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6cd380dd36
eXecute-Only Memory (XOM) is a protection mechanism against some ROP attacks. XOM sets the code as executable and unreadable, so the access to any data, like literal pools, in the code section causes the fault with XOM. The compiler can disable literal pools for C source files, but not for assembly files, so I use movz/movk instead of literal pools in start.S for XOM. I add MOVL macro with movz/movk instructions like movl pseudo-instruction in armasm, and use the macro instead of literal pools. * sysdeps/aarch64/start.S: Use MOVL instead of literal pools. * sysdeps/aarch64/sysdep.h (MOVL): Add MOVL macro.
95 lines
2.5 KiB
ArmAsm
95 lines
2.5 KiB
ArmAsm
/* Copyright (C) 1995-2017 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 License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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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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<http://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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/* This is the canonical entry point, usually the first thing in the text
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segment.
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Note that the code in the .init section has already been run.
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This includes _init and _libc_init
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At this entry point, most registers' values are unspecified, except:
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x0/w0 Contains a function pointer to be registered with `atexit'.
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This is how the dynamic linker arranges to have DT_FINI
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functions called for shared libraries that have been loaded
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before this code runs.
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sp The stack contains the arguments and environment:
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0(sp) argc
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8(sp) argv[0]
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...
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(8*argc)(sp) NULL
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(8*(argc+1))(sp) envp[0]
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...
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NULL
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*/
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.text
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.globl _start
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.type _start,#function
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_start:
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/* Create an initial frame with 0 LR and FP */
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mov x29, #0
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mov x30, #0
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/* Setup rtld_fini in argument register */
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mov x5, x0
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/* Load argc and a pointer to argv */
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ldr PTR_REG (1), [sp, #0]
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add x2, sp, #PTR_SIZE
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/* Setup stack limit in argument register */
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mov x6, sp
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#ifdef SHARED
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adrp x0, :got:main
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ldr PTR_REG (0), [x0, #:got_lo12:main]
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adrp x3, :got:__libc_csu_init
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ldr PTR_REG (3), [x3, #:got_lo12:__libc_csu_init]
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adrp x4, :got:__libc_csu_fini
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ldr PTR_REG (4), [x4, #:got_lo12:__libc_csu_fini]
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#else
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/* Set up the other arguments in registers */
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MOVL (0, main)
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MOVL (3, __libc_csu_init)
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MOVL (4, __libc_csu_fini)
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#endif
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/* __libc_start_main (main, argc, argv, init, fini, rtld_fini,
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stack_end) */
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/* Let the libc call main and exit with its return code. */
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bl __libc_start_main
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/* should never get here....*/
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bl abort
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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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