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035c012e32
It turns out the startup code in csu/elf-init.c has a perfect pair of ROP gadgets (see Marco-Gisbert and Ripoll-Ripoll, "return-to-csu: A New Method to Bypass 64-bit Linux ASLR"). These functions are not needed in dynamically-linked binaries because DT_INIT/DT_INIT_ARRAY are already processed by the dynamic linker. However, the dynamic linker skipped the main program for some reason. For maximum backwards compatibility, this is not changed, and instead, the main map is consulted from __libc_start_main if the init function argument is a NULL pointer. For statically linked binaries, the old approach based on linker symbols is still used because there is nothing else available. A new symbol version __libc_start_main@@GLIBC_2.34 is introduced because new binaries running on an old libc would not run their ELF constructors, leading to difficult-to-debug issues.
135 lines
3.8 KiB
ArmAsm
135 lines
3.8 KiB
ArmAsm
/* ELF startup code for HPPA.
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Copyright (C) 2002-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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In addition to the permissions in the GNU Lesser General Public
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License, the Free Software Foundation gives you unlimited
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permission to link the compiled version of this file with other
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programs, and to distribute those programs without any restriction
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coming from the use of this file. (The GNU Lesser General Public
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License restrictions do apply in other respects; for example, they
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cover modification of the file, and distribution when not linked
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into another program.)
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Note that people who make modified versions of this file are not
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obligated to grant this special exception for their modified
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versions; it is their choice whether to do so. The GNU Lesser
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General Public License gives permission to release a modified
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version without this exception; this exception also makes it
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possible to release a modified version which carries forward this
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exception.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library. If not, see
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<https://www.gnu.org/licenses/>. */
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.import main, code
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.import $global$, data
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.import __libc_start_main, code
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/* Have the linker create plabel words so we get PLABEL32
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relocs and not 21/14. The use of 21/14 relocs is only
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supported in the latest dynamic linker. */
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#ifdef PIC
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.section .data.rel.ro,"aw",@progbits
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#else
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.section .rodata,"a",@progbits
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#endif
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.align 4
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.Lpmain:
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.word P%main
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.Lp__libc_start_main:
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.word P%__libc_start_main
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.text
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.align 4
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.globl _start
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.export _start, ENTRY
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.type _start,@function
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_start:
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/* At entry to the function we have:
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r26 - Unused
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r25 - argc
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r24 - argv
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r23 - False _dl_fini plabel address
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This function is called from the lower half of RTLD_START.
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The call to __libc_start_main expects:
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1. r26 - Application main
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2. r25 - argc
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3. r24 - argv
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4. r23 - init (unused)
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5. sp-52 - fini (unused)
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6. sp-56 - rtld_fini
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7. sp-60 - stackend */
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.proc
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.callinfo
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/* Clear previous-sp. */
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stw %r0, -4(%sp)
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/* Setup the stack and frame. */
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stw %rp, -20(%sp)
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ldo 64(%sp), %sp
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stw %sp, -4(%sp)
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stw %r19, -32(%sp)
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/* argc and argv should be in 25 and 24 (2nd and 3rd argument) */
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/* void (*rtld_fini) (void) (6th argument) */
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stw %r23, -56(%sp)
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/* Need to setup 1, 4, 5, and 7th arguments */
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#ifdef PIC
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/* Load $global$ address into %dp */
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bl .+8, %dp
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addil L'$global$-$PIC_pcrel$0+1, %dp
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ldo R'$global$-$PIC_pcrel$0+5(%r1), %dp
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/* load main (1st argument) */
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addil LT'.Lpmain, %r19
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ldw RT'.Lpmain(%r1), %r26
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ldw 0(%r26),%r26
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#else
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/* Load $global$ address into %dp */
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ldil L%$global$, %dp
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ldo R%$global$(%dp), %dp
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/* load main (1st argument) */
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ldil LR'.Lpmain, %r26
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ldw RR'.Lpmain(%r26), %r26
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#endif
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ldi 0,%r23 /* Used to be init. */
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ldi 0,%r22 /* Used to be fini. */
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/* Store 5th argument */
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stw %r22, -52(%sp)
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/* void *stack_end (7th argument) */
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stw %sp, -60(%sp)
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bl __libc_start_main,%r2
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nop
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/* die horribly if it returned (it shouldn't) */
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iitlbp %r0,(%sr0,%r0)
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nop
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.procend
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/* Define a symbol for the first piece of initialized data. */
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.data
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.globl __data_start
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__data_start:
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.long 0
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.weak data_start
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data_start = __data_start
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