3 files changed, 80 insertions, 0 deletions
diff --git a/arch/arm/include/asm/semihost.h b/arch/arm/include/asm/semihost.h
new file mode 100644
index 000000000000..f365787e7c23
--- /dev/null
+++ b/arch/arm/include/asm/semihost.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * Adapted for ARM and earlycon:
+ * Copyright (C) 2014 Linaro Ltd.
+ * Author: Rob Herring <robh@kernel.org>
+ */
+
+#ifndef _ARM_SEMIHOST_H_
+#define _ARM_SEMIHOST_H_
+
+#ifdef CONFIG_THUMB2_KERNEL
+#define SEMIHOST_SWI	"0xab"
+#else
+#define SEMIHOST_SWI	"0x123456"
+#endif
+
+struct uart_port;
+
+static inline void smh_putc(struct uart_port *port, unsigned char c)
+{
+	asm volatile("mov  r1, %0\n"
+		     "mov  r0, #3\n"
+		     "svc  " SEMIHOST_SWI "\n"
+		     : : "r" (&c) : "r0", "r1", "memory");
+}
+
+#endif /* _ARM_SEMIHOST_H_ */
diff --git a/arch/arm64/include/asm/semihost.h b/arch/arm64/include/asm/semihost.h
new file mode 100644
index 000000000000..87e353dab868
--- /dev/null
+++ b/arch/arm64/include/asm/semihost.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * Adapted for ARM and earlycon:
+ * Copyright (C) 2014 Linaro Ltd.
+ * Author: Rob Herring <robh@kernel.org>
+ */
+
+#ifndef _ARM64_SEMIHOST_H_
+#define _ARM64_SEMIHOST_H_
+
+struct uart_port;
+
+static inline void smh_putc(struct uart_port *port, unsigned char c)
+{
+	asm volatile("mov  x1, %0\n"
+		     "mov  x0, #3\n"
+		     "hlt  0xf000\n"
+		     : : "r" (&c) : "x0", "x1", "memory");
+}
+
+#endif /* _ARM64_SEMIHOST_H_ */
diff --git a/arch/riscv/include/asm/semihost.h b/arch/riscv/include/asm/semihost.h
new file mode 100644
index 000000000000..557a34938193
--- /dev/null
+++ b/arch/riscv/include/asm/semihost.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2022 tinylab.org
+ * Author: Bin Meng <bmeng@tinylab.org>
+ */
+
+#ifndef _RISCV_SEMIHOST_H_
+#define _RISCV_SEMIHOST_H_
+
+struct uart_port;
+
+static inline void smh_putc(struct uart_port *port, unsigned char c)
+{
+	asm volatile("addi    a1, %0, 0\n"
+		     "addi    a0, zero, 3\n"
+		     ".balign 16\n"
+		     ".option push\n"
+		     ".option norvc\n"
+		     "slli    zero, zero, 0x1f\n"
+		     "ebreak\n"
+		     "srai    zero, zero, 0x7\n"
+		     ".option pop\n"
+		     : : "r" (&c) : "a0", "a1", "memory");
+}
+
+#endif /* _RISCV_SEMIHOST_H_ */