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Subject[PATCH 11/30] x86, kaiser: make sure static PGDs are 8k in size
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From: Dave Hansen <dave.hansen@linux.intel.com>

We have a few PGDs that come out of the kernel binary instead of being
allocated dynamically. Before this patch, they are all 8k-aligned,
but we also need them to be 8k in *size*e

The original KAISER patch did not do this. It probably just lucked out
that it did not trample over data after the last PGD.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Moritz Lipp <moritz.lipp@iaik.tugraz.at>
Cc: Daniel Gruss <daniel.gruss@iaik.tugraz.at>
Cc: Michael Schwarz <michael.schwarz@iaik.tugraz.at>
Cc: Richard Fellner <richard.fellner@student.tugraz.at>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: x86@kernel.org
---

b/arch/x86/kernel/head_64.S | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff -puN arch/x86/kernel/head_64.S~kaiser-head_S-pgds-need-8k-too arch/x86/kernel/head_64.S
--- a/arch/x86/kernel/head_64.S~kaiser-head_S-pgds-need-8k-too 2017-11-08 10:45:31.840681389 -0800
+++ b/arch/x86/kernel/head_64.S 2017-11-08 10:45:31.843681389 -0800
@@ -340,11 +340,24 @@ GLOBAL(early_recursion_flag)
GLOBAL(name)

#ifdef CONFIG_KAISER
+/*
+ * Each PGD needs to be 8k long and 8k aligned. We do not
+ * ever go out to userspace with these, so we do not
+ * strictly *need* the second page, but this allows us to
+ * have a single set_pgd() implementation that does not
+ * need to worry about whether it has 4k or 8k to work
+ * with.
+ *
+ * This ensures PGDs are 8k long:
+ */
+#define KAISER_USER_PGD_FILL 512
+/* This ensures they are 8k-aligned: */
#define NEXT_PGD_PAGE(name) \
.balign 2 * PAGE_SIZE; \
GLOBAL(name)
#else
#define NEXT_PGD_PAGE(name) NEXT_PAGE(name)
+#define KAISER_USER_PGD_FILL 0
#endif

/* Automate the creation of 1 to 1 mapping pmd entries */
@@ -363,6 +376,7 @@ NEXT_PGD_PAGE(early_top_pgt)
#else
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
#endif
+ .fill KAISER_USER_PGD_FILL,8,0

NEXT_PAGE(early_dynamic_pgts)
.fill 512*EARLY_DYNAMIC_PAGE_TABLES,8,0
@@ -372,6 +386,7 @@ NEXT_PAGE(early_dynamic_pgts)
#ifndef CONFIG_XEN
NEXT_PGD_PAGE(init_top_pgt)
.fill 512,8,0
+ .fill KAISER_USER_PGD_FILL,8,0
#else
NEXT_PGD_PAGE(init_top_pgt)
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
@@ -380,6 +395,7 @@ NEXT_PGD_PAGE(init_top_pgt)
.org init_top_pgt + PGD_START_KERNEL*8, 0
/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
+ .fill KAISER_USER_PGD_FILL,8,0

NEXT_PAGE(level3_ident_pgt)
.quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
_
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