arm64: entry: remove redundant IRQ flag tracing
All EL0 returns go via ret_to_user(), which masks IRQs and notifies
lockdep and tracing before calling into do_notify_resume(). Therefore,
there's no need for do_notify_resume() to call trace_hardirqs_off(), and
the comment is stale. The call is simply redundant.
In ret_to_user() we call exit_to_user_mode(), which notifies lockdep and
tracing the IRQs will be enabled in userspace, so there's no need for
el0_svc_common() to call trace_hardirqs_on() before returning. Further,
at the start of ret_to_user() we call trace_hardirqs_off(), so not only
is this redundant, but it is immediately undone.
In addition to being redundant, the trace_hardirqs_on() in
trace_hardirqs_on() isn't consistent with the HW state, and is liable to
cause issues for any C code or instrumentation invoked before this is
undone in ret_to_user(). While we appear to get away with this in
practice, it's very fragile and liable to break if we make changes in
this area.
This patch removes the redundant tracing calls and associated stale
comments.
Fixes: 23529049c6842382 ("arm64: entry: fix non-NMI user<->kernel transitions")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
2 files changed
