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/* $OpenBSD: ldasm.S,v 1.10 2003/02/02 16:57:58 deraadt Exp $ */
/*
* Copyright (c) 1999 Dale Rahn
*
* 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed under OpenBSD by
* Dale Rahn.
* 4. 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.
*
*/
/*
* #ifdef blrl_never_causes_illegal_access
* background for the else of this define
* On the machine this code is being written, on a large portion
* of the tims this code is executed the blrl instruct causes an
* illegal instruction, hopefully by touching the page with a load
* will prevent the execute access from faulting.
*/
#define AUX_entry 9
#include <machine/asm.h>
#include <sys/syscall.h>
ENTRY(_dl_start)
mr 19, 1
stwu 1, (-16 -((AUX_entry+3)*4))(1) # Some space.
mflr 27 /* save off old link register */
stw 27, 4(19) /* save in normal location */
# squirrel away the arguments for main
mr 20, 3 #argc
mr 21, 4 #argv
mr 22, 5 #envp
mr 23, 6 # ???
.local .L___offset_sym
.type .L___offset_sym,@function
bl 1f
.L___offset_sym:
# this instruction never gets executed but can be used
# to find the virtual address where the page is loaded.
bl _GLOBAL_OFFSET_TABLE_@local-4
1:
mflr 5 # this stores where we are (+4)
lwz 18, 0(5) # load the instruction at offset_sym
# it contains an offset to the location
# of the GOT.
rlwinm 18,18,0,8,30 # mask off the offset portion of the instr.
/*
* these adds effectively calculate the value the
* bl _GLOBAL_OFFSET_TABLE_@local-4
* operation that would be below would calulate.
*/
add 28, 18, 5
mr 6, 5 # save offset for later use
/* mprotect GOT-4 for correct execution of blrl instruction */
li 0, SYS_mprotect
mr 3, 28
li 4, 4
li 5, 7 /* (PROT_READ|PROT_WRITE|PROT_EXEC) */
sc
mr 5, 6
li 0, 0
dcbf 5, 18
sync
isync
icbi 5, 18 # make certain that the got table addr is
# not in the icache
sync
isync
# calculate where we want to be (via the got)
bl _GLOBAL_OFFSET_TABLE_@local-4
mflr 28
lwz 4, .L___offset_sym@got(28)
mr 6, 4 # make copy of register for debugging
sub 4, 5, 4 # calculate offset (arg1 for _dl_boot)
mr 17, 4
subi 3, 21, 4 # Get stack pointer (arg0 for _dl_boot).
addi 4, 1, 8 # dl_data
bl _dl_boot_bind@local
mr 3, 21 # argv
mr 4, 22 # envp
mr 5, 17 # loff
addi 6, 1, 8 # dl_data
bl _dl_boot@local
mtctr 3 # put return value into ctr to execute
# get back the squirreled away the arguments for main
mr 3, 20
mr 4, 21
mr 5, 22
mr 6, 23
mtlr 27
lwz 1, 0(1) # Restore stack pointer.
bctr # Go execute the 'real' program.
ENTRY(_dl_bind_start)
stwu 1,-64(1)
stw 0,8(1) # save r0 - cerror ;-)
mflr 0
stw 0,68(1) # save lr
stw 3,12(1) # save r3-r10, C calling convention
stw 4,20(1) # r13 - r31 are preserved by called code
stw 5,24(1)
stw 6,28(1)
stw 7,32(1)
stw 8,36(1)
stw 9,40(1)
stw 10,44(1)
mr 3,12 # obj
mr 4,11 # reloff
bl _dl_bind@plt # _rtld_bind(obj, reloff)
mtctr 3
lwz 3,12(1)
lwz 4,20(1)
lwz 5,24(1)
lwz 6,28(1)
lwz 7,32(1)
lwz 8,36(1)
lwz 9,40(1)
lwz 10,44(1)
lwz 0,68(1) # restore lr
mtlr 0
lwz 0,8(1)
addi 1,1,64
bctr
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