diff options
Diffstat (limited to 'sysdeps')
| -rw-r--r-- | sysdeps/generic/malloc-sysdep.h | 25 | ||||
| -rw-r--r-- | sysdeps/unix/sysv/linux/malloc-sysdep.h | 57 |
2 files changed, 82 insertions, 0 deletions
diff --git a/sysdeps/generic/malloc-sysdep.h b/sysdeps/generic/malloc-sysdep.h new file mode 100644 index 0000000000..bbc48c04f0 --- /dev/null +++ b/sysdeps/generic/malloc-sysdep.h @@ -0,0 +1,25 @@ +/* System-specific malloc support functions. Generic version. + Copyright (C) 2012 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/>. */ + +/* Force an unmap when the heap shrinks in a secure exec. This ensures that + the old data pages immediately cease to be accessible. */ +static inline bool +check_may_shrink_heap (void) +{ + return __libc_enable_secure; +} diff --git a/sysdeps/unix/sysv/linux/malloc-sysdep.h b/sysdeps/unix/sysv/linux/malloc-sysdep.h new file mode 100644 index 0000000000..f926aeafff --- /dev/null +++ b/sysdeps/unix/sysv/linux/malloc-sysdep.h @@ -0,0 +1,57 @@ +/* System-specific malloc support functions. Linux version. + Copyright (C) 2012 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/>. */ + +#include <fcntl.h> +#include <not-cancel.h> + +/* The Linux kernel overcommits address space by default and if there is not + enough memory available, it uses various parameters to decide the process to + kill. It is however possible to disable or curb this overcommit behavior + by setting the proc sysctl vm.overcommit_memory to the value '2' and with + that, a process is only allowed to use the maximum of a pre-determined + fraction of the total address space. In such a case, we want to make sure + that we are judicious with our heap usage as well, and explicitly give away + the freed top of the heap to reduce our commit charge. See the proc(5) man + page to know more about overcommit behavior. + + Other than that, we also force an unmap in a secure exec. */ +static inline bool +check_may_shrink_heap (void) +{ + static int may_shrink_heap = -1; + + if (__builtin_expect (may_shrink_heap >= 0, 1)) + return may_shrink_heap; + + may_shrink_heap = __libc_enable_secure; + + if (__builtin_expect (may_shrink_heap == 0, 1)) + { + int fd = open_not_cancel_2 ("/proc/sys/vm/overcommit_memory", + O_RDONLY | O_CLOEXEC); + if (fd >= 0) + { + char val; + ssize_t n = read_not_cancel (fd, &val, 1); + may_shrink_heap = n > 0 && val == '2'; + close_not_cancel_no_status (fd); + } + } + + return may_shrink_heap; +} |