glibc/sysdeps/or1k/start.S

/* start, OpenRISC version.
   Copyright (C) 2022-2024 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.

   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
   <https://www.gnu.org/licenses/>.  */

/* 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