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 */
66
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