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authorAlexandre Ghiti <alex@ghiti.fr>2019-09-24 01:38:47 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-09-25 01:54:11 +0300
commit67f3977f805b34cf0e41090679800d2091d41d49 (patch)
tree890420983b1d78727127650080058e6fea253d01 /mm/util.c
parente8d54b62c55ab6201de6d195fc2c276294c1f6ae (diff)
downloadlinux-67f3977f805b34cf0e41090679800d2091d41d49.tar.xz
arm64, mm: move generic mmap layout functions to mm
arm64 handles top-down mmap layout in a way that can be easily reused by other architectures, so make it available in mm. It then introduces a new config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT that can be set by other architectures to benefit from those functions. Note that this new config depends on MMU being enabled, if selected without MMU support, a warning will be thrown. Link: http://lkml.kernel.org/r/20190730055113.23635-5-alex@ghiti.fr Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> Suggested-by: Christoph Hellwig <hch@infradead.org> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Kees Cook <keescook@chromium.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: James Hogan <jhogan@kernel.org> Cc: Palmer Dabbelt <palmer@sifive.com> Cc: Paul Burton <paul.burton@mips.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/util.c')
-rw-r--r--mm/util.c78
1 files changed, 77 insertions, 1 deletions
diff --git a/mm/util.c b/mm/util.c
index bf8af5e07c4a..7922726f0a8f 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -17,7 +17,12 @@
#include <linux/vmalloc.h>
#include <linux/userfaultfd_k.h>
#include <linux/elf.h>
+#include <linux/elf-randomize.h>
+#include <linux/personality.h>
#include <linux/random.h>
+#include <linux/processor.h>
+#include <linux/sizes.h>
+#include <linux/compat.h>
#include <linux/uaccess.h>
@@ -315,7 +320,78 @@ unsigned long randomize_stack_top(unsigned long stack_top)
#endif
}
-#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
+#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
+#ifdef CONFIG_ARCH_HAS_ELF_RANDOMIZE
+unsigned long arch_mmap_rnd(void)
+{
+ unsigned long rnd;
+
+#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
+ if (is_compat_task())
+ rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
+ else
+#endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */
+ rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
+
+ return rnd << PAGE_SHIFT;
+}
+#endif /* CONFIG_ARCH_HAS_ELF_RANDOMIZE */
+
+static int mmap_is_legacy(struct rlimit *rlim_stack)
+{
+ if (current->personality & ADDR_COMPAT_LAYOUT)
+ return 1;
+
+ if (rlim_stack->rlim_cur == RLIM_INFINITY)
+ return 1;
+
+ return sysctl_legacy_va_layout;
+}
+
+/*
+ * Leave enough space between the mmap area and the stack to honour ulimit in
+ * the face of randomisation.
+ */
+#define MIN_GAP (SZ_128M)
+#define MAX_GAP (STACK_TOP / 6 * 5)
+
+static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
+{
+ unsigned long gap = rlim_stack->rlim_cur;
+ unsigned long pad = stack_guard_gap;
+
+ /* Account for stack randomization if necessary */
+ if (current->flags & PF_RANDOMIZE)
+ pad += (STACK_RND_MASK << PAGE_SHIFT);
+
+ /* Values close to RLIM_INFINITY can overflow. */
+ if (gap + pad > gap)
+ gap += pad;
+
+ if (gap < MIN_GAP)
+ gap = MIN_GAP;
+ else if (gap > MAX_GAP)
+ gap = MAX_GAP;
+
+ return PAGE_ALIGN(STACK_TOP - gap - rnd);
+}
+
+void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
+{
+ unsigned long random_factor = 0UL;
+
+ if (current->flags & PF_RANDOMIZE)
+ random_factor = arch_mmap_rnd();
+
+ if (mmap_is_legacy(rlim_stack)) {
+ mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
+ mm->get_unmapped_area = arch_get_unmapped_area;
+ } else {
+ mm->mmap_base = mmap_base(random_factor, rlim_stack);
+ mm->get_unmapped_area = arch_get_unmapped_area_topdown;
+ }
+}
+#elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
{
mm->mmap_base = TASK_UNMAPPED_BASE;