ELF startup code for Arm.

sysdeps/arm/elf/start.S

@@ -0,0 +1,109 @@
+/* Startup code for ARM & ELF
+   Copyright (C) 1995, 1996, 1997, 1998 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 Library General Public License as
+   published by the Free Software Foundation; either version 2 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  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.
+
+	Note that the code in the .init section has already been run.
+	This includes _init and _libc_init
+
+
+	At this entry point, most registers' values are unspecified, except for:
+
+   r0		Contains a function pointer to be registered with `atexit'.
+   		This is how the dynamic linker arranges to have DT_FINI
+		functions called for shared libraries that have been loaded
+		before this code runs.
+
+   sp		The stack contains the arguments and environment:
+   		0(%esp)			argc
+		4(%esp)			argv[0]
+		...
+		(4*argc)(%esp)		NULL
+		(4*(argc+1))(%esp)	envp[0]
+		...
+					NULL
+*/
+
+	.text
+	.globl _start
+_start:
+	/* Clear the frame pointer.  The Intel ABI suggests this be done,
+		to mark the outermost frame obviously. This seems like a
+		sensible thing to do  */
+	mov fp, #0
+
+	/* r0 contains the address of the shared library termination
+	   function, which we will register with `atexit' to be called by
+	   `exit'.  I suspect that on some systems, and when statically
+	   linked, this will not be set by anything to any function
+	   pointer; hopefully it will be zero so we don't try to call
+	   random pointers.  */
+	cmp r0,#0
+	blne atexit(PLT)
+
+	/* Do essential libc initialization.  In statically linked
+	   programs under the GNU Hurd, this is what sets up the
+	   arguments on the stack for the code below. For dyn-link
+	   programs, this has been run already, in the .init code. */
+#ifndef PIC
+	bl __libc_init_first
+
+	/* Extract the arguments and environment as encoded on the stack
+	   and set up the arguments for `main': argc, argv, envp.  */
+	ldr r0,[sp]
+	add r1,sp,#4
+	add r2,r1,r0,lsl #2
+	add r2,r2,#4
+	/* save a copy of envp while we have it */
+	ldr r3,L_environ
+	str r2,[r3]
+
+	/* Call `_init', which is the entry point to our own `.init'
+	   section; and register with `atexit' to have `exit' call
+	   `_fini', which is the entry point to our own `.fini' section.  */
+	bl _init
+	ldr r0,L_fini
+	bl atexit
+	b L_pfini
+
+L_fini:	.word _fini
+L_environ: .word _environ
+L_pfini:
+#endif
+	/* rebuild the arg list for main() */
+	ldr r0,[sp]
+	add r1,sp,#4
+	add r2,r1,r0,lsl #2
+	add r2,r2,#4
+
+	/* Call the user's main function, and exit with its value.  */
+	bl main
+	bl exit
+	/* should never get here....*/
+	bl abort
+
+
+/* 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