diff options
Diffstat (limited to 'REORG.TODO/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h')
-rw-r--r-- | REORG.TODO/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h b/REORG.TODO/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h new file mode 100644 index 0000000000..8d474d0d04 --- /dev/null +++ b/REORG.TODO/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h @@ -0,0 +1,44 @@ +/* Optional code to distinguish library flavours. x86-64 version. + Copyright (C) 2015-2017 Free Software Foundation, Inc. + 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 + <http://www.gnu.org/licenses/>. */ + +#ifndef _DL_LIBRECON_H + +#include <sysdeps/unix/sysv/linux/dl-librecon.h> + +/* Recognizing extra environment variables. For 64-bit applications, + branch prediction performance may be negatively impacted when the + target of a branch is more than 4GB away from the branch. Add the + Prefer_MAP_32BIT_EXEC bit so that mmap will try to map executable + pages with MAP_32BIT first. NB: MAP_32BIT will map to lower 2GB, + not lower 4GB, address. Prefer_MAP_32BIT_EXEC reduces bits available + for address space layout randomization (ASLR). Prefer_MAP_32BIT_EXEC + is always disabled for SUID programs and can be enabled by setting + environment variable, LD_PREFER_MAP_32BIT_EXEC. */ +#define EXTRA_LD_ENVVARS \ + case 21: \ + if (memcmp (envline, "PREFER_MAP_32BIT_EXEC", 21) == 0) \ + GLRO(dl_x86_cpu_features).feature[index_arch_Prefer_MAP_32BIT_EXEC] \ + |= bit_arch_Prefer_MAP_32BIT_EXEC; \ + break; + +/* Extra unsecure variables. The names are all stuffed in a single + string which means they have to be terminated with a '\0' explicitly. */ +#define EXTRA_UNSECURE_ENVVARS \ + "LD_PREFER_MAP_32BIT_EXEC\0" + +#endif /* dl-librecon.h */ |