arch/arm64/include/asm/mte.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * Copyright (C) 2020 ARM Ltd.
   4  */
   5 #ifndef __ASM_MTE_H
   6 #define __ASM_MTE_H
   7
   8 #include <asm/compiler.h>
   9 #include <asm/mte-def.h>
  10
  11 #ifndef __ASSEMBLY__
  12
  13 #include <linux/bitfield.h>
  14 #include <linux/kasan-enabled.h>
  15 #include <linux/page-flags.h>
  16 #include <linux/sched.h>
  17 #include <linux/types.h>
  18
  19 #include <asm/pgtable-types.h>
  20
  21 void mte_clear_page_tags(void *addr);
  22 unsigned long mte_copy_tags_from_user(void *to, const void __user *from,
  23                                       unsigned long n);
  24 unsigned long mte_copy_tags_to_user(void __user *to, void *from,
  25                                     unsigned long n);
  26 int mte_save_tags(struct page *page);
  27 void mte_save_page_tags(const void *page_addr, void *tag_storage);
  28 void mte_restore_tags(swp_entry_t entry, struct page *page);
  29 void mte_restore_page_tags(void *page_addr, const void *tag_storage);
  30 void mte_invalidate_tags(int type, pgoff_t offset);
  31 void mte_invalidate_tags_area(int type);
  32 void *mte_allocate_tag_storage(void);
  33 void mte_free_tag_storage(char *storage);
  34
  35 #ifdef CONFIG_ARM64_MTE
  36
  37 /* track which pages have valid allocation tags */
  38 #define PG_mte_tagged   PG_arch_2
  39 /* simple lock to avoid multiple threads tagging the same page */
  40 #define PG_mte_lock     PG_arch_3
  41
  42 static inline void set_page_mte_tagged(struct page *page)
  43 {
  44         /*
  45          * Ensure that the tags written prior to this function are visible
  46          * before the page flags update.
  47          */
  48         smp_wmb();
  49         set_bit(PG_mte_tagged, &page->flags);
  50 }
  51
  52 static inline bool page_mte_tagged(struct page *page)
  53 {
  54         bool ret = test_bit(PG_mte_tagged, &page->flags);
  55
  56         /*
  57          * If the page is tagged, ensure ordering with a likely subsequent
  58          * read of the tags.
  59          */
  60         if (ret)
  61                 smp_rmb();
  62         return ret;
  63 }
  64
  65 /*
  66  * Lock the page for tagging and return 'true' if the page can be tagged,
  67  * 'false' if already tagged. PG_mte_tagged is never cleared and therefore the
  68  * locking only happens once for page initialisation.
  69  *
  70  * The page MTE lock state:
  71  *
  72  *   Locked:    PG_mte_lock && !PG_mte_tagged
  73  *   Unlocked:  !PG_mte_lock || PG_mte_tagged
  74  *
  75  * Acquire semantics only if the page is tagged (returning 'false').
  76  */
  77 static inline bool try_page_mte_tagging(struct page *page)
  78 {
  79         if (!test_and_set_bit(PG_mte_lock, &page->flags))
  80                 return true;
  81
  82         /*
  83          * The tags are either being initialised or may have been initialised
  84          * already. Check if the PG_mte_tagged flag has been set or wait
  85          * otherwise.
