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

From: Eric Chan
Date: Wed May 31 2023 - 05:10:56 EST

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@xxxxxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
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)

-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);
V1 -> V2 : Revise the commit message to make it clearer and avoid any misleading information.