linux-kernel - [PATCH v2] arm64: lockdep: enable checks for held locks when returning to userspace

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Message-ID: <20230531090909.357047-1-ericchancf@google.com>
Date:   Wed, 31 May 2023 09:09:09 +0000
From:   Eric Chan <ericchancf@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     "Paul E . McKenney" <paulmck@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Mukesh Ojha <quic_mojha@...cinc.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Eric Chan <ericchancf@...gle.com>
Subject: [PATCH v2] arm64: lockdep: enable checks for held locks when
 returning to userspace

Currently arm64 doesn't use CONFIG_GENERIC_ENTRY and doesn't call
lockdep_sys_exit() when returning to userspace.
This means that lockdep won't check for held locks when
returning to userspace, which would be useful to detect kernel bugs.

Call lockdep_sys_exit() when returning to userspace,
enabling checking for held locks.

At the same time, rename arm64's prepare_exit_to_user_mode() to
exit_to_user_mode_prepare() to more clearly align with the naming
in the generic entry code.

Signed-off-by: Eric Chan <ericchancf@...gle.com>
Acked-by: Mark Rutland <mark.rutland@....com>
---
 arch/arm64/kernel/entry-common.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 3af3c01c93a6..9d6827201b6c 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -126,7 +126,7 @@ static __always_inline void __exit_to_user_mode(void)
 	lockdep_hardirqs_on(CALLER_ADDR0);
 }
 
-static __always_inline void prepare_exit_to_user_mode(struct pt_regs *regs)
+static __always_inline void exit_to_user_mode_prepare(struct pt_regs *regs)
 {
 	unsigned long flags;
 
@@ -135,11 +135,13 @@ static __always_inline void prepare_exit_to_user_mode(struct pt_regs *regs)
 	flags = read_thread_flags();
 	if (unlikely(flags & _TIF_WORK_MASK))
 		do_notify_resume(regs, flags);
+
+	lockdep_sys_exit();
 }
 
 static __always_inline void exit_to_user_mode(struct pt_regs *regs)
 {
-	prepare_exit_to_user_mode(regs);
+	exit_to_user_mode_prepare(regs);
 	mte_check_tfsr_exit();
 	__exit_to_user_mode();
 }
-- 
2.41.0.rc0.172.g3f132b7071-goog
V1 -> V2 : Revise the commit message to make it clearer and avoid any misleading information.