goto out_unlock;