[PATCH RFC 1/8] ftrace: Let ftrace_call_adjust() reject a patch site

[Jose Fernandez (Anthropic)]

When ftrace_call_adjust() returns 0 for a patch site,
ftrace_process_locs() does not skip the site. The NULL test runs before
the adjustment since commit 6eeca746fa5f ("ftrace: Test mcount_loc
addr before calling ftrace_call_addr()"), so the 0 is stored as the
record's ip and ftrace_init_nop() later hits the BUG_ON() in arm64's
patch_map(). Test the adjusted address too and count the site as
skipped.

Reviewed-by: Ben Cressey <ben@xxxxxxxxxxx>
Reviewed-by: Florent Revest (Anthropic) <florent.revest@xxxxxxxxx>
Assisted-by: LLM
Signed-off-by: Jose Fernandez (Anthropic) <jose.fernandez@xxxxxxxxx>
---
 kernel/trace/ftrace.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f9d80c7bd9f16..394f82230e0c3 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -7676,6 +7676,10 @@ static int ftrace_process_locs(struct module *mod,
 		}
 
 		addr = ftrace_call_adjust(addr);
+		if (!addr) {
+			skipped++;
+			continue;
+		}
 
 		end_offset = (pg->index+1) * sizeof(pg->records[0]);
 		if (end_offset > PAGE_SIZE << pg->order) {

-- 
2.52.0