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rtld_start.S revision 1.6 
      1 /*	$NetBSD: rtld_start.S,v 1.6 2023/05/07 12:41:48 skrll 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 	.globl _C_LABEL(_rtld_relocate_nonplt_self)
     35 	.globl _C_LABEL(_rtld)
     36 
     37 #define PTRSZ	__SIZEOF_POINTER__
     38 
     39 /*
     40  * void
     41  * ___start(
     42  *     void (*cleanup)(void),
     43  *     struct ps_strings *ps_strings
     44  * )
     45  */
     46 
     47 ENTRY(_rtld_start)
     48 	mv	s0, sp			# save stack pointer
     49 	addi	sp, sp, -4 * PTRSZ	# adjust stack pointer
     50 					# -> 2 * PTR_SIZE(sp) for atexit
     51 					# -> 3 * PTR_SIZE(sp) for obj_main
     52 	mv	s1, a1			# save ps_strings pointer
     53 
     54 .L0:	auipc	gp, %pcrel_hi(_GLOBAL_OFFSET_TABLE_)
     55 	PTR_L	t0, %pcrel_lo(.L0)(gp) # &_DYNAMIC
     56 .L1:	auipc	a0, %pcrel_hi(_DYNAMIC)
     57 	addi	a0, a0, %pcrel_lo(.L1)
     58 	sub	s2, a0, t0		# save for _rtld
     59 	mv	a1, s2
     60 	call	_C_LABEL(_rtld_relocate_nonplt_self)
     61 
     62 	mv	a1, s2			# relocbase
     63 	addi	a0, sp, 2 * PTRSZ	# sp
     64 	call	_C_LABEL(_rtld)		# a0 = _rtld(sp, relocbase)
     65 	mv	t0, a0
     66 
     67 	PTR_L	a0, 2 * PTRSZ(sp)	# cleanup function
     68 //	PTR_L	a1, 3 * PTRSZ(sp)	# obj_main pointer (not used)
     69 	mv	a1, s1			# restore ps_strings
     70 	mv	sp, s0			# restore stack pointer
     71 	mv	s0, zero		# break stack chain
     72 	jr	t0			# _start(cleanup, ps_strings);
     73 END(_rtld_start)
     74 
     75 /*
     76  * Needs to be 12 so that stack alignment is preserved on both RV32 and RV64.
     77  */
     78 
     79 #define	XCALLFRAME_SIZ		(12 * SZREG)
     80 #define	XCALLFRAME_RA		( 8 * SZREG)
     81 #define	XCALLFRAME_A7		( 7 * SZREG)
     82 #define	XCALLFRAME_A6		( 6 * SZREG)
     83 #define	XCALLFRAME_A5		( 5 * SZREG)
     84 #define	XCALLFRAME_A4		( 4 * SZREG)
     85 #define	XCALLFRAME_A3		( 3 * SZREG)
     86 #define	XCALLFRAME_A2		( 2 * SZREG)
     87 #define	XCALLFRAME_A1		( 1 * SZREG)
     88 #define	XCALLFRAME_A0		( 0 * SZREG)
     89 
     90 /*
     91  * t0 = obj pointer
     92  * t1 = reloc offset
     93  */
     94 ENTRY_NP(_rtld_bind_start)
     95 	addi	sp, sp, -XCALLFRAME_SIZ	// save arguments on stack
     96 	REG_S	a0,  XCALLFRAME_A0(sp)
     97 	REG_S	a1,  XCALLFRAME_A1(sp)
     98 	REG_S	a2,  XCALLFRAME_A2(sp)
     99 	REG_S	a3,  XCALLFRAME_A3(sp)
    100 	REG_S	a4,  XCALLFRAME_A4(sp)
    101 	REG_S	a5,  XCALLFRAME_A5(sp)
    102 	REG_S	a6,  XCALLFRAME_A6(sp)
    103 	REG_S	a7,  XCALLFRAME_A7(sp)
    104 	REG_S	ra,  XCALLFRAME_RA(sp)
    105 
    106 	mv	a0, t0			/* object from got.plt[1] */
    107 	mv	a1, t1			/* reloc offset */
    108 
    109 	call	_C_LABEL(_rtld_bind)
    110 	mv	t0, a0			/* save function pointer */
    111 
    112 	REG_L	a0, XCALLFRAME_A0(sp)
    113 	REG_L	a1, XCALLFRAME_A1(sp)
    114 	REG_L	a2, XCALLFRAME_A2(sp)
    115 	REG_L	a3, XCALLFRAME_A3(sp)
    116 	REG_L	a4, XCALLFRAME_A4(sp)
    117 	REG_L	a5, XCALLFRAME_A5(sp)
    118 	REG_L	a6, XCALLFRAME_A6(sp)
    119 	REG_L	a7, XCALLFRAME_A7(sp)
    120 	REG_L	ra, XCALLFRAME_RA(sp)
    121 	addi	sp, sp, XCALLFRAME_SIZ
    122 	jr	t0
    123 END(_rtld_bind_start)
    124