tools: riscv: Add header file vdso/processor.h

Borrow the cpu_relax() definitions from kernel's
arch/riscv/include/asm/vdso/processor.h to tools/ for riscv.

Signed-off-by: Haibo Xu <haibo1.xu@intel.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

diff --git a/tools/arch/riscv/include/asm/vdso/processor.h b/tools/arch/riscv/include/asm/vdso/processor.h
new file mode 100644 (file)
index 0000000..662aca0
--- /dev/null
+++ b/tools/arch/riscv/include/asm/vdso/processor.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __ASM_VDSO_PROCESSOR_H
+#define __ASM_VDSO_PROCESSOR_H
+
+#ifndef __ASSEMBLY__
+
+#include <asm-generic/barrier.h>
+
+static inline void cpu_relax(void)
+{
+#ifdef __riscv_muldiv
+       int dummy;
+       /* In lieu of a halt instruction, induce a long-latency stall. */
+       __asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
+#endif
+
+#ifdef CONFIG_TOOLCHAIN_HAS_ZIHINTPAUSE
+       /*
+        * Reduce instruction retirement.
+        * This assumes the PC changes.
+        */
+       __asm__ __volatile__ ("pause");
+#else
+       /* Encoding of the pause instruction */
+       __asm__ __volatile__ (".4byte 0x100000F");
+#endif
+       barrier();
+}
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __ASM_VDSO_PROCESSOR_H */