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) && \ 22 defined(CONFIG_CURRENT_POINTER_IN_TPIDRURO) && \ 23 !(defined(CONFIG_THUMB2_KERNEL) && \ 24 defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 130001) 25 /* 26 * Use the __builtin helper when available - this results in better 27 * code, especially when using GCC in combination with the per-task 28 * stack protector, as the compiler will recognize that it needs to 29 * load the TLS register only once in every function. 30 * 31 * Clang < 13.0.1 gets this wrong for Thumb2 builds: 32 * https://github.com/ClangBuiltLinux/linux/issues/1485 33 */ 34 cur = __builtin_thread_pointer(); 35 #elif defined(CONFIG_CURRENT_POINTER_IN_TPIDRURO) || defined(CONFIG_SMP) 36 asm("0: mrc p15, 0, %0, c13, c0, 3 \n\t" 37 #ifdef CONFIG_CPU_V6 38 "1: \n\t" 39 " .subsection 1 \n\t" 40 #if defined(CONFIG_ARM_HAS_GROUP_RELOCS) && \ 41 !(defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS)) 42 "2: " LOAD_SYM_ARMV6(%0, __current) " \n\t" 43 " b 1b \n\t" 44 #else 45 "2: ldr %0, 3f \n\t" 46 " ldr %0, [%0] \n\t" 47 " b 1b \n\t" 48 "3: .long __current \n\t" 49 #endif 50 " .previous \n\t" 51 " .pushsection \".alt.smp.init\", \"a\" \n\t" 52 " .long 0b - . \n\t" 53 " b . + (2b - 0b) \n\t" 54 " .popsection \n\t" 55 #endif 56 : "=r"(cur)); 57 #elif __LINUX_ARM_ARCH__>= 7 || \ 58 !defined(CONFIG_ARM_HAS_GROUP_RELOCS) || \ 59 (defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS)) 60 cur = __current; 61 #else 62 asm(LOAD_SYM_ARMV6(%0, __current) : "=r"(cur)); 63 #endif 64 return cur; 65 } 66 67 #define current get_current() 68 69 #endif /* __ASSEMBLY__ */ 70 71 #endif /* _ASM_ARM_CURRENT_H */ 72