include/asm/current.h

0001 /* SPDX-License-Identifier: GPL-2.0-only */
0002 /*
0003  * Copyright (c) 2021 Keith Packard <keithp@keithp.com>
0004  * Copyright (c) 2021 Google, LLC <ardb@kernel.org>
0005  */
0006
0007 #ifndef _ASM_ARM_CURRENT_H
0008 #define _ASM_ARM_CURRENT_H
0009
0010 #ifndef __ASSEMBLY__
0011 #include <asm/insn.h>
0012
0013 struct task_struct;
0014
0015 extern struct task_struct *__current;
0016
0017 static __always_inline __attribute_const__ struct task_struct *get_current(void)
0018 {
0019     struct task_struct *cur;
0020
0021 #if __has_builtin(__builtin_thread_pointer) && \
0022     defined(CONFIG_CURRENT_POINTER_IN_TPIDRURO) && \
0023     !(defined(CONFIG_THUMB2_KERNEL) && \
0024       defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 130001)
0025     /*
0026      * Use the __builtin helper when available - this results in better
0027      * code, especially when using GCC in combination with the per-task
0028      * stack protector, as the compiler will recognize that it needs to
0029      * load the TLS register only once in every function.
0030      *
0031      * Clang < 13.0.1 gets this wrong for Thumb2 builds:
0032      * https://github.com/ClangBuiltLinux/linux/issues/1485
0033      */
0034     cur = __builtin_thread_pointer();
0035 #elif defined(CONFIG_CURRENT_POINTER_IN_TPIDRURO) || defined(CONFIG_SMP)
0036     asm("0: mrc p15, 0, %0, c13, c0, 3          \n\t"
0037 #ifdef CONFIG_CPU_V6
0038         "1:                         \n\t"
0039         "   .subsection 1                   \n\t"
0040 #if defined(CONFIG_ARM_HAS_GROUP_RELOCS) && \
0041     !(defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
0042         "2: " LOAD_SYM_ARMV6(%0, __current) "       \n\t"
0043         "   b   1b                  \n\t"
0044 #else
0045         "2: ldr %0, 3f                  \n\t"
0046         "   ldr %0, [%0]                \n\t"
0047         "   b   1b                  \n\t"
0048         "3: .long   __current               \n\t"
0049 #endif
0050         "   .previous                   \n\t"
0051         "   .pushsection \".alt.smp.init\", \"a\"       \n\t"
0052         "   .long   0b - .                  \n\t"
0053         "   b   . + (2b - 0b)               \n\t"
0054         "   .popsection                 \n\t"
0055 #endif
0056         : "=r"(cur));
0057 #elif __LINUX_ARM_ARCH__>= 7 || \
0058       !defined(CONFIG_ARM_HAS_GROUP_RELOCS) || \
0059       (defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
0060     cur = __current;
0061 #else
0062     asm(LOAD_SYM_ARMV6(%0, __current) : "=r"(cur));
0063 #endif
0064     return cur;
0065 }
0066
0067 #define current get_current()
0068
0069 #endif /* __ASSEMBLY__ */
0070
0071 #endif /* _ASM_ARM_CURRENT_H */