linux-kernel - [PATCH 5.11 116/120] static_call: Fix static_call

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Date:   Mon, 22 Mar 2021 13:28:19 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sumit Garg <sumit.garg@...aro.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Jarkko Sakkinen <jarkko@...nel.org>
Subject: [PATCH 5.11 116/120] static_call: Fix static_call_update() sanity check

From: Peter Zijlstra <peterz@...radead.org>

commit 38c93587375053c5b9ef093f4a5ea754538cba32 upstream.

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>
Acked-by: Jarkko Sakkinen <jarkko@...nel.org>
Tested-by: Sumit Garg <sumit.garg@...aro.org>
Link: https://lkml.kernel.org/r/20210318113610.739542434@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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 built-in __exit, which
+		 * is part of init_section_contains() but is
+		 * not part of kernel_text_address().
+		 *
+		 * Skipping built-in __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
@@ -182,7 +182,16 @@ void __static_call_update(struct static_
 			}
 
 			if (!kernel_text_address((unsigned long)site_addr)) {
-				WARN_ONCE(1, "can't patch static call site at %pS",
+				/*
+				 * This skips patching built-in __exit, which
+				 * is part of init_section_contains() but is
+				 * not part of kernel_text_address().
+				 *
+				 * Skipping built-in __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;
 			}