/* $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. */ #include <machine/asm.h> #include <machine/spr.h> /* For SPR_SPEFSCR if needed. */ .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. * - 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 */ bcl 20,31,1f 1: mflr %r30 mr %r3,%r30 # save for _DYNAMIC addis %r30,%r30,_GLOBAL_OFFSET_TABLE_-1b@ha addi %r30,%r30,_GLOBAL_OFFSET_TABLE_-1b@l addis %r3,%r3,_DYNAMIC-1b@ha # get _DYNAMIC actual address addi %r3,%r3,_DYNAMIC-1b@l lwz %r28,0(%r30) # get base-relative &_DYNAMIC sub %r28,%r3,%r28 # r28 = relocbase mr %r4,%r28 # r4 = relocbase bl reloc_non_plt_self /* 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 /* &_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 _END(.rtld_start) /* stack space for 30 GPRs + lr/cr */ #define NREGS 30 #define GPRWIDTH 4 #define FUDGE 4 /* Stack frame needs the 12-byte ABI frame plus fudge factor. */ #define STACK_SIZE (NREGS * GPRWIDTH + 4 * 2 + 12 + FUDGE) /* * _rtld_bind_secureplt_start() * * Call into the MI binder (Secure-PLT stub). * secure-plt expects %r11 to be the offset to the rela entry. * bss-plt expects %r11 to be index of the rela entry. * So for bss-plt, we multiply the index by 12 to get the offset. */ _ENTRY(_rtld_bind_secureplt_start) stwu %r1,-STACK_SIZE(%r1) stw %r0,20(%r1) # save r0 /* * Instead of division which is costly we will use multiplicative * inverse. a / n = ((a * inv(n)) >> 32) * where inv(n) = (0x100000000 + n - 1) / n */ mr %r0,%r11 lis %r11,0x15555556@h # load multiplicative inverse of 12 ori %r11,%r11,0x15555556@l mulhwu %r11,%r11,%r0 # get high half of multiplication b 1f _END(_rtld_bind_secureplt_start) /* * _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,-STACK_SIZE(%r1) stw %r0,20(%r1) # save r0 1: 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 # 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,STACK_SIZE # restore stack bctr # jump to target _END(_rtld_bind_start) /* * _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_pltlongresolve) lis %r12,0 # lis 12,jmptab@ha addi %r12,%r12,0 # addi 12,12,jmptab@l subf %r11,%r12,%r11 # reloff li %r12,2 srw %r11,%r11,%r12 # index = reloff/sizeof(Elf_Addr) _END(_rtld_powerpc_pltlongresolve) _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 _END(_rtld_powerpc_pltresolve) /* * _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])() _END(_rtld_powerpc_pltcall) .section .note.GNU-stack,"",%progbits
