[for-next][PATCH 8/9] ftrace: Let ftrace_call_adjust() reject a patch site

[Steven Rostedt <rostedt@kernel.org>]

From: "Jose Fernandez (Anthropic)" <jose.fernandez@linux.dev>

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.

Link: https://patch.msgid.link/20260924-b4-arm64-callops-kcfi-v2-2-587865b6d991@linux.dev
Reviewed-by: Ben Cressey <ben@cressey.dev>
Reviewed-by: Florent Revest (Anthropic) <florent.revest@linux.dev>
Assisted-by: LLM
Signed-off-by: Jose Fernandez (Anthropic) <jose.fernandez@linux.dev>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c8f8dd1cb92f..b2597eb9581b 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -7707,6 +7707,11 @@ static int ftrace_process_locs(struct module *mod,
 		}
 
 		addr = ftrace_call_adjust(addr);
+		/* The architecture may return 0 to reject a patch site */
+		if (!addr) {
+			skipped++;
+			continue;
+		}
 
 		end_offset = (pg->index+1) * sizeof(pg->records[0]);
 		if (end_offset > PAGE_SIZE << pg->order) {
-- 
2.53.0