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-rw-r--r--arch/arm/include/asm/current.h71
1 files changed, 71 insertions, 0 deletions
diff --git a/arch/arm/include/asm/current.h b/arch/arm/include/asm/current.h
new file mode 100644
index 000000000..1e1178bf1
--- /dev/null
+++ b/arch/arm/include/asm/current.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2021 Keith Packard <keithp@keithp.com>
+ * Copyright (c) 2021 Google, LLC <ardb@kernel.org>
+ */
+
+#ifndef _ASM_ARM_CURRENT_H
+#define _ASM_ARM_CURRENT_H
+
+#ifndef __ASSEMBLY__
+#include <asm/insn.h>
+
+struct task_struct;
+
+extern struct task_struct *__current;
+
+static __always_inline __attribute_const__ struct task_struct *get_current(void)
+{
+ struct task_struct *cur;
+
+#if __has_builtin(__builtin_thread_pointer) && \
+ defined(CONFIG_CURRENT_POINTER_IN_TPIDRURO) && \
+ !(defined(CONFIG_THUMB2_KERNEL) && \
+ defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 130001)
+ /*
+ * Use the __builtin helper when available - this results in better
+ * code, especially when using GCC in combination with the per-task
+ * stack protector, as the compiler will recognize that it needs to
+ * load the TLS register only once in every function.
+ *
+ * Clang < 13.0.1 gets this wrong for Thumb2 builds:
+ * https://github.com/ClangBuiltLinux/linux/issues/1485
+ */
+ cur = __builtin_thread_pointer();
+#elif defined(CONFIG_CURRENT_POINTER_IN_TPIDRURO) || defined(CONFIG_SMP)
+ asm("0: mrc p15, 0, %0, c13, c0, 3 \n\t"
+#ifdef CONFIG_CPU_V6
+ "1: \n\t"
+ " .subsection 1 \n\t"
+#if defined(CONFIG_ARM_HAS_GROUP_RELOCS) && \
+ !(defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
+ "2: " LOAD_SYM_ARMV6(%0, __current) " \n\t"
+ " b 1b \n\t"
+#else
+ "2: ldr %0, 3f \n\t"
+ " ldr %0, [%0] \n\t"
+ " b 1b \n\t"
+ "3: .long __current \n\t"
+#endif
+ " .previous \n\t"
+ " .pushsection \".alt.smp.init\", \"a\" \n\t"
+ " .long 0b - . \n\t"
+ " b . + (2b - 0b) \n\t"
+ " .popsection \n\t"
+#endif
+ : "=r"(cur));
+#elif __LINUX_ARM_ARCH__>= 7 || \
+ !defined(CONFIG_ARM_HAS_GROUP_RELOCS) || \
+ (defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS))
+ cur = __current;
+#else
+ asm(LOAD_SYM_ARMV6(%0, __current) : "=r"(cur));
+#endif
+ return cur;
+}
+
+#define current get_current()
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_ARM_CURRENT_H */