GNU Linux-libre 6.7.9-gnu
[releases.git] / 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) && \
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 */