KVM: arm64: pkvm: Implement CONFIG_DEBUG_LIST at EL2

Currently the check functions are stubbed out at EL2. Implement
versions suitable for the constrained EL2 environment.

Signed-off-by: Keir Fraser <keirf@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220131124114.3103337-1-keirf@google.com

arch/arm64/kvm/hyp/nvhe/Makefile

@@ -13,10 +13,11 @@ lib-objs := clear_page.o copy_page.o memcpy.o memset.o
 lib-objs := $(addprefix ../../../lib/, $(lib-objs))
 
 obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
-	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o stub.o page_alloc.o \
+	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o page_alloc.o \
 	 cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o
 obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
 	 ../fpsimd.o ../hyp-entry.o ../exception.o ../pgtable.o
+obj-$(CONFIG_DEBUG_LIST) += list_debug.o
 obj-y += $(lib-objs)
 
 ##

arch/arm64/kvm/hyp/nvhe/list_debug.c

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 - Google LLC
+ * Author: Keir Fraser <keirf@google.com>
+ */
+
+#include <linux/list.h>
+#include <linux/bug.h>
+
+static inline __must_check bool nvhe_check_data_corruption(bool v)
+{
+	return v;
+}
+
+#define NVHE_CHECK_DATA_CORRUPTION(condition)				 \
+	nvhe_check_data_corruption(({					 \
+		bool corruption = unlikely(condition);			 \
+		if (corruption) {					 \
+			if (IS_ENABLED(CONFIG_BUG_ON_DATA_CORRUPTION)) { \
+				BUG_ON(1);				 \
+			} else						 \
+				WARN_ON(1);				 \
+		}							 \
+		corruption;						 \
+	}))
+
+/* The predicates checked here are taken from lib/list_debug.c. */
+
+bool __list_add_valid(struct list_head *new, struct list_head *prev,
+		      struct list_head *next)
+{
+	if (NVHE_CHECK_DATA_CORRUPTION(next->prev != prev) ||
+	    NVHE_CHECK_DATA_CORRUPTION(prev->next != next) ||
+	    NVHE_CHECK_DATA_CORRUPTION(new == prev || new == next))
+		return false;
+
+	return true;
+}
+
+bool __list_del_entry_valid(struct list_head *entry)
+{
+	struct list_head *prev, *next;
+
+	prev = entry->prev;
+	next = entry->next;
+
+	if (NVHE_CHECK_DATA_CORRUPTION(next == LIST_POISON1) ||
+	    NVHE_CHECK_DATA_CORRUPTION(prev == LIST_POISON2) ||
+	    NVHE_CHECK_DATA_CORRUPTION(prev->next != entry) ||
+	    NVHE_CHECK_DATA_CORRUPTION(next->prev != entry))
+		return false;
+
+	return true;
+}

arch/arm64/kvm/hyp/nvhe/stub.c

@@ -1,22 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * Stubs for out-of-line function calls caused by re-using kernel
- * infrastructure at EL2.
- *
- * Copyright (C) 2020 - Google LLC
- */
-
-#include <linux/list.h>
-
-#ifdef CONFIG_DEBUG_LIST
-bool __list_add_valid(struct list_head *new, struct list_head *prev,
-		      struct list_head *next)
-{
-		return true;
-}
-
-bool __list_del_entry_valid(struct list_head *entry)
-{
-		return true;
-}
-#endif