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powerpc: Randomise the brk region

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Randomize the heap.

before:
tundro2:~ # sleep 1 & cat /proc/${!}/maps | grep heap
10017000-10118000 rw-p 10017000 00:00 0                                  [heap]
10017000-10118000 rw-p 10017000 00:00 0                                  [heap]
10017000-10118000 rw-p 10017000 00:00 0                                  [heap]
10017000-10118000 rw-p 10017000 00:00 0                                  [heap]
10017000-10118000 rw-p 10017000 00:00 0                                  [heap]

after
tundro2:~ # sleep 1 & cat /proc/${!}/maps | grep heap
19419000-1951a000 rw-p 19419000 00:00 0                                  [heap]
325ff000-32700000 rw-p 325ff000 00:00 0                                  [heap]
1a97c000-1aa7d000 rw-p 1a97c000 00:00 0                                  [heap]
1cc60000-1cd61000 rw-p 1cc60000 00:00 0                                  [heap]
1afa9000-1b0aa000 rw-p 1afa9000 00:00 0                                  [heap]

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 01:50:04 +00:00 committed by Benjamin Herrenschmidt
parent d839088cae
commit 912f9ee21c
2 changed files with 26 additions and 0 deletions
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3
arch/powerpc/include/asm/elf.h
View File

@ -276,6 +276,9 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm,
(0x7ff >> (PAGE_SHIFT - 12)) : \
(0x3ffff >> (PAGE_SHIFT - 12)))
extern unsigned long arch_randomize_brk(struct mm_struct *mm);
#define arch_randomize_brk arch_randomize_brk
#endif /* __KERNEL__ */
/*

23
arch/powerpc/kernel/process.c
View File

@ -1147,3 +1147,26 @@ unsigned long arch_align_stack(unsigned long sp)
sp -= get_random_int() & ~PAGE_MASK;
return sp & ~0xf;
}
static inline unsigned long brk_rnd(void)
{
unsigned long rnd = 0;
/* 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;
}
unsigned long arch_randomize_brk(struct mm_struct *mm)
{
unsigned long ret = PAGE_ALIGN(mm->brk + brk_rnd());
if (ret < mm->brk)
return mm->brk;
return ret;
}