diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2021-01-07 14:53:10 +0000 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2021-01-13 12:51:30 +0000 |
| commit | df06824767cc9a32fbdb0e3d3b7e169292a5b5fe (patch) | |
| tree | d7ae3ed43575cd9d66b15112499dd8ca5274f094 /arch | |
| parent | d78050ee35440d7879ed94011c52994b8932e96e (diff) | |
| download | linux-df06824767cc9a32fbdb0e3d3b7e169292a5b5fe.tar.bz2 | |
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
el0_svc_common() leaves lockdep inconsistent with the hardware state,
and is liable to cause issues for any C code or instrumentation
between this and the call to trace_hardirqs_off() which undoes it in
ret_to_user().
This patch removes the redundant tracing calls and associated stale
comments.
Fixes: 23529049c684 ("arm64: entry: fix non-NMI user<->kernel transitions")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210107145310.44616-1-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/kernel/signal.c | 7 | ||||
| -rw-r--r-- | arch/arm64/kernel/syscall.c | 9 |
2 files changed, 1 insertions, 15 deletions
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index f71d6ce4673f..6237486ff6bb 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -914,13 +914,6 @@ static void do_signal(struct pt_regs *regs) asmlinkage void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags) { - /* - * The assembly code enters us with IRQs off, but it hasn't - * informed the tracing code of that for efficiency reasons. - * Update the trace code with the current status. - */ - trace_hardirqs_off(); - do { if (thread_flags & _TIF_NEED_RESCHED) { /* Unmask Debug and SError for the next task */ diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c index f61e9d8cc55a..0bfac95fe464 100644 --- a/arch/arm64/kernel/syscall.c +++ b/arch/arm64/kernel/syscall.c @@ -165,15 +165,8 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) { local_daif_mask(); flags = current_thread_info()->flags; - if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP)) { - /* - * We're off to userspace, where interrupts are - * always enabled after we restore the flags from - * the SPSR. - */ - trace_hardirqs_on(); + if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP)) return; - } local_daif_restore(DAIF_PROCCTX); } |