Messages in this thread Patch in this message | | | Date | Tue, 30 May 2023 10:46:27 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH] arm64: Fix 'lock held when returning to user space' lockdep warning |
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Hi Eric,
The subject line for this patch is misleading, as it makes it sound like we're currently hitting a warning of the form:
lock held when returning to user space
... when in actuality this patch is *adding* support for that warning.
This is a missing feature, not a fix (and e.g. doesn't require backporting to stable).
On Fri, May 26, 2023 at 06:48:23PM +0000, Eric Chan wrote: > The arm64 architecture lacks support for CONFIG_GENERIC_ENTRY, resulting > in the failure to report the lockdep warning > "lock held when returning to user space" when lockdep is enabled. > > Rename the function to align with exit_to_user_mode_prepare in > kernel/entry/common.c to improve readability.
Considering the point about the commit title, could you please reword this to be clear that we're adding support for a feature, rather than fixing something that's broken, e.g.
| 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.
With that wording:
Acked-by: Mark Rutland <mark.rutland@arm.com>
Thanks, Mark.
> Signed-off-by: Eric Chan <ericchancf@google.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 >
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