arm64: add cycles.h

Required for get_cycles() in userspace. This is required to compile
the tools. Whether or not get_cycles() works in userspace depends on
whether the kernel has enabled access to the CNTVCT_EL0 register from
userspace (= exception level EL0).

1 files changed, 20 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/cycles.h b/arch/arm64/include/asm/cycles.h
new file mode 100644
index 0000000..e832d82
--- /dev/null
+++ b/arch/arm64/include/asm/cycles.h
@@ -0,0 +1,20 @@
+#ifndef ASM_CYCLES_H
+#define ASM_CYCLES_H
+
+#include <stdint.h>
+#include <inttypes.h>
+
+typedef uint64_t cycles_t;
+
+#define CYCLES_FMT PRIu64
+
+static inline cycles_t get_cycles(void)
+{
+        cycles_t c;
+        asm volatile(
+                "isb\n"
+                "mrs %0, cntvct_el0" : "=r" (c));
+        return c;
+}
+
+#endif