arch/arm64/include/asm/pointer_auth.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __ASM_POINTER_AUTH_H
   3 #define __ASM_POINTER_AUTH_H
   4
   5 #include <linux/bitops.h>
   6 #include <linux/random.h>
   7
   8 #include <asm/cpufeature.h>
   9 #include <asm/memory.h>
  10 #include <asm/sysreg.h>
  11
  12 #ifdef CONFIG_ARM64_PTR_AUTH
  13 /*
  14  * Each key is a 128-bit quantity which is split across a pair of 64-bit
  15  * registers (Lo and Hi).
  16  */
  17 struct ptrauth_key {
  18         unsigned long lo, hi;
  19 };
  20
  21 /*
  22  * We give each process its own keys, which are shared by all threads. The keys
  23  * are inherited upon fork(), and reinitialised upon exec*().
  24  */
  25 struct ptrauth_keys {
  26         struct ptrauth_key apia;
  27         struct ptrauth_key apib;
  28         struct ptrauth_key apda;
  29         struct ptrauth_key apdb;
  30         struct ptrauth_key apga;
  31 };
  32
  33 static inline void ptrauth_keys_init(struct ptrauth_keys *keys)
  34 {
  35         if (system_supports_address_auth()) {
  36                 get_random_bytes(&keys->apia, sizeof(keys->apia));
  37                 get_random_bytes(&keys->apib, sizeof(keys->apib));
  38                 get_random_bytes(&keys->apda, sizeof(keys->apda));
  39                 get_random_bytes(&keys->apdb, sizeof(keys->apdb));
  40         }
  41
  42         if (system_supports_generic_auth())
  43                 get_random_bytes(&keys->apga, sizeof(keys->apga));
  44 }
  45
  46 #define __ptrauth_key_install(k, v)                             \
  47 do {                                                            \
  48         struct ptrauth_key __pki_v = (v);                       \
  49         write_sysreg_s(__pki_v.lo, SYS_ ## k ## KEYLO_EL1);     \
  50         write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1);     \
  51 } while (0)
  52
  53 static inline void ptrauth_keys_switch(struct ptrauth_keys *keys)
  54 {
  55         if (system_supports_address_auth()) {
  56                 __ptrauth_key_install(APIA, keys->apia);
  57                 __ptrauth_key_install(APIB, keys->apib);
  58                 __ptrauth_key_install(APDA, keys->apda);
  59                 __ptrauth_key_install(APDB, keys->apdb);
  60         }
  61
  62         if (system_supports_generic_auth())
  63                 __ptrauth_key_install(APGA, keys->apga);
  64 }
  65
  66 extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
  67
  68 /*
  69  * The EL0 pointer bits used by a pointer authentication code.
  70  * This is dependent on TBI0 being enabled, or bits 63:56 would also apply.
  71  */
  72 #define ptrauth_user_pac_mask() GENMASK(54, vabits_actual)
  73
  74 /* Only valid for EL0 TTBR0 instruction pointers */
  75 static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
  76 {
  77         return ptr & ~ptrauth_user_pac_mask();
  78 }
  79
  80 #define ptrauth_thread_init_user(tsk)                                   \
  81 do {                                                                    \
  82         struct task_struct *__ptiu_tsk = (tsk);                         \
  83         ptrauth_keys_init(&__ptiu_tsk->thread.keys_user);               \
  84         ptrauth_keys_switch(&__ptiu_tsk->thread.keys_user);             \
  85 } while (0)
  86
  87 #define ptrauth_thread_switch(tsk)      \
  88         ptrauth_keys_switch(&(tsk)->thread.keys_user)
  89
  90 #else /* CONFIG_ARM64_PTR_AUTH */
  91 #define ptrauth_prctl_reset_keys(tsk, arg)      (-EINVAL)
  92 #define ptrauth_strip_insn_pac(lr)      (lr)
  93 #define ptrauth_thread_init_user(tsk)
  94 #define ptrauth_thread_switch(tsk)
  95 #endif /* CONFIG_ARM64_PTR_AUTH */
  96
  97 #endif /* __ASM_POINTER_AUTH_H */