arch/arm/include/asm/current.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Copyright (c) 2021 Keith Packard <keithp@keithp.com>
   4  * Copyright (c) 2021 Google, LLC <ardb@kernel.org>
   5  */
   6
   7 #ifndef _ASM_ARM_CURRENT_H
   8 #define _ASM_ARM_CURRENT_H
   9
  10 #ifndef __ASSEMBLY__
  11 #include <asm/insn.h>
  12
  13 struct task_struct;
  14
  15 extern struct task_struct *__current;
  16
  17 static __always_inline __attribute_const__ struct task_struct *get_current(void)
  18 {
  19         struct task_struct *cur;
  20
  21 #if __has_builtin(__builtin_thread_pointer) && defined(CONFIG_CURRENT_POINTER_IN_TPIDRURO)
  22         /*
  23          * Use the __builtin helper when available - this results in better
  24          * code, especially when using GCC in combination with the per-task
  25          * stack protector, as the compiler will recognize that it needs to
  26          * load the TLS register only once in every function.
  27          */
  28         cur = __builtin_thread_pointer();
  29 #elif defined(CONFIG_CURRENT_POINTER_IN_TPIDRURO) || defined(CONFIG_SMP)
  30         asm("0: mrc p15, 0, %0, c13, c0, 3                      \n\t"
  31 #ifdef CONFIG_CPU_V6
  32             "1:                                                 \n\t"
  33             "   .subsection 1                                   \n\t"
  34 #if defined(CONFIG_ARM_HAS_GROUP_RELOCS) && \
  35     !(defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
  36             "2: " LOAD_SYM_ARMV6(%0, __current) "               \n\t"
  37             "   b       1b                                      \n\t"
  38 #else
  39             "2: ldr     %0, 3f                                  \n\t"
  40             "   ldr     %0, [%0]                                \n\t"
  41             "   b       1b                                      \n\t"
  42             "3: .long   __current                               \n\t"
  43 #endif
  44             "   .previous                                       \n\t"
  45             "   .pushsection \".alt.smp.init\", \"a\"           \n\t"
  46             "   .long   0b - .                                  \n\t"
  47             "   b       . + (2b - 0b)                           \n\t"
  48             "   .popsection                                     \n\t"
  49 #endif
  50             : "=r"(cur));
  51 #elif __LINUX_ARM_ARCH__>= 7 || \
  52       !defined(CONFIG_ARM_HAS_GROUP_RELOCS) || \
  53       (defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
  54         cur = __current;
  55 #else
  56         asm(LOAD_SYM_ARMV6(%0, __current) : "=r"(cur));
  57 #endif
  58         return cur;
  59 }
  60
  61 #define current get_current()
  62
  63 #endif /* __ASSEMBLY__ */
  64
  65 #endif /* _ASM_ARM_CURRENT_H */