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/* $NetBSD: rtld_start.S,v 1.4 2001/09/26 04:06:43 mycroft Exp $ */
/*-
* Copyright (C) 1998 Tsubai Masanari
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $FreeBSD$
*/
#include <machine/asm.h>
.extern _GLOBAL_OFFSET_TABLE_
.extern _DYNAMIC
_ENTRY(.rtld_start)
stwu %r1,-48(%r1) /* 16-byte aligned stack for reg saves +
exit_proc & obj _rtld args +
backchain & lrsave stack frame */
stw %r3,16(%r1) /* argc */
stw %r4,20(%r1) /* argv */
stw %r5,24(%r1) /* envp */
/* stw %r6,28(%r1) *//* obj (always 0) */
/* stw %r7,32(%r1) *//* cleanup (always 0) */
stw %r8,36(%r1) /* ps_strings */
/*
* Perform initial relocation of ld-elf.so. Not as easy as it
* sounds.
* - perform small forward branch to put PC into link reg
* - use link-time constants to determine offset to the
* _DYNAMIC section and the GOT. Add these to the PC to
* convert to absolute addresses.
* - sync icache to allow execution of the SVR4 ABI-specified
* blrl instruction preceding the GOT
* - Use this instruction to determine the GOT absolute address
* - read GOT[0], which is the SVR4 ABI-specified link-time
* value of _DYNAMIC. Subtract this value from the absolute
* value to determine the load address
* - call reloc_non_plt_self() to fix up ld-elf.so's relocations
*/
bl 1f
.long _DYNAMIC-.
.long _GLOBAL_OFFSET_TABLE_-. /* branch lr + 4 */
1:
mflr %r3 /* PC value at .long */
lwz %r4,4(%r3)
add %r4,%r4,%r3 /* &_GLOBAL_OFFSET_TABLE-4, blrl insn. */
dcbst %r0,%r4 /* sync i-cache with d-cache */
sync
icbi %r0,%r4
isync
lwz %r4,0(%r3) /* offset to _DYNAMIC */
add %r3,%r4,%r3 /* r3 = &_DYNAMIC, absolute value */
bl _GLOBAL_OFFSET_TABLE_@local-4
mflr %r4 /* &_GLOBAL_OFFSET_TABLE_, absolute value */
lwz %r4,0(%r4) /* linker &_DYNAMIC, from got[0] */
subf %r4,%r4,%r3 /* subtract to calculate relocbase */
bl reloc_non_plt_self@plt /* reloc_non_plt_self(&_DYNAMIC,base) */
/*
* The _rtld() function likes to see a stack layout containing
* { argc, argv[0], argv[1] ... argv[N], 0, env[0], ... , env[N] }
* Since the PowerPC stack was 16-byte aligned at exec time, the
* original stack layout has to be found by moving back a word
* from the argv pointer.
*/
lwz %r4,20(%r1) /* restore argv */
addi %r3,%r4,-4 /* locate argc ptr, &argv[-1] */
addi %r4,%r1,8 /* &exit_proc on stack */
addi %r5,%r1,12 /* &obj_main on stack */
bl _rtld@plt /* &_start = _rtld(sp, &exit_proc, &obj_main)*/
mtlr %r3
/*
* Restore args, with new obj/exit proc
*/
lwz %r3,16(%r1) /* argc */
lwz %r4,20(%r1) /* argv */
lwz %r5,24(%r1) /* envp */
lwz %r6,12(%r1) /* obj */
lwz %r7,8(%r1) /* exit proc */
lwz %r8,36(%r1) /* ps_strings */
addi %r1,%r1,48 /* restore original stackptr */
blrl /* _start(argc, argv, envp, obj, cleanup, ps_strings) */
li %r0,1 /* _exit() */
sc
/*
* _rtld_bind_start()
*
* Call into the MI binder. This routine is reached via the PLT call cell,
* and then _rtld_powerpc_pltresolve().
* On entry, %r11 contains the index of the PLT cell, and %r12 contains
* a pointer to the ELF object for the file.
* Save all registers, call into the binder to resolve and fixup the external
* routine, and then transfer to the external routine on return.
*/
.globl _rtld_bind
_ENTRY(_rtld_bind_start)
stwu %r1,-160(%r1) # stack space for 29 regs + r0/lr/cr
stw %r0,20(%r1) # save r0
mflr %r0
stw %r0,16(%r1) # save lr
mfcr %r0
stw %r0,12(%r1) # save cr
stmw %r3,24(%r1) # save r3-r31
mr %r3,%r12 # obj
mulli %r4,%r11,12 # rela index * sizeof(Elf_Rela)
bl _rtld_bind@PLT # target addr = _rtld_bind(obj, reloff)
mtctr %r3 # move absolute target addr into ctr
lmw %r3,24(%r1) # restore r3-r31
lwz %r0,12(%r1) # restore cr
mtcr %r0
lwz %r0,16(%r1) # restore lr
mtlr %r0
lwz %r0,20(%r1) # restore r0
addi %r1,%r1,160 # restore stack
bctr # jump to target
/*
* _rtld_powerpc_pltresolve()
*
* This routine is copied into the latter part of the 72-byte reserved
* area at the start of the PLT. The absolute address of the _rtld_bind_start
* routine, and the ELF object for the loaded file, are inserted into
* the code by the reloc.c:init_pltgot() routine.
* The first time an external routine is called, the PLT slot will
* set up %r11 to the offset of the slot, and will jump to this routine.
* The ELF object is shifted into %r11, and _rtld_bind_start is called
* to complete the binding.
*/
_ENTRY(_rtld_powerpc_pltresolve)
lis %r12,0 # lis 12,_rtld_bind_start@ha
addi %r12,%r12,0 # addi 12,12,_rtld_bind_start@l
mtctr %r12
lis %r12,0 # lis 12,obj@ha
addi %r12,%r12,0 # addi 12,12,obj@l
bctr
/*
* _rtld_powerpc_pltcall()
*
* This routine is copied into the 72-byte reserved area at the
* start of the PLT. The reloc.c:init_pltgot() routine inserts
* the absolute address of the jumptable.
* Control is transferred to this routine when the binder has
* located the external routine, but determined that it is > 32Mb
* from the PLT slot. Code is inserted into the PLT slot to set up
* %r11 with the jumptable index, and jump to here, where the
* absolute address of the external routine is loaded from the
* jumptable and transferred to
*/
_ENTRY(_rtld_powerpc_pltcall)
slwi %r11,%r11,2 # jmptab offset = index * 4
addis %r11,%r11,0 # addis 11,11,jmptab@ha
lwz %r11,0(%r11) # lwz 11,jmptab@l(11)
mtctr %r11
bctr # (*jmptab[index])()
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