thermosphere: add semihosting support & load a kernel using it when needed

basically host i/o

thermosphere/src/semihosting.h

@@ -0,0 +1,65 @@
+#pragma once
+
+// Adapted from Arm TF
+
+/*
+ * Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdint.h>
+#include <stdio.h> /* For ssize_t */
+
+
+#define SEMIHOSTING_SYS_OPEN            0x01
+#define SEMIHOSTING_SYS_CLOSE           0x02
+#define SEMIHOSTING_SYS_WRITE0          0x04
+#define SEMIHOSTING_SYS_WRITEC          0x03
+#define SEMIHOSTING_SYS_WRITE           0x05
+#define SEMIHOSTING_SYS_READ            0x06
+#define SEMIHOSTING_SYS_READC           0x07
+#define SEMIHOSTING_SYS_SEEK            0x0A
+#define SEMIHOSTING_SYS_FLEN            0x0C
+#define SEMIHOSTING_SYS_REMOVE          0x0E
+#define SEMIHOSTING_SYS_SYSTEM          0x12
+#define SEMIHOSTING_SYS_ERRNO           0x13
+
+#define FOPEN_MODE_R            0x0
+#define FOPEN_MODE_RB           0x1
+#define FOPEN_MODE_RPLUS        0x2
+#define FOPEN_MODE_RPLUSB       0x3
+#define FOPEN_MODE_W            0x4
+#define FOPEN_MODE_WB           0x5
+#define FOPEN_MODE_WPLUS        0x6
+#define FOPEN_MODE_WPLUSB       0x7
+#define FOPEN_MODE_A            0x8
+#define FOPEN_MODE_AB           0x9
+#define FOPEN_MODE_APLUS        0xa
+#define FOPEN_MODE_APLUSB       0xb
+
+static inline long semihosting_connection_supported(void)
+{
+#ifdef PLATFORM_QEMU
+    return 1;
+#else
+    return 0;
+#endif
+}
+
+long semihosting_file_open(const char *file_name, size_t mode);
+long semihosting_file_seek(long file_handle, ssize_t offset);
+long semihosting_file_read(long file_handle, size_t *length, uintptr_t buffer);
+long semihosting_file_write(long file_handle,
+                size_t *length,
+                const uintptr_t buffer);
+long semihosting_file_close(long file_handle);
+long semihosting_file_length(long file_handle);
+long semihosting_system(char *command_line);
+long semihosting_get_flen(const char *file_name);
+long semihosting_download_file(const char *file_name,
+                   size_t buf_size,
+                   uintptr_t buf);
+void semihosting_write_char(char character);
+void semihosting_write_string(const char *string);
+char semihosting_read_char(void);