From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Andr=C3=A9=20Fabian=20Silva=20Delgado?= Date: Wed, 5 Aug 2015 17:04:01 -0300 Subject: Initial import --- arch/x86/mm/mmap.c | 135 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 135 insertions(+) create mode 100644 arch/x86/mm/mmap.c (limited to 'arch/x86/mm/mmap.c') diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c new file mode 100644 index 000000000..844b06d67 --- /dev/null +++ b/arch/x86/mm/mmap.c @@ -0,0 +1,135 @@ +/* + * Flexible mmap layout support + * + * Based on code by Ingo Molnar and Andi Kleen, copyrighted + * as follows: + * + * Copyright 2003-2009 Red Hat Inc. + * All Rights Reserved. + * Copyright 2005 Andi Kleen, SUSE Labs. + * Copyright 2007 Jiri Kosina, SUSE Labs. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#include +#include +#include +#include +#include +#include + +struct va_alignment __read_mostly va_align = { + .flags = -1, +}; + +static unsigned long stack_maxrandom_size(void) +{ + unsigned long max = 0; + if ((current->flags & PF_RANDOMIZE) && + !(current->personality & ADDR_NO_RANDOMIZE)) { + max = ((-1UL) & STACK_RND_MASK) << PAGE_SHIFT; + } + + return max; +} + +/* + * Top of mmap area (just below the process stack). + * + * Leave an at least ~128 MB hole with possible stack randomization. + */ +#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size()) +#define MAX_GAP (TASK_SIZE/6*5) + +static int mmap_is_legacy(void) +{ + if (current->personality & ADDR_COMPAT_LAYOUT) + return 1; + + if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) + return 1; + + return sysctl_legacy_va_layout; +} + +unsigned long arch_mmap_rnd(void) +{ + unsigned long rnd; + + /* + * 8 bits of randomness in 32bit mmaps, 20 address space bits + * 28 bits of randomness in 64bit mmaps, 40 address space bits + */ + if (mmap_is_ia32()) + rnd = (unsigned long)get_random_int() % (1<<8); + else + rnd = (unsigned long)get_random_int() % (1<<28); + + return rnd << PAGE_SHIFT; +} + +static unsigned long mmap_base(unsigned long rnd) +{ + unsigned long gap = rlimit(RLIMIT_STACK); + + if (gap < MIN_GAP) + gap = MIN_GAP; + else if (gap > MAX_GAP) + gap = MAX_GAP; + + return PAGE_ALIGN(TASK_SIZE - gap - rnd); +} + +/* + * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64 + * does, but not when emulating X86_32 + */ +static unsigned long mmap_legacy_base(unsigned long rnd) +{ + if (mmap_is_ia32()) + return TASK_UNMAPPED_BASE; + else + return TASK_UNMAPPED_BASE + rnd; +} + +/* + * This function, called very early during the creation of a new + * process VM image, sets up which VM layout function to use: + */ +void arch_pick_mmap_layout(struct mm_struct *mm) +{ + unsigned long random_factor = 0UL; + + if (current->flags & PF_RANDOMIZE) + random_factor = arch_mmap_rnd(); + + mm->mmap_legacy_base = mmap_legacy_base(random_factor); + + if (mmap_is_legacy()) { + mm->mmap_base = mm->mmap_legacy_base; + mm->get_unmapped_area = arch_get_unmapped_area; + } else { + mm->mmap_base = mmap_base(random_factor); + mm->get_unmapped_area = arch_get_unmapped_area_topdown; + } +} + +const char *arch_vma_name(struct vm_area_struct *vma) +{ + if (vma->vm_flags & VM_MPX) + return "[mpx]"; + return NULL; +} -- cgit v1.2.3