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rtld_start.S revision 1.8 
      1 /*	$NetBSD: rtld_start.S,v 1.8 2002/09/12 17:43:30 mycroft Exp $	*/
      2 
      3 /*
      4  * Copyright 1996 Matt Thomas <matt (at) 3am-software.com>
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. The name of the author may not be used to endorse or promote products
     16  *    derived from this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     28  */
     29 
     30 #include <machine/asm.h>
     31 
     32 	.data
     33 .L1:	.long	_GLOBAL_OFFSET_TABLE_
     34 
     35 /* R9 contains the address of PS_STRINGS and since its caller saved,
     36  * we can just use it.  R6 has a backup copy of the stack pointer which
     37  * we can use as well.  Since the VAX has perfectly PIC code, we don't
     38  * need to relocate anything upon startup.
     39  */
     40 ENTRY(_rtld_start, 0)
     41 	/* Allocate space on the stack for the cleanup and obj_main
     42 	 * entries that _rtld() will provide for us.
     43 	 */
     44 	clrl	%fp
     45 	subl2	$8,%sp
     46 
     47 	movab	_GLOBAL_OFFSET_TABLE_,%r0
     48 	subl2	.L1,%r0
     49 	movl	%sp,%r1
     50 	pushl	%r0		/* relocbase */
     51 	pushl	%r1		/* sp */
     52 	calls	$2,_rtld	/* entry = _rtld(sp, relocbase) */
     53 
     54 	movq	(%sp)+,%r7	/* grab cleanup and obj_main into %r7/%r8 */
     55 	jmp	2(%r0)		/* jump to entry point + 2 */
     56 
     57 /*
     58  * Lazy binding entry point, called via PLT.
     59  */
     60 ALTENTRY(_rtld_bind_start)
     61 	pushr	$0xff		/* save R0-R7 */
     62 	movq	32(%sp),%r0	/* get addresses of plt.got & reloc index */
     63 	pushl	(%r1)		/* push relocation index */
     64 	pushl	%r0		/* push address of obj entry */
     65 	calls	$2,_rtld_bind
     66 	movpsl	-(%sp)		/* flush the instruction cache */
     67 	pushab	1f		/*   by issuing an */
     68 	rei			/*   rei. */
     69 1:	movl	%r0,36(%sp)	/* save return address onto stack */
     70 2:	bicw3	6(%fp),(%r0),%r0	/* does the entry mask save any additional regs */
     71 	popr	$0xff		/* restore R0-R7 (cond flags not modified) */
     72 	bneq	4f		/* yes? do it the hard way */
     73 3:	addl2	$4,%sp		/* no? skip past plt.got on stack */
     74 	addl2	$2,(%sp)		/*    skip past the mask */
     75 	rsb			/*    and jump to it */
     76 4:	addl2	$4,%sp
     77 	callg	(%ap),*(%sp)+	/* return value from _rtld_bind() == actual */
     78 	ret
     79