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
get_current(void)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