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authorDavid S. Miller <davem@davemloft.net>2011-02-18 17:06:47 -0500
committerDavid S. Miller <davem@davemloft.net>2011-03-16 21:19:12 -0400
commit5a0efea09f42f7c92bd98a38d66b4dff9589266b (patch)
treef61f4d7e0e9f538110596899017b3a405964157e /arch/sparc
parentfd49bf48cac7126a8311592bea56518529a223e2 (diff)
sparc64: Sharpen address space randomization calculations.
A recent patch to the x86 randomization code caused me to take a quick look at what we do on sparc64, and in doing so I noticed that we sometimes calculate a non-page-aligned randomization value and stick it into mmap_base. I also noticed that since I copied the logic over from PowerPC, the powerpc code has tweaked the randomization ranges in ways that would benefit us as well. For one thing, we should allow up to at least 8MB of randomization otherwise huge-page regions when HPAGE_SIZE is 4MB never randomize at all. And on the 64-bit side we were using up to 4GB. Tone it down to 1GB as 4GB can result in a lot of address space wastage. Finally, make sure all computations are unsigned. Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/sparc')
-rw-r--r--arch/sparc/kernel/sys_sparc_64.c21
1 files changed, 13 insertions, 8 deletions
diff --git a/arch/sparc/kernel/sys_sparc_64.c b/arch/sparc/kernel/sys_sparc_64.c
index f836f4e93af..96082d30def 100644
--- a/arch/sparc/kernel/sys_sparc_64.c
+++ b/arch/sparc/kernel/sys_sparc_64.c
@@ -360,20 +360,25 @@ unsigned long get_fb_unmapped_area(struct file *filp, unsigned long orig_addr, u
360} 360}
361EXPORT_SYMBOL(get_fb_unmapped_area); 361EXPORT_SYMBOL(get_fb_unmapped_area);
362 362
363/* Essentially the same as PowerPC... */ 363/* Essentially the same as PowerPC. */
364void arch_pick_mmap_layout(struct mm_struct *mm) 364static unsigned long mmap_rnd(void)
365{ 365{
366 unsigned long random_factor = 0UL; 366 unsigned long rnd = 0UL;
367 unsigned long gap;
368 367
369 if (current->flags & PF_RANDOMIZE) { 368 if (current->flags & PF_RANDOMIZE) {
370 random_factor = get_random_int(); 369 unsigned long val = get_random_int();
371 if (test_thread_flag(TIF_32BIT)) 370 if (test_thread_flag(TIF_32BIT))
372 random_factor &= ((1 * 1024 * 1024) - 1); 371 rnd = (val % (1UL << (22UL-PAGE_SHIFT)));
373 else 372 else
374 random_factor = ((random_factor << PAGE_SHIFT) & 373 rnd = (val % (1UL << (29UL-PAGE_SHIFT)));
375 0xffffffffUL);
376 } 374 }
375 return (rnd << PAGE_SHIFT) * 2;
376}
377
378void arch_pick_mmap_layout(struct mm_struct *mm)
379{
380 unsigned long random_factor = mmap_rnd();
381 unsigned long gap;
377 382
378 /* 383 /*
379 * Fall back to the standard layout if the personality 384 * Fall back to the standard layout if the personality