drivers: Implement semihosting based console driver for log

Implement a simple console driver which uses semihosting operations to
read/write the trace messages. There are two paths to output the trace
messages:
- If the caller of semihosting_console_init() provides the path of the
  file, the driver will try to open that file, and output the log to
  that host side file.
- If the caller of semihosting_console_init() does not provide the path
  of the file, the driver will connect the console to the host debug
  console directly.

If CFG_SEMIHOSTING_CONSOLE is enabled, OP-TEE will try to initialize the
semihosting console driver by given CFG_SEMIHOSTING_CONSOLE_FILE.

Signed-off-by: Alvin Chang <[email protected]>
Acked-by: Jerome Forissier <[email protected]>
Reviewed-by: Jens Wiklander <[email protected]>

core/drivers/semihosting_console.c

@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: BSD-2-Clause
+/*
+ * Copyright (c) 2024 Andes Technology Corporation
+ */
+
+#include <compiler.h>
+#include <console.h>
+#include <drivers/semihosting_console.h>
+#include <drivers/serial.h>
+#include <kernel/semihosting.h>
+#include <util.h>
+
+/*
+ * struct semihosting_console_data - Structure for semihosting console driver
+ * @chip - General structure for each serial chip
+ * @fd - Handle of the file at @file_path when semihosting_console_init() is
+ *       called, or -1 if using the semihosting console
+ */
+struct semihosting_console_data {
+	struct serial_chip chip;
+	int fd;
+};
+
+static struct semihosting_console_data sh_console_data __nex_bss;
+
+static void semihosting_console_putc(struct serial_chip *chip __unused, int ch)
+{
+	semihosting_sys_writec(ch);
+}
+
+static int semihosting_console_getchar(struct serial_chip *chip __unused)
+{
+	return semihosting_sys_readc();
+}
+
+static const struct serial_ops semihosting_console_ops = {
+	.putc = semihosting_console_putc,
+	.getchar = semihosting_console_getchar,
+};
+DECLARE_KEEP_PAGER(semihosting_console_ops);
+
+static void semihosting_console_fd_putc(struct serial_chip *chip __unused,
+					int ch)
+{
+	if (sh_console_data.fd >= 0)
+		semihosting_write(sh_console_data.fd, &ch, 1);
+}
+
+static const struct serial_ops semihosting_console_fd_ops = {
+	.putc = semihosting_console_fd_putc,
+};
+DECLARE_KEEP_PAGER(semihosting_console_fd_ops);
+
+void semihosting_console_init(const char *file_path)
+{
+	if (file_path) {
+		/* Output log to given file on the semihosting host system. */
+		sh_console_data.chip.ops = &semihosting_console_fd_ops;
+		sh_console_data.fd =
+			semihosting_open(file_path, O_RDWR | O_CREAT | O_TRUNC);
+	} else {
+		/* Output log to semihosting host debug console. */
+		sh_console_data.chip.ops = &semihosting_console_ops;
+		sh_console_data.fd = -1;
+	}
+
+	register_serial_console(&sh_console_data.chip);
+}

core/drivers/sub.mk

@@ -79,6 +79,7 @@ srcs-$(CFG_CBMEM_CONSOLE) += cbmem_console.c
 srcs-$(CFG_RISCV_PLIC) += plic.c
 srcs-$(CFG_HISILICON_CRYPTO_DRIVER) += hisi_trng.c
 srcs-$(CFG_WIDEVINE_HUK) += widevine_huk.c
+srcs-$(CFG_SEMIHOSTING_CONSOLE) += semihosting_console.c
 
 subdirs-y += crypto
 subdirs-$(CFG_BNXT_FW) += bnxt

core/include/drivers/semihosting_console.h

@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (c) 2024 Andes Technology Corporation
+ */
+#ifndef __DRIVERS_SEMIHOSTING_CONSOLE_H
+#define __DRIVERS_SEMIHOSTING_CONSOLE_H
+
+#ifdef CFG_SEMIHOSTING_CONSOLE
+/*
+ * Initialize console which uses architecture-specific semihosting mechanism.
+ * If @file_path is not NULL, OP-TEE OS will try to output log to that file,
+ * which is on the semihosting host system.
+ * Otherwise, if @file_path is NULL, OP-TEE OS will try to output log to the
+ * semihosting host debug console.
+ */
+void semihosting_console_init(const char *file_path);
+#else
+static inline void semihosting_console_init(const char *file_path __unused)
+{
+}
+#endif
+
+#endif /* __DRIVERS_SEMIHOSTING_CONSOLE_H */

core/kernel/console.c

@@ -6,6 +6,7 @@
 #include <compiler.h>
 #include <console.h>
 #include <drivers/cbmem_console.h>
+#include <drivers/semihosting_console.h>
 #include <drivers/serial.h>
 #include <kernel/dt.h>
 #include <kernel/dt_driver.h>
@@ -24,7 +25,10 @@ __weak void plat_console_init(void)
 
 void console_init(void)
 {
-	plat_console_init();
+	if (IS_ENABLED(CFG_SEMIHOSTING_CONSOLE))
+		semihosting_console_init(CFG_SEMIHOSTING_CONSOLE_FILE);
+	else
+		plat_console_init();
 }
 
 void __weak console_putc(int ch)

mk/config.mk

@@ -1159,6 +1159,20 @@ $(eval $(call cfg-depends-all,CFG_WIDEVINE_HUK,CFG_DT))
 CFG_WIDEVINE_PTA ?= n
 $(eval $(call cfg-depends-all,CFG_WIDEVINE_PTA,CFG_DT CFG_WIDEVINE_HUK))
 
+# CFG_SEMIHOSTING_CONSOLE, when enabled, embeds a semihosting console driver.
+# When CFG_SEMIHOSTING_CONSOLE_FILE=NULL, OP-TEE console reads/writes
+# trace messages from/to the debug terminal of the semihosting host computer.
+# When CFG_SEMIHOSTING_CONSOLE_FILE="{your_log_file}", OP-TEE console
+# outputs trace messages to that file. Output to "optee.log" by default.
+CFG_SEMIHOSTING_CONSOLE ?= n
+ifeq ($(CFG_SEMIHOSTING_CONSOLE),y)
+$(call force,CFG_SEMIHOSTING,y)
+endif
+CFG_SEMIHOSTING_CONSOLE_FILE ?= "optee.log"
+ifeq ($(CFG_SEMIHOSTING_CONSOLE_FILE),)
+$(error CFG_SEMIHOSTING_CONSOLE_FILE cannot be empty)
+endif
+
 # Semihosting is a debugging mechanism that enables code running on an embedded
 # system (also called the target) to communicate with and use the I/O of the
 # host computer.