1/* Startup code compliant to the ELF m68k ABI.
  2   Copyright (C) 1996-2020 Free Software Foundation, Inc.
  3   This file is part of the GNU C Library.
  4
  5   The GNU C Library is free software; you can redistribute it and/or
  6   modify it under the terms of the GNU Lesser General Public
  7   License as published by the Free Software Foundation; either
  8   version 2.1 of the License, or (at your option) any later version.
  9
 10   In addition to the permissions in the GNU Lesser General Public
 11   License, the Free Software Foundation gives you unlimited
 12   permission to link the compiled version of this file with other
 13   programs, and to distribute those programs without any restriction
 14   coming from the use of this file. (The GNU Lesser General Public
 15   License restrictions do apply in other respects; for example, they
 16   cover modification of the file, and distribution when not linked
 17   into another program.)
 18
 19   Note that people who make modified versions of this file are not
 20   obligated to grant this special exception for their modified
 21   versions; it is their choice whether to do so. The GNU Lesser
 22   General Public License gives permission to release a modified
 23   version without this exception; this exception also makes it
 24   possible to release a modified version which carries forward this
 25   exception.
 26
 27   The GNU C Library is distributed in the hope that it will be useful,
 28   but WITHOUT ANY WARRANTY; without even the implied warranty of
 29   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 30   Lesser General Public License for more details.
 31
 32   You should have received a copy of the GNU Lesser General Public
 33   License along with the GNU C Library.  If not, see
 34   <https://www.gnu.org/licenses/>.  */
 35
 36/* This is the canonical entry point, usually the first thing in the text
 37   segment.  The SVR4/m68k ABI says that when the entry point runs,
 38   most registers' values are unspecified, except for:
 39
 40   %a1		Contains a function pointer to be registered with `atexit'.
 41		This is how the dynamic linker arranges to have DT_FINI
 42		functions called for shared libraries that have been loaded
 43		before this code runs.
 44
 45   %sp		The stack contains the arguments and environment:
 46		0(%sp)			argc
 47		4(%sp)			argv[0]
 48		...
 49		(4*argc)(%sp)		NULL
 50		(4*(argc+1))(%sp)	envp[0]
 51		...
 52					NULL
 53*/
 54
 55#include <sysdep.h>
 56
 57	.text
 58	.globl _start
 59	.type _start,@function
 60_start:
 61	/* Clear the frame pointer.  The ABI suggests this be done, to mark
 62	   the outermost frame obviously.  */
 63	sub.l %fp, %fp
 64
 65	/* Extract the arguments as encoded on the stack and set up the
 66	   arguments for `main': argc, argv.  envp will be determined
 67	   later in __libc_start_main.  */
 68	move.l (%sp)+, %d0	/* Pop the argument count.  */
 69	move.l %sp, %a0		/* The argument vector starts just at the
 70				   current stack top.  */
 71
 72	/* Provide the highest stack address to the user code (for stacks
 73	   which grow downward).  */
 74	pea (%sp)
 75
 76	pea (%a1)		/* Push address of the shared library
 77				   termination function.  */
 78
 79#ifdef PIC
 80	/* Load PIC register.  */
 81	LOAD_GOT (%a5)
 82
 83	/* Push the address of our own entry points to `.fini' and
 84	   `.init'.  */
 85	move.l __libc_csu_fini@GOT(%a5), -(%sp)
 86	move.l __libc_csu_init@GOT(%a5), -(%sp)
 87
 88	pea (%a0)		/* Push second argument: argv.  */
 89	move.l %d0, -(%sp)	/* Push first argument: argc.  */
 90
 91	move.l main@GOT(%a5), -(%sp)
 92
 93	/* Call the user's main function, and exit with its value.  But
 94	   let the libc call main.  */
 95	jbsr __libc_start_main@PLTPC
 96#else
 97	/* Push the address of our own entry points to `.fini' and
 98	   `.init'.  */
 99	pea __libc_csu_fini
100	pea __libc_csu_init
101
102	pea (%a0)		/* Push second argument: argv.  */
103	move.l %d0, -(%sp)	/* Push first argument: argc.  */
104
105	pea main
106
107	/* Call the user's main function, and exit with its value.  But
108	   let the libc call main.  */
109	jbsr __libc_start_main
110#endif
111
112	illegal			/* Crash if somehow `exit' does return.  */
113
114/* Define a symbol for the first piece of initialized data.  */
115	.data
116	.globl __data_start
117__data_start:
118	.long 0
119	.weak data_start
120	data_start = __data_start