1 /* IFUNC generic definitions. 2 This file is part of the GNU C Library. 3 Copyright (C) 2017-2022 Free Software Foundation, Inc. 4 5 The GNU C Library is free software; you can redistribute it and/or 6 modify it under the terms of the GNU Lesser General Public 7 License as published by the Free Software Foundation; either 8 version 2.1 of the License, or (at your option) any later version. 9 10 The GNU C Library is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 Lesser General Public License for more details. 14 15 You should have received a copy of the GNU Lesser General Public 16 License along with the GNU C Library; if not, see 17 <https://www.gnu.org/licenses/>. */ 18 19 /* These macros are used to implement ifunc selection in C. To implement 20 an ifunc function, foo, which returns the address of __foo_impl1 or 21 __foo_impl2: 22 23 #define foo __redirect_foo 24 #include <foo.h> 25 #undef foo 26 #define SYMBOL_NAME foo 27 #include <ifunc-init.h> 28 29 extern __typeof (REDIRECT_NAME) OPTIMIZE (impl1) attribute_hidden; 30 extern __typeof (REDIRECT_NAME) OPTIMIZE (impl2) attribute_hidden; 31 32 static inline void * 33 foo_selector (void) 34 { 35 if (condition) 36 return OPTIMIZE (impl2); 37 38 return OPTIMIZE (impl1); 39 } 40 41 libc_ifunc_redirected (__redirect_foo, foo, IFUNC_SELECTOR ()); 42 */ 43 44 #define PASTER1(x,y) x##_##y 45 #define EVALUATOR1(x,y) PASTER1 (x,y) 46 #define PASTER2(x,y) __##x##_##y 47 #define EVALUATOR2(x,y) PASTER2 (x,y) 48 49 /* Basically set '__redirect_<symbol>' to use as type definition, 50 '__<symbol>_<variant>' as the optimized implementation and 51 '<symbol>_ifunc_selector' as the IFUNC selector. */ 52 #define REDIRECT_NAME EVALUATOR1 (__redirect, SYMBOL_NAME) 53 #define IFUNC_SELECTOR EVALUATOR1 (SYMBOL_NAME, ifunc_selector) 54 #define OPTIMIZE1(name) EVALUATOR1 (SYMBOL_NAME, name) 55 #define OPTIMIZE2(name) EVALUATOR2 (SYMBOL_NAME, name) 56 /* Default is to use OPTIMIZE2. */ 57 #define OPTIMIZE(name) OPTIMIZE2(name) 58