linux-kernel - [PATCH 3/3] static_call: Fix static_call

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Message-ID: <20210318113610.739542434@infradead.org>
Date:   Thu, 18 Mar 2021 12:31:59 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, jpoimboe@...hat.com, jbaron@...mai.com,
        rostedt@...dmis.org, ardb@...nel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        sumit.garg@...aro.org, oliver.sang@...el.com, jarkko@...nel.org
Subject: [PATCH 3/3] static_call: Fix static_call_update() sanity check

Sites that match init_section_contains() get marked as INIT. For
built-in code init_sections contains both __init and __exit text. OTOH
kernel_text_address() only explicitly includes __init text (and there
are no __exit text markers).

Match what jump_label already does and ignore the warning for INIT
sites. Also see the excellent changelog for commit: 8f35eaa5f2de
("jump_label: Don't warn on __exit jump entries")

Fixes: 9183c3f9ed710 ("static_call: Add inline static call infrastructure")
Reported-by: Sumit Garg <sumit.garg@...aro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/jump_label.c  |    8 ++++++++
 kernel/static_call.c |   11 ++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -407,6 +407,14 @@ static bool jump_label_can_update(struct
 		return false;
 
 	if (!kernel_text_address(jump_entry_code(entry))) {
+		/*
+		 * This skips patching __exit, which is part of
+		 * init_section_contains() but is not part of
+		 * kernel_text_address().
+		 *
+		 * Skipping __exit is fine since it will never
+		 * be executed.
+		 */
 		WARN_ONCE(!jump_entry_is_init(entry),
 			  "can't patch jump_label at %pS",
 			  (void *)jump_entry_code(entry));
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -181,7 +181,16 @@ void __static_call_update(struct static_
 				continue;
 
 			if (!kernel_text_address((unsigned long)site_addr)) {
-				WARN_ONCE(1, "can't patch static call site at %pS",
+				/*
+				 * This skips patching __exit, which is part of
+				 * init_section_contains() but is not part of
+				 * kernel_text_address().
+				 *
+				 * Skipping __exit is fine since it will never
+				 * be executed.
+				 */
+				WARN_ONCE(!static_call_is_init(site),
+					  "can't patch static call site at %pS",
 					  site_addr);
 				continue;
 			}