linux-kernel - [tip: locking/urgent] static_call: Fix static_call

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Message-ID: <161615670760.398.14295497710199743924.tip-bot2@tip-bot2>
Date:   Fri, 19 Mar 2021 12:25:07 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Sumit Garg <sumit.garg@...aro.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Jarkko Sakkinen <jarkko@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: locking/urgent] static_call: Fix static_call_update() sanity check

The following commit has been merged into the locking/urgent branch of tip:

Commit-ID:     38c93587375053c5b9ef093f4a5ea754538cba32
Gitweb:        https://git.kernel.org/tip/38c93587375053c5b9ef093f4a5ea754538cba32
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Thu, 18 Mar 2021 11:31:51 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Fri, 19 Mar 2021 13:16:44 +01:00

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>
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
---
 kernel/jump_label.c  |  8 ++++++++
 kernel/static_call.c | 11 ++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index c6a39d6..ba39fbb 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -407,6 +407,14 @@ static bool jump_label_can_update(struct jump_entry *entry, bool init)
 		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));
diff --git a/kernel/static_call.c b/kernel/static_call.c
index fc22590..2c5950b 100644
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -181,7 +181,16 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
 				continue;
 
 			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;
 			}