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authorDan McGee <dpmcgee@gmail.com>2011-10-17 13:05:23 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2011-11-28 11:42:09 +1100
commitfa8cbaaf5a68f62db3f9a8444ecbb940b47984cb (patch)
treeef8c31c149c7f1fb6c504e7556dab3e56212c539 /arch
parent3ce21cdfe93efffa4ffba9cf3ca2576d3d60d6dc (diff)
downloadvexpress-lsk-fa8cbaaf5a68f62db3f9a8444ecbb940b47984cb.tar.gz
powerpc+sparc64/mm: Remove hack in mmap randomize layout
Since commit 8a0a9bd4db63bc45e301, this comment in mmap_rnd() does not hold true as the value returned by get_random_int() will in fact be different every single call. Remove the comment and simplify the code back to its original desired form. This reverts commit a5adc91a4b44b5d1 which is no longer necessary and also fixes the sparc code that copied this same adjustment. Signed-off-by: Dan McGee <dpmcgee@gmail.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/mm/mmap_64.c14
-rw-r--r--arch/sparc/kernel/sys_sparc_64.c6
2 files changed, 6 insertions, 14 deletions
diff --git a/arch/powerpc/mm/mmap_64.c b/arch/powerpc/mm/mmap_64.c
index 5a783d8e8e8..67a42ed0d2f 100644
--- a/arch/powerpc/mm/mmap_64.c
+++ b/arch/powerpc/mm/mmap_64.c
@@ -53,14 +53,6 @@ static inline int mmap_is_legacy(void)
return sysctl_legacy_va_layout;
}
-/*
- * Since get_random_int() returns the same value within a 1 jiffy window,
- * we will almost always get the same randomisation for the stack and mmap
- * region. This will mean the relative distance between stack and mmap will
- * be the same.
- *
- * To avoid this we can shift the randomness by 1 bit.
- */
static unsigned long mmap_rnd(void)
{
unsigned long rnd = 0;
@@ -68,11 +60,11 @@ static unsigned long mmap_rnd(void)
if (current->flags & PF_RANDOMIZE) {
/* 8MB for 32bit, 1GB for 64bit */
if (is_32bit_task())
- rnd = (long)(get_random_int() % (1<<(22-PAGE_SHIFT)));
+ rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT)));
else
- rnd = (long)(get_random_int() % (1<<(29-PAGE_SHIFT)));
+ rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT)));
}
- return (rnd << PAGE_SHIFT) * 2;
+ return rnd << PAGE_SHIFT;
}
static inline unsigned long mmap_base(void)
diff --git a/arch/sparc/kernel/sys_sparc_64.c b/arch/sparc/kernel/sys_sparc_64.c
index 441521ad8a3..232df994953 100644
--- a/arch/sparc/kernel/sys_sparc_64.c
+++ b/arch/sparc/kernel/sys_sparc_64.c
@@ -368,11 +368,11 @@ static unsigned long mmap_rnd(void)
if (current->flags & PF_RANDOMIZE) {
unsigned long val = get_random_int();
if (test_thread_flag(TIF_32BIT))
- rnd = (val % (1UL << (22UL-PAGE_SHIFT)));
+ rnd = (val % (1UL << (23UL-PAGE_SHIFT)));
else
- rnd = (val % (1UL << (29UL-PAGE_SHIFT)));
+ rnd = (val % (1UL << (30UL-PAGE_SHIFT)));
}
- return (rnd << PAGE_SHIFT) * 2;
+ return rnd << PAGE_SHIFT;
}
void arch_pick_mmap_layout(struct mm_struct *mm)