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authorBaoquan He <bhe@redhat.com>2019-03-08 10:56:16 +0800
committerThomas Gleixner <tglx@linutronix.de>2019-04-05 22:13:52 +0200
commitb569c18434987163a05f05a12cdf6a9975c55ff3 (patch)
tree3f88695ffdb9aacd44e4546c1a521160e55767ea /arch/x86/mm/kaslr.c
parent0925dda5962e9b55e4d38a72eba93858f24bac41 (diff)
x86/mm/KASLR: Reduce randomization granularity for 5-level paging to 1GB
The current randomization granularity of 5-level is 512 GB. The mapping of the real mode trampoline has been reduced to one PUD entry, so there is no restriction anymore. Reduce the granularity to 1GB for 5-level paging mode which allows better randomization. [ tglx: Massaged changelog ] Signed-off-by: Baoquan He <bhe@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: dave.hansen@linux.intel.com Cc: luto@kernel.org Cc: peterz@infradead.org Cc: bp@alien8.de Cc: hpa@zytor.com Cc: keescook@chromium.org Cc: thgarnie@google.com Link: https://lkml.kernel.org/r/20190308025616.21440-3-bhe@redhat.com
Diffstat (limited to 'arch/x86/mm/kaslr.c')
-rw-r--r--arch/x86/mm/kaslr.c10
1 files changed, 2 insertions, 8 deletions
diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
index 97813751340d..f6ba2791eeb5 100644
--- a/arch/x86/mm/kaslr.c
+++ b/arch/x86/mm/kaslr.c
@@ -125,10 +125,7 @@ void __init kernel_randomize_memory(void)
*/
entropy = remain_entropy / (ARRAY_SIZE(kaslr_regions) - i);
prandom_bytes_state(&rand_state, &rand, sizeof(rand));
- if (pgtable_l5_enabled())
- entropy = (rand % (entropy + 1)) & P4D_MASK;
- else
- entropy = (rand % (entropy + 1)) & PUD_MASK;
+ entropy = (rand % (entropy + 1)) & PUD_MASK;
vaddr += entropy;
*kaslr_regions[i].base = vaddr;
@@ -137,10 +134,7 @@ void __init kernel_randomize_memory(void)
* randomization alignment.
*/
vaddr += get_padding(&kaslr_regions[i]);
- if (pgtable_l5_enabled())
- vaddr = round_up(vaddr + 1, P4D_SIZE);
- else
- vaddr = round_up(vaddr + 1, PUD_SIZE);
+ vaddr = round_up(vaddr + 1, PUD_SIZE);
remain_entropy -= entropy;
}
}