1 files changed, 219 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h
new file mode 100644
index 0000000000..4cedbaa16f
--- /dev/null
+++ b/arch/arm64/include/asm/mte.h
@@ -0,0 +1,219 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 ARM Ltd.
+ */
+#ifndef __ASM_MTE_H
+#define __ASM_MTE_H
+
+#include <asm/compiler.h>
+#include <asm/mte-def.h>
+
+#ifndef __ASSEMBLY__
+
+#include <linux/bitfield.h>
+#include <linux/kasan-enabled.h>
+#include <linux/page-flags.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+
+#include <asm/pgtable-types.h>
+
+void mte_clear_page_tags(void *addr);
+unsigned long mte_copy_tags_from_user(void *to, const void __user *from,
+				      unsigned long n);
+unsigned long mte_copy_tags_to_user(void __user *to, void *from,
+				    unsigned long n);
+int mte_save_tags(struct page *page);
+void mte_save_page_tags(const void *page_addr, void *tag_storage);
+void mte_restore_tags(swp_entry_t entry, struct page *page);
+void mte_restore_page_tags(void *page_addr, const void *tag_storage);
+void mte_invalidate_tags(int type, pgoff_t offset);
+void mte_invalidate_tags_area(int type);
+void *mte_allocate_tag_storage(void);
+void mte_free_tag_storage(char *storage);
+
+#ifdef CONFIG_ARM64_MTE
+
+/* track which pages have valid allocation tags */
+#define PG_mte_tagged	PG_arch_2
+/* simple lock to avoid multiple threads tagging the same page */
+#define PG_mte_lock	PG_arch_3
+
+static inline void set_page_mte_tagged(struct page *page)
+{
+	/*
+	 * Ensure that the tags written prior to this function are visible
+	 * before the page flags update.
+	 */
+	smp_wmb();
+	set_bit(PG_mte_tagged, &page->flags);
+}
+
+static inline bool page_mte_tagged(struct page *page)
+{
+	bool ret = test_bit(PG_mte_tagged, &page->flags);
+
+	/*
+	 * If the page is tagged, ensure ordering with a likely subsequent
+	 * read of the tags.
+	 */
+	if (ret)
+		smp_rmb();
+	return ret;
+}
+
+/*
+ * Lock the page for tagging and return 'true' if the page can be tagged,
+ * 'false' if already tagged. PG_mte_tagged is never cleared and therefore the
+ * locking only happens once for page initialisation.
+ *
+ * The page MTE lock state:
+ *
+ *   Locked:	PG_mte_lock && !PG_mte_tagged
+ *   Unlocked:	!PG_mte_lock || PG_mte_tagged
+ *
+ * Acquire semantics only if the page is tagged (returning 'false').
+ */
+static inline bool try_page_mte_tagging(struct page *page)
+{
+	if (!test_and_set_bit(PG_mte_lock, &page->flags))
+		return true;
+
+	/*
+	 * The tags are either being initialised or may have been initialised
+	 * already. Check if the PG_mte_tagged flag has been set or wait
+	 * otherwise.
+	 */
+	smp_cond_load_acquire(&page->flags, VAL & (1UL << PG_mte_tagged));
+
+	return false;
+}
+
+void mte_zero_clear_page_tags(void *addr);
+void mte_sync_tags(pte_t pte);
+void mte_copy_page_tags(void *kto, const void *kfrom);
+void mte_thread_init_user(void);
+void mte_thread_switch(struct task_struct *next);
+void mte_cpu_setup(void);
+void mte_suspend_enter(void);
+void mte_suspend_exit(void);
+long set_mte_ctrl(struct task_struct *task, unsigned long arg);
+long get_mte_ctrl(struct task_struct *task);
+int mte_ptrace_copy_tags(struct task_struct *child, long request,
+			 unsigned long addr, unsigned long data);
+size_t mte_probe_user_range(const char __user *uaddr, size_t size);
+
+#else /* CONFIG_ARM64_MTE */
+
+/* unused if !CONFIG_ARM64_MTE, silence the compiler */
+#define PG_mte_tagged	0
+
+static inline void set_page_mte_tagged(struct page *page)
+{
+}
+static inline bool page_mte_tagged(struct page *page)
+{
+	return false;
+}
+static inline bool try_page_mte_tagging(struct page *page)
+{
+	return false;
+}
+static inline void mte_zero_clear_page_tags(void *addr)
+{
+}
+static inline void mte_sync_tags(pte_t pte)
+{
+}
+static inline void mte_copy_page_tags(void *kto, const void *kfrom)
+{
+}
+static inline void mte_thread_init_user(void)
+{
+}
+static inline void mte_thread_switch(struct task_struct *next)
+{
+}
+static inline void mte_suspend_enter(void)
+{
+}
+static inline void mte_suspend_exit(void)
+{
+}
+static inline long set_mte_ctrl(struct task_struct *task, unsigned long arg)
+{
+	return 0;
+}
+static inline long get_mte_ctrl(struct task_struct *task)
+{
+	return 0;
+}
+static inline int mte_ptrace_copy_tags(struct task_struct *child,
+				       long request, unsigned long addr,
+				       unsigned long data)
+{
+	return -EIO;
+}
+
+#endif /* CONFIG_ARM64_MTE */
+
+static inline void mte_disable_tco_entry(struct task_struct *task)
+{
+	if (!system_supports_mte())
+		return;
+
+	/*
+	 * Re-enable tag checking (TCO set on exception entry). This is only
+	 * necessary if MTE is enabled in either the kernel or the userspace
+	 * task in synchronous or asymmetric mode (SCTLR_EL1.TCF0 bit 0 is set
+	 * for both). With MTE disabled in the kernel and disabled or
+	 * asynchronous in userspace, tag check faults (including in uaccesses)
+	 * are not reported, therefore there is no need to re-enable checking.
+	 * This is beneficial on microarchitectures where re-enabling TCO is
+	 * expensive.
+	 */
+	if (kasan_hw_tags_enabled() ||
+	    (task->thread.sctlr_user & (1UL << SCTLR_EL1_TCF0_SHIFT)))
+		asm volatile(SET_PSTATE_TCO(0));
+}
+
+#ifdef CONFIG_KASAN_HW_TAGS
+void mte_check_tfsr_el1(void);
+
+static inline void mte_check_tfsr_entry(void)
+{
+	if (!system_supports_mte())
+		return;
+
+	mte_check_tfsr_el1();
+}
+
+static inline void mte_check_tfsr_exit(void)
+{
+	if (!system_supports_mte())
+		return;
+
+	/*
+	 * The asynchronous faults are sync'ed automatically with
+	 * TFSR_EL1 on kernel entry but for exit an explicit dsb()
+	 * is required.
+	 */
+	dsb(nsh);
+	isb();
+
+	mte_check_tfsr_el1();
+}
+#else
+static inline void mte_check_tfsr_el1(void)
+{
+}
+static inline void mte_check_tfsr_entry(void)
+{
+}
+static inline void mte_check_tfsr_exit(void)
+{
+}
+#endif /* CONFIG_KASAN_HW_TAGS */
+
+#endif /* __ASSEMBLY__ */
+#endif /* __ASM_MTE_H  */