lib: Linux riscv64-mes-mescc support.

* lib/linux/riscv64-mes-mescc/_exit.c,
lib/linux/riscv64-mes-mescc/_write.c,
lib/linux/riscv64-mes-mescc/crt1.c,
lib/linux/riscv64-mes-mescc/syscall-internal.c,
lib/linux/riscv64-mes-mescc/syscall.c: New files.  These add support for
building for riscv64-mes-mescc and make it self-hosting.

lib/linux/riscv64-mes-mescc/_exit.c

@@ -0,0 +1,31 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2018,2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2021 W. J. van der Laan <laanwj@protonmail.com>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "mes/lib-mini.h"
+
+void
+_exit (int status)
+{
+  asm ("ld_____%a0,0x10(%fp)");
+  asm ("li_____%a7,SYS_exit");
+  asm ("ecall");
+  // no need to read return value
+}

lib/linux/riscv64-mes-mescc/_write.c

@@ -0,0 +1,33 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2018,2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2021 W. J. van der Laan <laanwj@protonmail.com>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "mes/lib-mini.h"
+
+void
+_write (int filedes, void const *buffer, size_t size)
+{
+  asm ("ld_____%a0,0x10(%fp)");
+  asm ("ld_____%a1,0x18(%fp)");
+  asm ("ld_____%a2,0x20(%fp)");
+  asm ("li_____%a7,SYS_write");
+  asm ("ecall");
+  asm ("mv_____%t0,%a0");
+}

lib/linux/riscv64-mes-mescc/crt1.c

@@ -0,0 +1,70 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2021 W. J. van der Laan <laanwj@protonmail.com>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "mes/lib-mini.h"
+int main (int argc, char *argv[], char *envp[]);
+
+/* mesc will generate the following preamble:
+
+   push    ra
+   push    fp
+*/
+int
+_start ()
+{
+  asm ("li_____%t0,$i16_0000 @0");
+  asm ("li_____%t1,$i32 &__stdin");
+  asm ("sw_____%t0,0(%t1)");
+
+  asm ("li_____%t0,$i16_0000 @1");
+  asm ("srai___%t0,16");
+  asm ("li_____%t1,$i32 &__stdout");
+  asm ("sw_____%t0,0(%t1)");
+
+  asm ("li_____%t0,$i16_0000 @2");
+  asm ("srai___%t0,16");
+  asm ("li_____%t1,$i32 &__stderr");
+  asm ("sw_____%t0,0(%t1)");
+
+  // environ is &argv[argc + 1]
+  asm ("mv_____%t1,%fp");
+  asm ("addi___%t1,%t1,$i8_8 !0x1"); // 0x10 to skip over pushed fp+ra, 0x8 to skip over argc
+  asm ("addi___%t5,%fp,$i8_0 !0x1"); // 0x10 to skip over pushed fp+ra
+  asm ("ld_____%t0,0(%t5)");
+  asm ("addi___%t0,%t0,1");
+  asm ("li_____%t5,$i32 %0x3"); // skip over all arguments and the final NULL
+  asm ("sll____%t0,%t0,%t5");
+  asm ("add____%t0,%t0,%t1");
+  asm ("push___%t0"); // envp
+  asm ("push___%t1"); // argv
+  asm ("li_____%t1,$i32 &environ");
+  asm ("sd_____%t0,0(%t1)");
+  asm ("addi___%t5,%fp,$i8_0 !0x1"); // 0x10 to skip over pushed fp+ra
+  asm ("ld_____%t0,0(%t5)");
+  asm ("push___%t0"); // argc
+
+  main ();
+
+  asm ("mv_____%a0,%t0");
+  asm ("li_____%a7,SYS_exit");
+  asm ("ecall");
+  asm ("ebreak");
+}

lib/linux/riscv64-mes-mescc/syscall-internal.c

@@ -0,0 +1,56 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2016,2017,2018,2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2021 W. J. van der Laan <laanwj@protonmail.com>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <errno.h>
+#include <linux/riscv64/syscall.h>
+
+static long
+__sys_call_internal (long sys_call)
+{
+  asm ("ld_____%a7,0x10(%fp)");
+
+  asm ("ecall");
+
+  asm ("mv_____%t0,%a0");
+}
+
+static long
+__sys_call2_internal (long sys_call, long one, long two)
+{
+  asm ("ld_____%a7,0x10(%fp)");
+  asm ("ld_____%a0,0x18(%fp)");
+  asm ("ld_____%a1,0x20(%fp)");
+
+  asm ("ecall");
+
+  asm ("mv_____%t0,%a0");
+}
+
+/* Return < 0 on error (errno-like value from kernel), or 0 on success */
+int
+__raise (int signum)
+{
+  long pid = __sys_call_internal (SYS_getpid);
+  if (pid < 0)
+    return pid;
+  else
+    return __sys_call2_internal (SYS_kill, pid, signum);
+}

