Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fixes from Catalin Marinas:

 - Update the compat layer to allow single-byte watchpoints on all
   addresses (similar to the native support)

 - arm_pmu: fix the restoration of the counters on the
   CPU_PM_ENTER_FAILED path

 - Fix build regression with vDSO and Makefile not stripping
   CROSS_COMPILE_COMPAT

 - Fix the CTR_EL0 (cache type register) sanitisation on heterogeneous
   machines (e.g. big.LITTLE)

 - Fix the interrupt controller priority mask value when pseudo-NMIs are
   enabled

 - arm64 kprobes fixes: recovering of the PSTATE.D flag in the
   single-step exception handler, NOKPROBE annotations for
   unwind_frame() and walk_stackframe(), remove unneeded
   rcu_read_lock/unlock from debug handlers

 - Several gcc fall-through warnings

 - Unused variable warnings

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: Make debug exception handlers visible from RCU
  arm64: kprobes: Recover pstate.D in single-step exception handler
  arm64/mm: fix variable 'tag' set but not used
  arm64/mm: fix variable 'pud' set but not used
  arm64: Remove unneeded rcu_read_lock from debug handlers
  arm64: unwind: Prohibit probing on return_address()
  arm64: Lower priority mask for GIC_PRIO_IRQON
  arm64/efi: fix variable 'si' set but not used
  arm64: cpufeature: Fix feature comparison for CTR_EL0.{CWG,ERG}
  arm64: vdso: Fix Makefile regression
  arm64: module: Mark expected switch fall-through
  arm64: smp: Mark expected switch fall-through
  arm64: hw_breakpoint: Fix warnings about implicit fallthrough
  drivers/perf: arm_pmu: Fix failure path in PM notifier
  arm64: compat: Allow single-byte watchpoints on all addresses

1 files changed, 49 insertions, 8 deletions

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 9568c116ac7f..cfd65b63f36f 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -777,6 +777,53 @@ void __init hook_debug_fault_code(int nr,
 	debug_fault_info[nr].name	= name;
 }
 
+/*
+ * In debug exception context, we explicitly disable preemption despite
+ * having interrupts disabled.
+ * This serves two purposes: it makes it much less likely that we would
+ * accidentally schedule in exception context and it will force a warning
+ * if we somehow manage to schedule by accident.
+ */
+static void debug_exception_enter(struct pt_regs *regs)
+{
+	/*
+	 * Tell lockdep we disabled irqs in entry.S. Do nothing if they were
+	 * already disabled to preserve the last enabled/disabled addresses.
+	 */
+	if (interrupts_enabled(regs))
+		trace_hardirqs_off();
+
+	if (user_mode(regs)) {
+		RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
+	} else {
+		/*
+		 * We might have interrupted pretty much anything.  In
+		 * fact, if we're a debug exception, we can even interrupt
+		 * NMI processing. We don't want this code makes in_nmi()
+		 * to return true, but we need to notify RCU.
+		 */
+		rcu_nmi_enter();
+	}
+
+	preempt_disable();
+
+	/* This code is a bit fragile.  Test it. */
+	RCU_LOCKDEP_WARN(!rcu_is_watching(), "exception_enter didn't work");
+}
+NOKPROBE_SYMBOL(debug_exception_enter);
+
+static void debug_exception_exit(struct pt_regs *regs)
+{
+	preempt_enable_no_resched();
+
+	if (!user_mode(regs))
+		rcu_nmi_exit();
+
+	if (interrupts_enabled(regs))
+		trace_hardirqs_on();
+}
+NOKPROBE_SYMBOL(debug_exception_exit);
+
 #ifdef CONFIG_ARM64_ERRATUM_1463225
 DECLARE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa);
 
@@ -817,12 +864,7 @@ asmlinkage void __exception do_debug_exception(unsigned long addr_if_watchpoint,
 	if (cortex_a76_erratum_1463225_debug_handler(regs))
 		return;
 
-	/*
-	 * Tell lockdep we disabled irqs in entry.S. Do nothing if they were
-	 * already disabled to preserve the last enabled/disabled addresses.
-	 */
-	if (interrupts_enabled(regs))
-		trace_hardirqs_off();
+	debug_exception_enter(regs);
 
 	if (user_mode(regs) && !is_ttbr0_addr(pc))
 		arm64_apply_bp_hardening();
@@ -832,7 +874,6 @@ asmlinkage void __exception do_debug_exception(unsigned long addr_if_watchpoint,
 				 inf->sig, inf->code, (void __user *)pc, esr);
 	}
 
-	if (interrupts_enabled(regs))
-		trace_hardirqs_on();
+	debug_exception_exit(regs);
 }
 NOKPROBE_SYMBOL(do_debug_exception);