1 /* $NetBSD: rtld_start.S,v 1.4 2001/09/26 04:06:43 mycroft Exp $ */
4 * Copyright (C) 1998 Tsubai Masanari
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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.
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
27 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 #include <machine/asm.h>
33 #include <machine/spr.h> /* For SPR_SPEFSCR if needed. */
35 .extern _GLOBAL_OFFSET_TABLE_
39 stwu %r1,-48(%r1) /* 16-byte aligned stack for reg saves +
40 exit_proc & obj _rtld args +
41 backchain & lrsave stack frame */
42 stw %r3,16(%r1) /* argc */
43 stw %r4,20(%r1) /* argv */
44 stw %r5,24(%r1) /* envp */
45 /* stw %r6,28(%r1) *//* obj (always 0) */
46 /* stw %r7,32(%r1) *//* cleanup (always 0) */
47 stw %r8,36(%r1) /* ps_strings */
50 * Perform initial relocation of ld-elf.so. Not as easy as it
52 * - perform small forward branch to put PC into link reg
53 * - use link-time constants to determine offset to the
54 * _DYNAMIC section and the GOT. Add these to the PC to
55 * convert to absolute addresses.
56 * - read GOT[0], which is the SVR4 ABI-specified link-time
57 * value of _DYNAMIC. Subtract this value from the absolute
58 * value to determine the load address
59 * - call reloc_non_plt_self() to fix up ld-elf.so's relocations
63 mr %r3,%r30 # save for _DYNAMIC
64 addis %r30,%r30,_GLOBAL_OFFSET_TABLE_-1b@ha
65 addi %r30,%r30,_GLOBAL_OFFSET_TABLE_-1b@l
66 addis %r3,%r3,_DYNAMIC-1b@ha # get _DYNAMIC actual address
67 addi %r3,%r3,_DYNAMIC-1b@l
68 lwz %r28,0(%r30) # get base-relative &_DYNAMIC
69 sub %r28,%r3,%r28 # r28 = relocbase
70 mr %r4,%r28 # r4 = relocbase
71 bl reloc_non_plt_self /* reloc_non_plt_self(&_DYNAMIC,base) */
74 * The _rtld() function likes to see a stack layout containing
75 * { argc, argv[0], argv[1] ... argv[N], 0, env[0], ... , env[N] }
76 * Since the PowerPC stack was 16-byte aligned at exec time, the
77 * original stack layout has to be found by moving back a word
78 * from the argv pointer.
80 lwz %r4,20(%r1) /* restore argv */
81 addi %r3,%r4,-4 /* locate argc ptr, &argv[-1] */
83 addi %r4,%r1,8 /* &exit_proc on stack */
84 addi %r5,%r1,12 /* &obj_main on stack */
86 bl _rtld /* &_start = _rtld(sp, &exit_proc, &obj_main)*/
90 * Restore args, with new obj/exit proc
92 lwz %r3,16(%r1) /* argc */
93 lwz %r4,20(%r1) /* argv */
94 lwz %r5,24(%r1) /* envp */
95 lwz %r6,12(%r1) /* obj */
96 lwz %r7,8(%r1) /* exit proc */
97 lwz %r8,36(%r1) /* ps_strings */
98 addi %r1,%r1,48 /* restore original stackptr */
100 blrl /* _start(argc, argv, envp, obj, cleanup, ps_strings) */
102 li %r0,1 /* _exit() */
106 /* stack space for 30 GPRs + SPEFSCR/ACC/lr/cr */
109 #define FUDGE 4 /* Fudge factor for alignment */
111 /* stack space for 30 GPRs + lr/cr */
116 /* Stack frame needs the 12-byte ABI frame plus fudge factor. */
117 #define STACK_SIZE (NREGS * GPRWIDTH + 4 * 2 + 12 + FUDGE)
120 * _rtld_bind_secureplt_start()
122 * Call into the MI binder (Secure-PLT stub).
123 * secure-plt expects %r11 to be the offset to the rela entry.
124 * bss-plt expects %r11 to be index of the rela entry.
125 * So for bss-plt, we multiply the index by 12 to get the offset.
127 _ENTRY(_rtld_bind_secureplt_start)
128 stwu %r1,-STACK_SIZE(%r1)
132 stw %r0,20(%r1) # save r0
136 * Instead of division which is costly we will use multiplicative
137 * inverse. a / n = ((a * inv(n)) >> 32)
138 * where inv(n) = (0x100000000 + n - 1) / n
141 lis %r11,0x15555556@h # load multiplicative inverse of 12
142 ori %r11,%r11,0x15555556@l
143 mulhwu %r11,%r11,%r0 # get high half of multiplication
149 * Call into the MI binder. This routine is reached via the PLT call cell,
150 * and then _rtld_powerpc_pltresolve().
