or1k: startup and dynamic linking code

Code for C runtime startup and dynamic loading including PLT layout.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 99 insertions, 0 deletions

diff --git a/sysdeps/or1k/start.S b/sysdeps/or1k/start.S
new file mode 100644
index 0000000..3577fc9
--- /dev/null
+++ b/sysdeps/or1k/start.S
@@ -0,0 +1,99 @@
+/* start, OpenRISC version.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+/* This is the canonical entry point, usually the first thing in the text
+   segment.
+
+   sp   The stack contains the arguments and environment:
+    0(sp)     argc
+    4(sp)     argv[0]
+    ...
+    (4*argc)(sp)    NULL
+    (4*(argc+1))(sp)  envp[0]
+    ...
+    NULL
+ */
+
+#define __ASSEMBLY__
+#include <sysdep.h>
+#include <entry.h>
+
+ENTRY (ENTRY_POINT)
+
+	/* Setup Arguments to the __libc_start_main function.  */
+
+	/* Take values for argc and argv off the stack.
+	   These will be passed as arguments two and three to main
+	   and thus go in registers r4 and r5, respectively.  */
+	l.lwz	r4, 0(r1)
+	l.addi	r5, r1, 4
+
+	/* Pass in rtld_fini from dl-start.S.  */
+	l.or	r8, r3, r3
+
+#ifdef PIC
+	/* Obtain a pointer to .got in r16 */
+	l.jal	0x8
+	 l.movhi r16, gotpchi(_GLOBAL_OFFSET_TABLE_-4)
+	l.ori	r16, r16, gotpclo(_GLOBAL_OFFSET_TABLE_+0)
+	l.add	r16, r16, r9
+
+	/* Pass in the the main symbol.  */
+	l.lwz	r3, got(main)(r16)
+#else
+	/* Pass in the the main symbol.  */
+	l.movhi r3, hi(main)
+	l.ori	r3, r3, lo(main)
+#endif
+	/* Used to be init and fini.  */
+	l.movhi	r6, 0x0
+	l.movhi	r7, 0x0
+
+	/* Push stack limit onto the stack.
+	   This provides the highest stack address to user code (as stack grows
+	   downwards.
+	   This is the seventh argument to __libc_start_main and thus needs to
+	   be passed on the stack.  */
+	l.sw	-4(r1), r1
+
+	/* Adjust stack to account for a total of 7 args (i.e. the last one is
+	   on the stack.  */
+	l.addi	r1, r1, -4
+
+	/* Clear the frame pointer and link register since this is the
+	   outermost frame.  */
+	l.movhi	r2, 0x0
+	l.movhi	r9, 0x0
+
+	/* Let the libc call main and exit with its return code.  */
+#ifdef PIC
+	l.j	plt(__libc_start_main)
+#else
+	l.j	__libc_start_main
+#endif
+	 l.nop
+END (ENTRY_POINT)
+
+	/* Define a symbol for the first piece of initialized data.  */
+	.data
+	.globl __data_start
+__data_start:
+	.long 0
+	.weak data_start
+	data_start = __data_start