rtld_start.S revision 1.13
1 /* $NetBSD: rtld_start.S,v 1.13 2002/09/26 02:14:10 mycroft Exp $ */ 2 3 /*- 4 * Copyright (c) 2000 Eduardo Horvath. 5 * Copyright (c) 1999, 2002 The NetBSD Foundation, Inc. 6 * All rights reserved. 7 * 8 * This code is derived from software contributed to The NetBSD Foundation 9 * by Christos Zoulas, Paul Kranenburg and by Charles M. Hannum. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the NetBSD 22 * Foundation, Inc. and its contributors. 23 * 4. Neither the name of The NetBSD Foundation nor the names of its 24 * contributors may be used to endorse or promote products derived 25 * from this software without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 37 * POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 #include <machine/asm.h> 41 #define _LOCORE 42 #include <machine/frame.h> 43 44 /* 45 * ELF: 46 * On startup the stack should contain 16 extended word register save area, 47 * followed by the arg count, etc. 48 * 49 * _rtld() expects the stack pointer to point to two longwords for argument 50 * return followed by argc, etc. We need to create a pointer to 51 * &argc + 16 and pass that in. The return args will be in those locations. 52 * 53 * NB: We are violating the ELF spec by passing a pointer to the ps strings in 54 * %g1 instead of a termination routine. 55 */ 56 57 .register %g2,#scratch 58 .register %g3,#scratch 59 60 /* Offset of ARGC from bottom of stack */ 61 #define ARGC 176 62 63 .section ".text" 64 .align 4 65 .LLGETPC0: 66 retl 67 add %o7,%l7,%l7 68 69 .section ".text" 70 .align 4 71 .global _rtld_start 72 .type _rtld_start,@function 73 _rtld_start: 74 mov 0, %fp /* Erect a fence post for ourselves */ 75 mov %g1, %l1 /* save ps_strings */ 76 sub %sp, 48+16, %sp /* Make room for return args */ 77 78 sethi %hi(_GLOBAL_OFFSET_TABLE_-4), %l7 79 call .LLGETPC0 80 add %l7, %lo(_GLOBAL_OFFSET_TABLE_+4), %l7 81 ldx [%l7+_DYNAMIC], %o0 82 ldx [%l7+_GLOBAL_OFFSET_TABLE_], %l0 83 84 sub %l7, %l0, %o1 /* relocbase */ 85 call _rtld_relocate_nonplt_self 86 add %o0, %o1, %o0 /* &_DYNAMIC */ 87 88 sub %l7, %l0, %o1 /* relocbase */ 89 call _rtld 90 add %sp, BIAS + ARGC, %o0 /* &argc - 16 */ 91 92 ldx [%sp + BIAS + ARGC], %g3 /* arg: cleanup */ 93 ldx [%sp + BIAS + ARGC + 8], %g2 /* arg: obj */ 94 add %sp, 48+16, %sp /* restore stack pointer */ 95 96 jmp %o0 97 mov %l1, %g1 /* restore ps_strings */ 98 99 100 /* 101 * We have two separate entry points to the runtime linker. 102 * I'm implementing this following the SPARC v9 ABI spec. 103 * 104 * _rtld_bind_start_0(x, y) is called from .PLT0, and is used for 105 * PLT entries above 32768. 106 * 107 * _rtld_bind_start_1(x, y) is called from .PLT1, and is used for 108 * PLT entries below 32768. 109 * 110 * The first two entries of PLT2 contain the xword object pointer. 111 * 112 * These routines are called with two longword arguments, 113 * x and y. To calculate the address of the entry, 114 * _rtld_bind_start_1(x, y) does: 115 * 116 * n = x >> 15; 117 * 118 * and _rtld_bind_start_0(x, y) does: 119 * 120 * i = x - y + 1048596; 121 * n = 32768 + (i/5120)*160 + (i%5120)/24; 122 * 123 * Neither routine needs to issue a save since it's already been 124 * done in the PLT entry. 125 */ 126 127 /* NOTE: _rtld_bind_start_0 is untested. Hence the debug stuff */ 128 129 .section ".text" 130 .align 4 131 .global _rtld_bind_start_0 132 .type _rtld_bind_start_0,@function 133 _rtld_bind_start_0: # (y, x) 134 #if 0 135 call _rtld_bind_start_0_stub 136 ldx [%o0 + (10*4)], %l7 137 mov %o0, %o1 138 139 call _rtld_bind 140 mov %l7, %o0 141 #else 142 /* %o0 = obj->pltgot[6] */ 143 /* %o1 = plt[4] */ 144 /* %o1 - %o0 + 8 == offset of plt[] from obj->pltgot[] */ 145 /* -32768*32 to get offset from beginning of upper PLT section */ 146 147 sethi %hi(32768*32-8), %l1 148 sub %o1, %o0, %l0 /* i = x - y */ 149 or %l1, %lo(32768*32-8), %l1 150 sub %l0, %l1, %l0 /* i = x - y + 8 - 32768*32 */ 151 152 ldx [%o0 + (10*4)], %o0 /* Load object pointer from PLT2 */ 153 154 sethi %hi(5120), %l1 155 sdivx %l0, %l1, %l1 /* Calculate i/5120 */ 156 sllx %l1, 2, %l2 157 add %l2, %l1, %l2 158 sllx %l2, 10, %l2 159 sub %l0, %l2, %l2 /* And i%5120 */ 160 161 /* Let the division churn for a bit. */ 162 sdivx %l2, 24, %l4 /* (i%5120)/24 */ 163 164 /* 160 is (32 * 5) or (32 * (4 + 1)) */ 165 sllx %l1, 2, %l3 /* 4 * (i/5120) */ 166 add %l1, %l3, %l3 /* 5 * (i/5120) */ 167 sllx %l3, 5, %l3 /* 32 * 5 * (i/5120) */ 168 169 sethi %hi(32768), %l6 170 add %l3, %l4, %l5 /* %l5 = (i/5120)*160 + (i%5120)/24; */ 171 172 call _rtld_bind /* Call _rtld_bind(obj, offset) */ 173 add %l5, %l6, %o1 /* %o1 = 32768 + ... */ 174 175 jmp %o0 /* return value == function address */ 176 restore /* Dump our stack frame */ 177 #endif 178 179 .section ".text" 180 .align 4 181 .global _rtld_bind_start_1 182 .type _rtld_bind_start_1,@function 183 _rtld_bind_start_1: # (y, x) 184 ldx [%o0 + (2*4)], %o0 /* Load object pointer from PLT2 */ 185 186 call _rtld_bind /* Call _rtld_bind(obj, offset) */ 187 srax %o1, 15, %o1 /* %o1 is the index to our PLT slot */ 188 189 jmp %o0 /* return value == function address */ 190 restore /* Dump our stack frame */ 191 192
Indexes created Tue Sep 30 20:09:53 GMT 2025