risc-v: initial 64 bit port, static only (no TLS/NPTL)

Only a simple hello world is tested in qemu system emulation.

1 files changed, 80 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/riscv64/clone.S b/libc/sysdeps/linux/riscv64/clone.S
new file mode 100644
index 000000000..f7684c88d
--- /dev/null
+++ b/libc/sysdeps/linux/riscv64/clone.S
@@ -0,0 +1,80 @@
+/* Wrapper around clone system call.  RISC-V version.
+   Copyright (C) 1996-2018 Free Software Foundation, Inc.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* clone() is even more special than fork() as it mucks with stacks
+   and invokes a function in the right context after its all over.  */
+
+#include <sys/asm.h>
+#include <sysdep.h>
+#define _ERRNO_H	1
+#include <bits/errno.h>
+
+/* int clone(int (*fn)(void *arg), void *child_stack, int flags, void *arg,
+	     void *parent_tidptr, void *tls, void *child_tidptr) */
+
+	.text
+LEAF (clone)
+
+	/* Sanity check arguments.  */
+	beqz		a0,L (invalid)	/* No NULL function pointers.  */
+	beqz		a1,L (invalid)	/* No NULL stack pointers.  */
+
+	addi		a1,a1,-16	/* Reserve argument save space.  */
+	REG_S		a0,0(a1)	/* Save function pointer.  */
+	REG_S		a3,SZREG(a1)	/* Save argument pointer.  */
+
+	/* The syscall expects the args to be in different slots.  */
+	mv		a0,a2
+	mv		a2,a4
+	mv		a3,a5
+	mv		a4,a6
+
+	/* Do the system call.  */
+	li		a7,__NR_clone
+	scall
+
+	bltz		a0,L (error)
+	beqz		a0,L (thread_start)
+
+	/* Successful return from the parent.  */
+	ret
+
+L (invalid):
+	li		a0, -EINVAL
+	/* Something bad happened -- no child created.  */
+L (error):
+	j		__syscall_error
+	END (clone)
+
+/* Load up the arguments to the function.  Put this block of code in
+   its own function so that we can terminate the stack trace with our
+   debug info.  */
+
+ENTRY (__thread_start)
+L (thread_start):
+	/* Restore the arg for user's function.  */
+	REG_L		a1,0(sp)	/* Function pointer.  */
+	REG_L		a0,SZREG(sp)	/* Argument pointer.  */
+
+	/* Call the user's function.  */
+	jalr		a1
+
+	/* Call exit with the function's return value.  */
+	li		a7, __NR_exit
+	scall
+
+	END (__thread_start)