RISC-V: Task implementation

This patch contains the implementation of tasks on RISC-V, most of which
is involved in task switching.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/arch/riscv/include/asm/current.h b/arch/riscv/include/asm/current.h
new file mode 100644
index 000000000000..2cf6336ef600
--- /dev/null
+++ b/arch/riscv/include/asm/current.h
@@ -0,0 +1,45 @@
+/*
+ * Based on arm/arm64/include/asm/current.h
+ *
+ * Copyright (C) 2016 ARM
+ * Copyright (C) 2017 SiFive
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+
+#ifndef __ASM_CURRENT_H
+#define __ASM_CURRENT_H
+
+#include <linux/bug.h>
+#include <linux/compiler.h>
+
+#ifndef __ASSEMBLY__
+
+struct task_struct;
+
+/*
+ * This only works because "struct thread_info" is at offset 0 from "struct
+ * task_struct".  This constraint seems to be necessary on other architectures
+ * as well, but __switch_to enforces it.  We can't check TASK_TI here because
+ * <asm/asm-offsets.h> includes this, and I can't get the definition of "struct
+ * task_struct" here due to some header ordering problems.
+ */
+static __always_inline struct task_struct *get_current(void)
+{
+	register struct task_struct *tp __asm__("tp");
+	return tp;
+}
+
+#define current get_current()
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __ASM_CURRENT_H */