lib/linux/riscv64-mes-mescc/syscall.c

@@ -0,0 +1,182 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2016,2017,2018,2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2021 W. J. van der Laan <laanwj@protonmail.com>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <errno.h>
+#include <linux/riscv64/syscall.h>
+
+long
+__sys_call (long sys_call)
+{
+  asm ("ld_____%a7,0x10(%fp)");
+
+  asm ("ecall");
+
+  asm ("mv_____%t0,%a0");
+}
+
+long
+__sys_call1 (long sys_call, long one)
+{
+  asm ("ld_____%a7,0x10(%fp)");
+  asm ("ld_____%a0,0x18(%fp)");
+
+  asm ("ecall");
+
+  asm ("mv_____%t0,%a0");
+}
+
+long
+__sys_call2 (long sys_call, long one, long two)
+{
+  asm ("ld_____%a7,0x10(%fp)");
+  asm ("ld_____%a0,0x18(%fp)");
+  asm ("ld_____%a1,0x20(%fp)");
+
+  asm ("ecall");
+
+  asm ("mv_____%t0,%a0");
+}
+
+long
+__sys_call3 (long sys_call, long one, long two, long three)
+{
+  asm ("ld_____%a7,0x10(%fp)");
+  asm ("ld_____%a0,0x18(%fp)");
+  asm ("ld_____%a1,0x20(%fp)");
+  asm ("ld_____%a2,0x28(%fp)");
+
+  asm ("ecall");
+
+  asm ("mv_____%t0,%a0");
+}
+
+long
+__sys_call4 (long sys_call, long one, long two, long three, long four)
+{
+  asm ("ld_____%a7,0x10(%fp)");
+  asm ("ld_____%a0,0x18(%fp)");
+  asm ("ld_____%a1,0x20(%fp)");
+  asm ("ld_____%a2,0x28(%fp)");
+  asm ("ld_____%a3,0x30(%fp)");
+
+  asm ("ecall");
+
+  asm ("mv_____%t0,%a0");
+}
+
+long
+__sys_call5 (long sys_call, long one, long two, long three, long four, long five)
+{
+  asm ("ld_____%a7,0x10(%fp)");
+  asm ("ld_____%a0,0x18(%fp)");
+  asm ("ld_____%a1,0x20(%fp)");
+  asm ("ld_____%a2,0x28(%fp)");
+  asm ("ld_____%a3,0x30(%fp)");
+  asm ("ld_____%a4,0x38(%fp)");
+
+  asm ("ecall");
+
+  asm ("mv_____%t0,%a0");
+}
+
+long
+_sys_call (long sys_call)
+{
+  long r = __sys_call (sys_call);
+  if (r < 0)
+    {
+      errno = -r;
+      r = -1;
+    }
+  else
+    errno = 0;
+  return r;
+}
+
+long
+_sys_call1 (long sys_call, long one)
+{
+  long r = __sys_call1 (sys_call, one);
+  if (r < 0)
+    {
+      errno = -r;
+      r = -1;
+    }
+  else
+    errno = 0;
+  return r;
+}
+
+long
+_sys_call2 (long sys_call, long one, long two)
+{
+  long r = __sys_call2 (sys_call, one, two);
+  if (r < 0)
+    {
+      errno = -r;
+      r = -1;
+    }
+  else
+    errno = 0;
+  return r;
+}
+
+long
+_sys_call3 (long sys_call, long one, long two, long three)
+{
+  long r = __sys_call3 (sys_call, one, two, three);
+  if (r < 0)
+    {
+      errno = -r;
+      r = -1;
+    }
+  else
+    errno = 0;
+  return r;
+}
+
+long
+_sys_call4 (long sys_call, long one, long two, long three, long four)
+{
+  long r = __sys_call4 (sys_call, one, two, three, four);
+  if (r < 0)
+    {
+      errno = -r;
+      r = -1;
+    }
+  else
+    errno = 0;
+  return r;
+}
+
+long
+_sys_call5 (long sys_call, long one, long two, long three, long four, long five)
+{
+  long r = __sys_call5 (sys_call, one, two, three, four, five);
+  if (r < 0)
+    {
+      errno = -r;
+      r = -1;
+    }
+  else
+    errno = 0;
+  return r;
+}