diff options
| author | Anton Blanchard <anton@samba.org> | 2009-02-22 01:50:01 +0000 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2009-02-23 15:53:07 +1100 |
| commit | 9f14c42d7582bf33bbe1e133d897a6942ceae08e (patch) | |
| tree | fe95aaa735051496863f81f413afb2d3c128fb75 | |
| parent | 13a2cb3694d7237e6cc3e94fcb311b81908ccd06 (diff) | |
powerpc: Randomise mmap start address
Randomise mmap start address - 8MB on 32bit and 1GB on 64bit tasks.
Until ppc32 uses the mmap.c functionality, this is ppc64 specific.
Before:
# ./test & cat /proc/${!}/maps|tail -2|head -1
f75fe000-f7fff000 rw-p f75fe000 00:00 0
f75fe000-f7fff000 rw-p f75fe000 00:00 0
f75fe000-f7fff000 rw-p f75fe000 00:00 0
f75fe000-f7fff000 rw-p f75fe000 00:00 0
f75fe000-f7fff000 rw-p f75fe000 00:00 0
After:
# ./test & cat /proc/${!}/maps|tail -2|head -1
f718b000-f7b8c000 rw-p f718b000 00:00 0
f7551000-f7f52000 rw-p f7551000 00:00 0
f6ee7000-f78e8000 rw-p f6ee7000 00:00 0
f74d4000-f7ed5000 rw-p f74d4000 00:00 0
f6e9d000-f789e000 rw-p f6e9d000 00:00 0
Similar for 64bit, but with 1GB of scatter:
# ./test & cat /proc/${!}/maps|tail -2|head -1
fffb97b5000-fffb97b6000 rw-p fffb97b5000 00:00 0
fffce9a3000-fffce9a4000 rw-p fffce9a3000 00:00 0
fffeaaf2000-fffeaaf3000 rw-p fffeaaf2000 00:00 0
fffd88ac000-fffd88ad000 rw-p fffd88ac000 00:00 0
fffbc62e000-fffbc62f000 rw-p fffbc62e000 00:00 0
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
| -rw-r--r-- | arch/powerpc/mm/mmap.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c index 8ff5757af0d7..f7376dbb653b 100644 --- a/arch/powerpc/mm/mmap.c +++ b/arch/powerpc/mm/mmap.c @@ -24,6 +24,7 @@ #include <linux/personality.h> #include <linux/mm.h> +#include <linux/random.h> #include <linux/sched.h> /* @@ -45,6 +46,20 @@ static inline int mmap_is_legacy(void) return sysctl_legacy_va_layout; } +static unsigned long mmap_rnd(void) +{ + unsigned long rnd = 0; + + if (current->flags & PF_RANDOMIZE) { + /* 8MB for 32bit, 1GB for 64bit */ + if (is_32bit_task()) + rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT))); + else + rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT))); + } + return rnd << PAGE_SHIFT; +} + static inline unsigned long mmap_base(void) { unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur; @@ -54,7 +69,7 @@ static inline unsigned long mmap_base(void) else if (gap > MAX_GAP) gap = MAX_GAP; - return TASK_SIZE - (gap & PAGE_MASK); + return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd()); } /* |