[PATCH 6.6 063/175] ftrace: Update the mcount_loc check of skipped entries

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Steven Rostedt <rostedt@goodmis.org>

[ Upstream commit 4a3efc6baff931da9a85c6d2e42c87bd9a827399 ]

Now that weak functions turn into skipped entries, update the check to
make sure the amount that was allocated would fit both the entries that
were allocated as well as those that were skipped.

Cc: bpf <bpf@vger.kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Zheng Yejian <zhengyejian1@huawei.com>
Cc: Martin  Kelly <martin.kelly@crowdstrike.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Link: https://lore.kernel.org/20250218200023.055162048@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@crowdstrike.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 kernel/trace/ftrace.c |   23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6632,7 +6632,28 @@ static int ftrace_process_locs(struct mo
 
 	/* We should have used all pages unless we skipped some */
 	if (pg_unuse) {
-		WARN_ON(!skipped);
+		unsigned long pg_remaining, remaining = 0;
+		unsigned long skip;
+
+		/* Count the number of entries unused and compare it to skipped. */
+		pg_remaining = (ENTRIES_PER_PAGE << pg->order) - pg->index;
+
+		if (!WARN(skipped < pg_remaining, "Extra allocated pages for ftrace")) {
+
+			skip = skipped - pg_remaining;
+
+			for (pg = pg_unuse; pg; pg = pg->next)
+				remaining += 1 << pg->order;
+
+			skip = DIV_ROUND_UP(skip, ENTRIES_PER_PAGE);
+
+			/*
+			 * Check to see if the number of pages remaining would
+			 * just fit the number of entries skipped.
+			 */
+			WARN(skip != remaining, "Extra allocated pages for ftrace: %lu with %lu skipped",
+			     remaining, skipped);
+		}
 		/* Need to synchronize with ftrace_location_range() */
 		synchronize_rcu();
 		ftrace_free_pages(pg_unuse);