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Subject[PATCH v2] tile: support ASLR fully
With this change, tile Linux now supports address-space layout
randomization for shared objects, stack, heap and vdso.

Signed-off-by: Tony Lu <zlu@tilera.com>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
---
v2: implement Jiri Kosina's suggestion to copy the math in
mmap_rnd() for x86.

arch/tile/include/asm/elf.h | 4 ++++
arch/tile/mm/mmap.c | 24 ++++++++++++++++++++++--
2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/arch/tile/include/asm/elf.h b/arch/tile/include/asm/elf.h
index 31d854f..e1da88e 100644
--- a/arch/tile/include/asm/elf.h
+++ b/arch/tile/include/asm/elf.h
@@ -137,6 +137,10 @@ do { \
NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_BASE); \
} while (0)

+struct mm_struct;
+extern unsigned long arch_randomize_brk(struct mm_struct *mm);
+#define arch_randomize_brk arch_randomize_brk
+
#ifdef CONFIG_COMPAT

#define COMPAT_ELF_PLATFORM "tilegx-m32"
diff --git a/arch/tile/mm/mmap.c b/arch/tile/mm/mmap.c
index d67d91e..4b99344 100644
--- a/arch/tile/mm/mmap.c
+++ b/arch/tile/mm/mmap.c
@@ -58,16 +58,36 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
#else
int is_32bit = 0;
#endif
+ unsigned long random_factor = 0UL;
+
+ /*
+ * 8 bits of randomness in 32bit mmaps, 24 address space bits
+ * 12 bits of randomness in 64bit mmaps, 28 address space bits
+ */
+ if (current->flags & PF_RANDOMIZE) {
+ if (is_32bit)
+ random_factor = get_random_int() % (1<<8);
+ else
+ random_factor = get_random_int() % (1<<12);
+
+ random_factor <<= PAGE_SHIFT;
+ }

/*
* Use standard layout if the expected stack growth is unlimited
* or we are running native 64 bits.
*/
- if (!is_32bit || rlimit(RLIMIT_STACK) == RLIM_INFINITY) {
- mm->mmap_base = TASK_UNMAPPED_BASE;
+ if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) {
+ mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
mm->get_unmapped_area = arch_get_unmapped_area;
} else {
mm->mmap_base = mmap_base(mm);
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
}
}
+
+unsigned long arch_randomize_brk(struct mm_struct *mm)
+{
+ unsigned long range_end = mm->brk + 0x02000000;
+ return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
+}
--
1.8.3.1


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