arch/arm/include/asm/tls.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __ASMARM_TLS_H
   3 #define __ASMARM_TLS_H
   4
   5 #include <linux/compiler.h>
   6 #include <asm/thread_info.h>
   7
   8 #ifdef __ASSEMBLY__
   9 #include <asm/asm-offsets.h>
  10         .macro switch_tls_none, base, tp, tpuser, tmp1, tmp2
  11         .endm
  12
  13         .macro switch_tls_v6k, base, tp, tpuser, tmp1, tmp2
  14         mrc     p15, 0, \tmp2, c13, c0, 2       @ get the user r/w register
  15         mcr     p15, 0, \tp, c13, c0, 3         @ set TLS register
  16         mcr     p15, 0, \tpuser, c13, c0, 2     @ and the user r/w register
  17         str     \tmp2, [\base, #TI_TP_VALUE + 4] @ save it
  18         .endm
  19
  20         .macro switch_tls_v6, base, tp, tpuser, tmp1, tmp2
  21         ldr     \tmp1, =elf_hwcap
  22         ldr     \tmp1, [\tmp1, #0]
  23         mov     \tmp2, #0xffff0fff
  24         tst     \tmp1, #HWCAP_TLS               @ hardware TLS available?
  25         streq   \tp, [\tmp2, #-15]              @ set TLS value at 0xffff0ff0
  26         mrcne   p15, 0, \tmp2, c13, c0, 2       @ get the user r/w register
  27         mcrne   p15, 0, \tp, c13, c0, 3         @ yes, set TLS register
  28         mcrne   p15, 0, \tpuser, c13, c0, 2     @ set user r/w register
  29         strne   \tmp2, [\base, #TI_TP_VALUE + 4] @ save it
  30         .endm
  31
  32         .macro switch_tls_software, base, tp, tpuser, tmp1, tmp2
  33         mov     \tmp1, #0xffff0fff
  34         str     \tp, [\tmp1, #-15]              @ set TLS value at 0xffff0ff0
  35         .endm
  36 #endif
  37
  38 #ifdef CONFIG_TLS_REG_EMUL
  39 #define tls_emu         1
  40 #define has_tls_reg             1
  41 #define switch_tls      switch_tls_none
  42 #elif defined(CONFIG_CPU_V6)
  43 #define tls_emu         0
  44 #define has_tls_reg             (elf_hwcap & HWCAP_TLS)
  45 #define switch_tls      switch_tls_v6
  46 #elif defined(CONFIG_CPU_32v6K)
  47 #define tls_emu         0
  48 #define has_tls_reg             1
  49 #define switch_tls      switch_tls_v6k
  50 #else
  51 #define tls_emu         0
  52 #define has_tls_reg             0
  53 #define switch_tls      switch_tls_software
  54 #endif
  55
  56 #ifndef __ASSEMBLY__
  57
  58 static inline void set_tls(unsigned long val)
  59 {
  60         struct thread_info *thread;
  61
  62         thread = current_thread_info();
  63
  64         thread->tp_value[0] = val;
  65
  66         /*
  67          * This code runs with preemption enabled and therefore must
  68          * be reentrant with respect to switch_tls.
  69          *
  70          * We need to ensure ordering between the shadow state and the
  71          * hardware state, so that we don't corrupt the hardware state
  72          * with a stale shadow state during context switch.
  73          *
  74          * If we're preempted here, switch_tls will load TPIDRURO from
  75          * thread_info upon resuming execution and the following mcr
  76          * is merely redundant.
  77          */
  78         barrier();
  79
  80         if (!tls_emu) {
  81                 if (has_tls_reg) {
  82                         asm("mcr p15, 0, %0, c13, c0, 3"
  83                             : : "r" (val));
  84                 } else {
  85 #ifdef CONFIG_KUSER_HELPERS
  86                         /*
  87                          * User space must never try to access this
  88                          * directly.  Expect your app to break
  89                          * eventually if you do so.  The user helper
  90                          * at 0xffff0fe0 must be used instead.  (see
  91                          * entry-armv.S for details)
  92                          */
  93                         *((unsigned int *)0xffff0ff0) = val;
  94 #endif
  95                 }
  96
  97         }
  98 }
  99
 100 static inline unsigned long get_tpuser(void)
 101 {
 102         unsigned long reg = 0;
 103
 104         if (has_tls_reg && !tls_emu)
 105                 __asm__("mrc p15, 0, %0, c13, c0, 2" : "=r" (reg));
 106
 107         return reg;
 108 }
 109
 110 static inline void set_tpuser(unsigned long val)
 111 {
 112         /* Since TPIDRURW is fully context-switched (unlike TPIDRURO),
 113          * we need not update thread_info.
 114          */
 115         if (has_tls_reg && !tls_emu) {
 116                 asm("mcr p15, 0, %0, c13, c0, 2"
 117                     : : "r" (val));
 118         }
 119 }
 120
 121 static inline void flush_tls(void)
 122 {
 123         set_tls(0);
 124         set_tpuser(0);
 125 }
 126
 127 #endif
 128 #endif  /* __ASMARM_TLS_H */