From 9f14c42d7582bf33bbe1e133d897a6942ceae08e Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Sun, 22 Feb 2009 01:50:01 +0000 Subject: [PATCH] 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 Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/mm/mmap.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) 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 #include +#include #include /* @@ -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()); } /* -- 2.20.1