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authorDavid S. Miller <davem@davemloft.net>2018-01-17 00:00:25 -0500
committerDavid S. Miller <davem@davemloft.net>2018-01-17 00:10:42 -0500
commitc02b3741eb99a1ec733e6134c53ba59e43e19e97 (patch)
treeff7dd96c32dec2abe530e7101378443dabcb8962 /arch/x86/kernel/tboot.c
parent7018d1b3f20fb4308ed9bc577160cb8ffb79b62a (diff)
parent8cbab92dff778e516064c13113ca15d4869ec883 (diff)
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Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Overlapping changes all over. The mini-qdisc bits were a little bit tricky, however. Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/x86/kernel/tboot.c')
-rw-r--r--arch/x86/kernel/tboot.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index a4eb27918ceb..a2486f444073 100644
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -138,6 +138,17 @@ static int map_tboot_page(unsigned long vaddr, unsigned long pfn,
return -1;
set_pte_at(&tboot_mm, vaddr, pte, pfn_pte(pfn, prot));
pte_unmap(pte);
+
+ /*
+ * PTI poisons low addresses in the kernel page tables in the
+ * name of making them unusable for userspace. To execute
+ * code at such a low address, the poison must be cleared.
+ *
+ * Note: 'pgd' actually gets set in p4d_alloc() _or_
+ * pud_alloc() depending on 4/5-level paging.
+ */
+ pgd->pgd &= ~_PAGE_NX;
+
return 0;
}