xref: /netbsd-src/libexec/ld.elf_so/arch/riscv/rtld_start.S (revision 75b842b84762e0251223b719bf77fbef2e651bf6)
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
47ENTRY(_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);
73END(_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 */
94ENTRY_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
123END(_rtld_bind_start)
124