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bb019bc68f
Use __seg_gs named address space qualifiers in PTR_MANGLE() and PTR_DEMANGLE() macros to access the pointer_guard field in the TCB. This change allows the compiler to eliminate redundant reads of the variable, reducing the number of reads from 105 to 94 and decreasing the text size of the library by 280 bytes. While at it, fix a few trivial whitespace issues as well Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
53 lines
1.9 KiB
C
53 lines
1.9 KiB
C
/* Pointer obfuscation implenentation. i386 version.
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Copyright (C) 2005-2025 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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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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#ifndef POINTER_GUARD_H
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#define POINTER_GUARD_H
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#include <tcb-offsets.h>
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#if IS_IN (rtld)
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/* We cannot use the thread descriptor because in ld.so we use setjmp
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earlier than the descriptor is initialized. Using a global variable
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is too complicated here since we have no PC-relative addressing mode. */
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# include <sysdeps/generic/pointer_guard.h>
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#else
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# ifdef __ASSEMBLER__
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# define PTR_MANGLE(reg) xorl %gs:POINTER_GUARD, reg; \
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roll $9, reg
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# define PTR_DEMANGLE(reg) rorl $9, reg; \
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xorl %gs:POINTER_GUARD, reg
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# else
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# include <tls.h>
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# define PTR_MANGLE(var) do \
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{ \
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(var) = (__typeof (var)) ((uintptr_t) (var) \
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^ ((tcbhead_t __seg_gs *)0)->pointer_guard); \
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asm ("roll $9, %0" : "+r" (var)); \
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} while (0)
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# define PTR_DEMANGLE(var) do \
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{ \
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asm ("rorl $9, %0" : "+r" (var)); \
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(var) = (__typeof (var)) ((uintptr_t) (var) \
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^ ((tcbhead_t __seg_gs *)0)->pointer_guard); \
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} while (0)
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# endif
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#endif
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#endif /* POINTER_GUARD_H */
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