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MIPS: Enable heap randomization.

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Based somewhat on the PPC implementation.

32-bit processes have the heap randomized in an 8MB space, 256MB for
64-bit processes.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1479/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
David Daney 2010-07-19 13:14:57 -07:00 • committed by Ralf Baechle
commit 652b14aa84
2 changed files with 33 additions and 0 deletions
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5
arch/mips/include/asm/elf.h
View file

@ -372,4 +372,9 @@ extern const char *__elf_platform;
struct linux_binprm;
extern int arch_setup_additional_pages(struct linux_binprm *bprm,
int uses_interp);
struct mm_struct;
extern unsigned long arch_randomize_brk(struct mm_struct *mm);
#define arch_randomize_brk arch_randomize_brk
#endif /* _ASM_ELF_H */

28
arch/mips/kernel/syscall.c
View file

@ -30,6 +30,7 @@
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/elf.h>
#include <asm/asm.h>
#include <asm/branch.h>
@ -153,6 +154,33 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
mm->unmap_area = arch_unmap_area;
}
static inline unsigned long brk_rnd(void)
{
unsigned long rnd = get_random_int();
rnd = rnd << PAGE_SHIFT;
/* 8MB for 32bit, 256MB for 64bit */
if (TASK_IS_32BIT_ADDR)
rnd = rnd & 0x7ffffful;
else
rnd = rnd & 0xffffffful;
return rnd;
}
unsigned long arch_randomize_brk(struct mm_struct *mm)
{
unsigned long base = mm->brk;
unsigned long ret;
ret = PAGE_ALIGN(base + brk_rnd());
if (ret < mm->brk)
return mm->brk;
return ret;
}
SYSCALL_DEFINE6(mips_mmap, unsigned long, addr, unsigned long, len,
unsigned long, prot, unsigned long, flags, unsigned long,
fd, off_t, offset)