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rtld_start.S revision 1.1 
      1 /* $NetBSD: rtld_start.S,v 1.1 2014/08/10 05:47:37 matt Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 2014 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Matt Thomas of 3am Software Foundry.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <machine/asm.h>
     33 
     34 RCSID("$NetBSD: rtld_start.S,v 1.1 2014/08/10 05:47:37 matt Exp $")
     35 
     36 /*
     37  * void _rtld_start(void (*cleanup)(void), const Obj_Entry *obj,
     38  *    struct ps_strings *ps_strings);
     39  *
     40  * X0		= NULL
     41  * X1		= NULL
     42  * X2		= ps_strings
     43  * X30 (LR)	= 0
     44  * X29 (FP)	= 0
     45  */
     46 
     47 ENTRY_NP(_rtld_start)
     48 	mov	x24, x2			/* save ps_strings */
     49 
     50 #if 1
     51 	adrp	x1, _PROCEDURE_LINKAGE_TABLE_	/* load _DYNAMIC offset from GOT */
     52 	ldr	x1, [x1, #:got_lo12:_PROCEDURE_LINKAGE_TABLE_]
     53 #else
     54 	adrp	x1, :got:_DYNAMIC	/* load _DYNAMIC offset from GOT */
     55 	ldr	x1, [x1, #:got_lo12:_DYNAMIC]
     56 #endif
     57 
     58 	adrp	x0, _DYNAMIC		/* get &_DYNAMIC */
     59 	add	x0, x0, #:lo12:_DYNAMIC
     60 	sub	x25, x0, x1		/* relocbase = &_DYNAMIC - GOT:_DYNAMIC */
     61 	mov	x1, x25			/* pass as 2nd argument */
     62 	bl	_rtld_relocate_nonplt_self
     63 
     64 	sub	sp, sp, #16		/* reserve space for returns */
     65 	mov	x0, sp			/* pointer to reserved space */
     66 	mov	x1, x25			/* pass relocbase */
     67 	bl	_rtld
     68 	mov	x17, x0			/* save entry point */
     69 
     70 	ldp	x0, x1, [sp], #16	/* pop cleanup & obj_main */
     71 	mov	x2, x24			/* restore ps_strings */
     72 
     73 	br	x17			/* call saved entry point */
     74 END(_rtld_start)
     75 
     76 /*
     77  * Upon entry from plt0 entry:
     78  * X17 = &PLTGOT[n]
     79  * X16 = &PLTGOT[2]
     80  */
     81 ENTRY_NP(_rtld_bind_start)
     82 	sub	sp, sp, #96		/* reserve stack space */
     83 	stp	x29, x30, [sp, #80]	/* save FP & LR */
     84 	add	x29, sp, #80		/* get new FP */
     85 	str	x24, [sp, #64]		/* save caller-saved register */
     86 	stp	x6, x7, [sp, #48]	/* save arguments */
     87 	stp	x4, x5, [sp, #32]	/* save arguments */
     88 	stp	x2, x3, [sp, #16]	/* save arguments */
     89 	stp	x0, x1, [sp, #0]	/* save arguments */
     90 
     91 	sub	x16, x16, #16		/* adjust to &PLTGOT[0] */
     92 	mov	x24, x17		/* preserve across _rtld_bind */
     93 	sub	x1, x17, x16		/* x1 = &PLTGOT[N] - &PLTGOT[2] */
     94 	lsr	x1, x1, #3		/* x1 = N - 2 */
     95 	ldr	x0, [x16, #8]		/* get obj ptr from &PLTGOT[1] */
     96 	bl	_rtld_bind
     97 	str	x0, [x24]		/* save address in PLTGOT[N] */
     98 	mov	x17, x0			/* save address */
     99 
    100 	ldp	x0, x1, [sp, #0]	/* restore arguments */
    101 	ldp	x2, x3, [sp, #16]	/* restore arguments */
    102 	ldp	x4, x5, [sp, #32]	/* restore arguments */
    103 	ldp	x6, x7, [sp, #48]	/* restore arguments */
    104 	ldr	x24, [sp, #64]		/* save caller-saved register */
    105 	ldp	x29, x30, [sp, #80]	/* restore FP & LR */
    106 	add	sp, sp, #96		/* reclaim stack */
    107 	br	x17			/* call bound function */
    108 END(_rtld_bind_start)
    109