semihost: Implement UHI semihosting for MIPS

UHI is the semihosting protocol defined by MIPS.

It has been implemented in CodeScape and QEMU.

Signed-off-by: Jiaxun Yang <[email protected]>

Author: FlyGoat

semihost/machine/mips/meson.build

@@ -2,6 +2,7 @@
 # SPDX-License-Identifier: BSD-3-Clause
 #
 # Copyright © 2021 Keith Packard
+# Copyright © 2025 Jiaxun Yang <[email protected]>
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
@@ -32,12 +33,17 @@
 # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 # OF THE POSSIBILITY OF SUCH DAMAGE.
 #
-
 lib_semihost_srcs = [
-  'mips_stub.c',
+  'mips_close.c',
   'mips_exit.c',
-  'mips_iob.c',
-  ]
+  'mips_fstat.c',
+  'mips_lseek.c',
+  'mips_open.c',
+  'mips_read.c',
+  'mips_stub.c',
+  'mips_unlink.c',
+  'mips_write.c',
+]
 
 has_semihost = true
 
@@ -62,4 +68,3 @@ foreach params : targets
   set_variable('lib_semihost' + target, local_lib_semihost_target)
 
 endforeach
-

semihost/machine/mips/mips_close.c

@@ -0,0 +1,44 @@
+/*
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright © 2025 Jiaxun Yang <[email protected]>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials provided
+ *    with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "mips_semihost.h"
+#include <sys/cdefs.h>
+#include <unistd.h>
+
+int
+close(int fd)
+{
+    return mips_semihost1(SYS_SEMIHOST_close, fd);
+}

semihost/machine/mips/mips_exit.c

@@ -1,7 +1,7 @@
 /*
  * SPDX-License-Identifier: BSD-3-Clause
  *
- * Copyright © 2021 Keith Packard
+ * Copyright © 2025 Jiaxun Yang <[email protected]>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -33,15 +33,13 @@
  * OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include "mips-semihost.h"
+#include "mips_semihost.h"
+#include <sys/cdefs.h>
+#include <unistd.h>
 
 _Noreturn void
 _exit(int code)
 {
-        char buf[15];
-        int n;
-        /* Can't use printf because stdout has already been cleaned up */
-        n = snprintf(buf, sizeof(buf), "%cexit %d\n", 0xe9, code);
-        write(1, buf, n);
-	while(1);
+    mips_semihost1(SYS_SEMIHOST_exit, code);
+    __unreachable();
 }

semihost/machine/mips/mips_fstat.c

@@ -0,0 +1,60 @@
+/*
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright © 2025 Jiaxun Yang <[email protected]>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials provided
+ *    with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-Wpragmas"
+/* False positive for mips_stat */
+#pragma GCC diagnostic ignored "-Wanalyzer-use-of-uninitialized-value"
+#endif
+
+#include "mips_semihost.h"
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <stdarg.h>
+
+int
+fstat(int fd, struct stat *restrict statbuf)
+{
+    struct mips_stat mips_stat;
+    int ret;
+
+    ret = mips_semihost2(SYS_SEMIHOST_fstat, fd, (uintptr_t)&mips_stat);
+    if (ret >= 0)
+        copy_stat(statbuf, &mips_stat);
+
+    return ret;
+}

semihost/machine/mips/mips_iob.c

@@ -0,0 +1,50 @@
+/*
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright © 2025 Jiaxun Yang <[email protected]>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials provided
+ *    with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "mips_semihost.h"
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+
+off_t
+lseek(int fd, off_t offset, int whence)
+{
+    off_t ret = mips_semihost3(SYS_SEMIHOST_lseek, fd, offset, whence);
+
+    return ret;
+}