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glibc/sysdeps/unix/sysv/linux/i386/pointer_guard.h

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Introduce <pointer_guard.h>, extracted from <sysdep.h> This allows us to define a generic no-op version of PTR_MANGLE and PTR_DEMANGLE. In the future, we can use PTR_MANGLE and PTR_DEMANGLE unconditionally in C sources, avoiding an unintended loss of hardening due to missing include files or unlucky header inclusion ordering. In i386 and x86_64, we can avoid a <tls.h> dependency in the C code by using the computed constant from <tcb-offsets.h>. <sysdep.h> no longer includes these definitions, so there is no cyclic dependency anymore when computing the <tcb-offsets.h> constants. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2022-10-18 15:00:07 +00:00
/* Pointer obfuscation implenentation. i386 version.
Update copyright dates with scripts/update-copyrights
2023-01-06 21:08:04 +00:00
Copyright (C) 2005-2023 Free Software Foundation, Inc.
Introduce <pointer_guard.h>, extracted from <sysdep.h> This allows us to define a generic no-op version of PTR_MANGLE and PTR_DEMANGLE. In the future, we can use PTR_MANGLE and PTR_DEMANGLE unconditionally in C sources, avoiding an unintended loss of hardening due to missing include files or unlucky header inclusion ordering. In i386 and x86_64, we can avoid a <tls.h> dependency in the C code by using the computed constant from <tcb-offsets.h>. <sysdep.h> no longer includes these definitions, so there is no cyclic dependency anymore when computing the <tcb-offsets.h> constants. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2022-10-18 15:00:07 +00:00
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef POINTER_GUARD_H
#define POINTER_GUARD_H
#include <tcb-offsets.h>
#if IS_IN (rtld)
/* We cannot use the thread descriptor because in ld.so we use setjmp
earlier than the descriptor is initialized. Using a global variable
is too complicated here since we have no PC-relative addressing mode. */
# include <sysdeps/generic/pointer_guard.h>
#else
# ifdef __ASSEMBLER__
# define PTR_MANGLE(reg) xorl %gs:POINTER_GUARD, reg; \
roll $9, reg
# define PTR_DEMANGLE(reg) rorl $9, reg; \
xorl %gs:POINTER_GUARD, reg
# else
# define PTR_MANGLE(var) asm ("xorl %%gs:%c2, %0\n" \
"roll $9, %0" \
: "=r" (var) \
: "0" (var), \
"i" (POINTER_GUARD))
# define PTR_DEMANGLE(var) asm ("rorl $9, %0\n" \
"xorl %%gs:%c2, %0" \
: "=r" (var) \
: "0" (var), \
"i" (POINTER_GUARD))
# endif
#endif
#endif /* POINTER_GUARD_H */
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