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powerpc: More stack randomisation for 64bit binaries

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At the moment we randomise the stack by 8MB on 32bit and 64bit tasks. Since we
have a lot more address space to play with on 64bit, lets do what x86 does and
increase that randomisation to 1GB:

before:
# for i in seq `1 10` ; do sleep 1 & cat /proc/${!}/maps | grep stack; done
fffffebc000-fffffed1000 rw-p ffffffeb000 00:00 0       [stack]
ffffff5a000-ffffff6f000 rw-p ffffffeb000 00:00 0       [stack]
fffffdb2000-fffffdc7000 rw-p ffffffeb000 00:00 0       [stack]
fffffd3e000-fffffd53000 rw-p ffffffeb000 00:00 0       [stack]
fffffad9000-fffffaee000 rw-p ffffffeb000 00:00 0       [stack]

after:
# for i in seq `1 10` ; do sleep 1 & cat /proc/${!}/maps | grep stack; done
ffff5c27000-ffff5c3c000 rw-p ffffffeb000 00:00 0       [stack]
fffebe5e000-fffebe73000 rw-p ffffffeb000 00:00 0       [stack]
fffcb298000-fffcb2ad000 rw-p ffffffeb000 00:00 0       [stack]
fffc719d000-fffc71b2000 rw-p ffffffeb000 00:00 0       [stack]
fffe01af000-fffe01c4000 rw-p ffffffeb000 00:00 0       [stack]

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Anton Blanchard 2009-02-22 01:50:02 +00:00 committed by Benjamin Herrenschmidt
parent 9f14c42d75
commit 2dadb987e0
1 changed files with 5 additions and 0 deletions
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5
arch/powerpc/include/asm/elf.h
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@ -271,6 +271,11 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm,
int uses_interp);
#define VDSO_AUX_ENT(a,b) NEW_AUX_ENT(a,b);
/* 1GB for 64bit, 8MB for 32bit */
#define STACK_RND_MASK (is_32bit_task() ? \
(0x7ff >> (PAGE_SHIFT - 12)) : \
(0x3ffff >> (PAGE_SHIFT - 12)))
#endif /* __KERNEL__ */
/*