151 * On entry, %r11 contains the index of the PLT cell, and %r12 contains
152 * a pointer to the ELF object for the file.
153 * Save all registers, call into the binder to resolve and fixup the external
154 * routine, and then transfer to the external routine on return.
158 _ENTRY(_rtld_bind_start)
159 stwu %r1,-STACK_SIZE(%r1)
163 stw %r0,20(%r1) # save r0
167 stw %r0,16(%r1) # save lr
169 stw %r0,12(%r1) # save cr
180 evstdd %r12, 104(%r1)
181 evstdd %r13, 112(%r1)
182 evstdd %r14, 120(%r1)
183 evstdd %r15, 128(%r1)
184 evstdd %r16, 136(%r1)
185 evstdd %r17, 144(%r1)
186 evstdd %r18, 152(%r1)
187 evstdd %r19, 160(%r1)
188 evstdd %r20, 168(%r1)
189 evstdd %r21, 176(%r1)
190 evstdd %r22, 184(%r1)
191 evstdd %r23, 192(%r1)
192 evstdd %r24, 200(%r1)
193 evstdd %r25, 208(%r1)
194 evstdd %r26, 216(%r1)
195 evstdd %r27, 224(%r1)
196 evstdd %r28, 232(%r1)
197 evstdd %r29, 240(%r1)
198 evstdd %r30, 248(%r1)
200 evstddx %r31, %r1, %r3
203 evmwumiaa %r0, %r0, %r0
204 evstddx %r0, %r1, %r3
205 mfspr %r3, SPR_SPEFSCR
208 stmw %r3,24(%r1) # save r3-r31
212 mulli %r4,%r11,12 # rela index * sizeof(Elf_Rela)
213 bl _rtld_bind # target addr = _rtld_bind(obj, reloff)
214 mtctr %r3 # move absolute target addr into ctr
218 mtspr SPR_SPEFSCR, %r3
251 evlddx %r31, %r1, %r0
253 lmw %r3,24(%r1) # restore r3-r31
255 lwz %r0,12(%r1) # restore cr
257 lwz %r0,16(%r1) # restore lr
262 lwz %r0,20(%r1) # restore r0
265 addi %r1,%r1,STACK_SIZE # restore stack
266 bctr # jump to target
270 * _rtld_powerpc_pltresolve()
272 * This routine is copied into the latter part of the 72-byte reserved
273 * area at the start of the PLT. The absolute address of the _rtld_bind_start
274 * routine, and the ELF object for the loaded file, are inserted into
275 * the code by the reloc.c:init_pltgot() routine.
276 * The first time an external routine is called, the PLT slot will
277 * set up %r11 to the offset of the slot, and will jump to this routine.
278 * The ELF object is shifted into %r11, and _rtld_bind_start is called
279 * to complete the binding.
281 _ENTRY(_rtld_powerpc_pltlongresolve)
282 lis %r12,0 # lis 12,jmptab@ha
283 addi %r12,%r12,0 # addi 12,12,jmptab@l
284 subf %r11,%r12,%r11 # reloff
286 srw %r11,%r11,%r12 # index = reloff/sizeof(Elf_Addr)
287 _ENTRY(_rtld_powerpc_pltresolve)
288 lis %r12,0 # lis 12,_rtld_bind_start@ha
289 addi %r12,%r12,0 # addi 12,12,_rtld_bind_start@l
291 lis %r12,0 # lis 12,obj@ha
292 addi %r12,%r12,0 # addi 12,12,obj@l
296 * _rtld_powerpc_pltcall()
298 * This routine is copied into the 72-byte reserved area at the
299 * start of the PLT. The reloc.c:init_pltgot() routine inserts
300 * the absolute address of the jumptable.
301 * Control is transferred to this routine when the binder has
302 * located the external routine, but determined that it is > 32Mb
303 * from the PLT slot. Code is inserted into the PLT slot to set up
304 * %r11 with the jumptable index, and jump to here, where the
305 * absolute address of the external routine is loaded from the
306 * jumptable and transferred to
308 _ENTRY(_rtld_powerpc_pltcall)
309 slwi %r11,%r11,2 # jmptab offset = index * 4
310 addis %r11,%r11,0 # addis 11,11,jmptab@ha
311 lwz %r11,0(%r11) # lwz 11,jmptab@l(11)
313 bctr # (*jmptab[index])()
315 .section .note.GNU-stack,"",%progbits