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>
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1 changed files with 16 additions and 1 deletions
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@ -24,6 +24,7 @@
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#include <linux/personality.h>
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#include <linux/mm.h>
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#include <linux/random.h>
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#include <linux/sched.h>
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/*
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@ -45,6 +46,20 @@ static inline int mmap_is_legacy(void)
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return sysctl_legacy_va_layout;
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}
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static unsigned long mmap_rnd(void)
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{
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unsigned long rnd = 0;
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if (current->flags & PF_RANDOMIZE) {
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/* 8MB for 32bit, 1GB for 64bit */
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if (is_32bit_task())
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rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT)));
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else
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rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT)));
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}
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return rnd << PAGE_SHIFT;
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}
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static inline unsigned long mmap_base(void)
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{
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unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
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@ -54,7 +69,7 @@ static inline unsigned long mmap_base(void)
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else if (gap > MAX_GAP)
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gap = MAX_GAP;
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return TASK_SIZE - (gap & PAGE_MASK);
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return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd());
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}
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/*
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