| 1 | /* Definition of __INDIRECT_RETURN. x86 version. |
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| 2 | Copyright (C) 2018-2022 Free Software Foundation, Inc. |
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| 3 | This file is part of the GNU C Library. |
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| 4 | |
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| 5 | The GNU C Library is free software; you can redistribute it and/or |
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| 6 | modify it under the terms of the GNU Lesser General Public |
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| 7 | License as published by the Free Software Foundation; either |
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| 8 | version 2.1 of the License, or (at your option) any later version. |
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| 9 | |
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| 10 | The GNU C Library is distributed in the hope that it will be useful, |
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 13 | Lesser General Public License for more details. |
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| 14 | |
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| 15 | You should have received a copy of the GNU Lesser General Public |
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| 16 | License along with the GNU C Library; if not, see |
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| 17 | <https://www.gnu.org/licenses/>. */ |
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| 18 | |
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| 19 | #ifndef _UCONTEXT_H |
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| 20 | # error "Never include <bits/indirect-return.h> directly; use <ucontext.h> instead." |
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| 21 | #endif |
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| 22 | |
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| 23 | /* On x86, swapcontext returns via indirect branch when the shadow stack |
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| 24 | is enabled. Define __INDIRECT_RETURN to indicate whether swapcontext |
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| 25 | returns via indirect branch. */ |
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| 26 | #if defined __CET__ && (__CET__ & 2) != 0 |
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| 27 | # if __glibc_has_attribute (__indirect_return__) |
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| 28 | # define __INDIRECT_RETURN __attribute__ ((__indirect_return__)) |
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| 29 | # else |
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| 30 | /* Newer compilers provide the indirect_return attribute, but without |
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| 31 | it we can use returns_twice to affect the optimizer in the same |
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| 32 | way and avoid unsafe optimizations. */ |
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| 33 | # define __INDIRECT_RETURN __attribute__ ((__returns_twice__)) |
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| 34 | # endif |
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| 35 | #else |
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| 36 | # define __INDIRECT_RETURN |
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| 37 | #endif |
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| 38 | |
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