  86          */
  87         smp_cond_load_acquire(&page->flags, VAL & (1UL << PG_mte_tagged));
  88
  89         return false;
  90 }
  91
  92 void mte_zero_clear_page_tags(void *addr);
  93 void mte_sync_tags(pte_t pte, unsigned int nr_pages);
  94 void mte_copy_page_tags(void *kto, const void *kfrom);
  95 void mte_thread_init_user(void);
  96 void mte_thread_switch(struct task_struct *next);
  97 void mte_cpu_setup(void);
  98 void mte_suspend_enter(void);
  99 void mte_suspend_exit(void);
 100 long set_mte_ctrl(struct task_struct *task, unsigned long arg);
 101 long get_mte_ctrl(struct task_struct *task);
 102 int mte_ptrace_copy_tags(struct task_struct *child, long request,
 103                          unsigned long addr, unsigned long data);
 104 size_t mte_probe_user_range(const char __user *uaddr, size_t size);
 105
 106 #else /* CONFIG_ARM64_MTE */
 107
 108 /* unused if !CONFIG_ARM64_MTE, silence the compiler */
 109 #define PG_mte_tagged   0
 110
 111 static inline void set_page_mte_tagged(struct page *page)
 112 {
 113 }
 114 static inline bool page_mte_tagged(struct page *page)
 115 {
 116         return false;
 117 }
 118 static inline bool try_page_mte_tagging(struct page *page)
 119 {
 120         return false;
 121 }
 122 static inline void mte_zero_clear_page_tags(void *addr)
 123 {
 124 }
 125 static inline void mte_sync_tags(pte_t pte, unsigned int nr_pages)
 126 {
 127 }
 128 static inline void mte_copy_page_tags(void *kto, const void *kfrom)
 129 {
 130 }
 131 static inline void mte_thread_init_user(void)
 132 {
 133 }
 134 static inline void mte_thread_switch(struct task_struct *next)
 135 {
 136 }
 137 static inline void mte_suspend_enter(void)
 138 {
 139 }
 140 static inline void mte_suspend_exit(void)
 141 {
 142 }
 143 static inline long set_mte_ctrl(struct task_struct *task, unsigned long arg)
 144 {
 145         return 0;
 146 }
 147 static inline long get_mte_ctrl(struct task_struct *task)
 148 {
 149         return 0;
 150 }
 151 static inline int mte_ptrace_copy_tags(struct task_struct *child,
 152                                        long request, unsigned long addr,
 153                                        unsigned long data)
 154 {
 155         return -EIO;
 156 }
 157
 158 #endif /* CONFIG_ARM64_MTE */
 159
 160 static inline void mte_disable_tco_entry(struct task_struct *task)
 161 {
 162         if (!system_supports_mte())
 163                 return;
 164
 165         /*
 166          * Re-enable tag checking (TCO set on exception entry). This is only
 167          * necessary if MTE is enabled in either the kernel or the userspace
 168          * task in synchronous or asymmetric mode (SCTLR_EL1.TCF0 bit 0 is set
 169          * for both). With MTE disabled in the kernel and disabled or
 170          * asynchronous in userspace, tag check faults (including in uaccesses)
 171          * are not reported, therefore there is no need to re-enable checking.
 172          * This is beneficial on microarchitectures where re-enabling TCO is
 173          * expensive.
 174          */
 175         if (kasan_hw_tags_enabled() ||
 176             (task->thread.sctlr_user & (1UL << SCTLR_EL1_TCF0_SHIFT)))
 177                 asm volatile(SET_PSTATE_TCO(0));
 178 }
 179
 180 #ifdef CONFIG_KASAN_HW_TAGS
 181 void mte_check_tfsr_el1(void);
 182
 183 static inline void mte_check_tfsr_entry(void)
 184 {
 185         if (!kasan_hw_tags_enabled())
 186                 return;
 187
 188         mte_check_tfsr_el1();
 189 }
 190
 191 static inline void mte_check_tfsr_exit(void)
 192 {
 193         if (!kasan_hw_tags_enabled())
 194                 return;
 195
 196         /*
 197          * The asynchronous faults are sync'ed automatically with
 198          * TFSR_EL1 on kernel entry but for exit an explicit dsb()
 199          * is required.
 200          */
 201         dsb(nsh);
 202         isb();
 203
 204         mte_check_tfsr_el1();
 205 }
 206 #else
 207 static inline void mte_check_tfsr_el1(void)
 208 {
 209 }
 210 static inline void mte_check_tfsr_entry(void)
 211 {
 212 }
 213 static inline void mte_check_tfsr_exit(void)
 214 {
 215 }
 216 #endif /* CONFIG_KASAN_HW_TAGS */
 217
 218 #endif /* __ASSEMBLY__ */
 219 #endif /* __ASM_MTE_H  */