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, 83 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/riscv64/crt1.S b/libc/sysdeps/linux/riscv64/crt1.S
new file mode 100644
index 000000000..872e0b12e
--- /dev/null
+++ b/libc/sysdeps/linux/riscv64/crt1.S
@@ -0,0 +1,83 @@
+/* Startup code compliant to the ELF RISC-V ABI.
+   Copyright (C) 1995-2018 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.
+
+   In addition to the permissions in the GNU Lesser General Public
+   License, the Free Software Foundation gives you unlimited
+   permission to link the compiled version of this file with other
+   programs, and to distribute those programs without any restriction
+   coming from the use of this file. (The GNU Lesser General Public
+   License restrictions do apply in other respects; for example, they
+   cover modification of the file, and distribution when not linked
+   into another program.)
+
+   Note that people who make modified versions of this file are not
+   obligated to grant this special exception for their modified
+   versions; it is their choice whether to do so. The GNU Lesser
+   General Public License gives permission to release a modified
+   version without this exception; this exception also makes it
+   possible to release a modified version which carries forward this
+   exception.
+
+   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/>.  */
+
+#define __ASSEMBLY__ 1
+
+#include <sysdep.h>
+#include <sys/asm.h>
+
+/* The entry point's job is to call __uClibc_main.  Per the ABI,
+   a0 contains the address of a function to be passed to atexit.
+   __uClibc_main wants this in a5.  */
+
+.text
+	.globl	_start
+	.type	_start,%function
+
+_start:
+	call  .Lload_gp
+	mv    a5, a0  /* rtld_fini.  */
+	/* main may be in a shared library.  */
+	la   a0, main
+	REG_L a1, 0(sp)      /* argc.  */
+	addi  a2, sp, SZREG  /* argv.  */
+	andi  sp, sp, ALMASK /* Align stack. */
+	mv    a6, sp  /* stack_end.  */
+
+	tail  __uClibc_main@plt
+
+	.size	_start,.-_start
+
+/* Dynamic links need the global pointer to be initialized prior to calling
+   any shared library's initializers, so we use preinit_array to load it.
+   This doesn't cut it for static links, though, since the global pointer
+   needs to be initialized before calling __libc_start_main in that case.
+   So we redundantly initialize it at the beginning of _start.  */
+
+.Lload_gp:
+.option push
+.option norelax
+	lla   gp, __global_pointer$
+.option pop
+	ret
+
+	.section .preinit_array,"aw"
+	.dc.a .Lload_gp
+
+/* Define a symbol for the first piece of initialized data.  */
+	.data
+	.globl __data_start
+__data_start:
+	.weak data_start
+	data_start = __data_start