[kernel-hardening] [PATCH v5 1/3] x86/mm: Adapt MODULES_END based on Fixmap section size

Thomas Garnier
2017-03-06T22:03:46Z

This patch aligns MODULES_END to the beginning of the Fixmap section.
It optimizes the space available for both sections. The address is
pre-computed based on the number of pages required by the Fixmap
section.

It will allow GDT remapping in the Fixmap section. The current
MODULES_END static address does not provide enough space for the kernel
to support a large number of processors.

Signed-off-by: Thomas Garnier <thgarnie@google.com>
---
Based on next-20170306
---
Documentation/x86/x86_64/mm.txt | 5 ++++-
arch/x86/include/asm/pgtable_64_types.h | 3 ++-
arch/x86/kernel/module.c | 1 +
arch/x86/mm/dump_pagetables.c | 1 +
arch/x86/mm/kasan_init_64.c | 1 +
mm/vmalloc.c | 1 +
6 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt
index 5724092db811..ee3f9c30957c 100644
--- a/Documentation/x86/x86_64/mm.txt
+++ b/Documentation/x86/x86_64/mm.txt
@@ -19,7 +19,7 @@ ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks
ffffffef00000000 - fffffffeffffffff (=64 GB) EFI region mapping space
... unused hole ...
ffffffff80000000 - ffffffff9fffffff (=512 MB) kernel text mapping, from phys 0
-ffffffffa0000000 - ffffffffff5fffff (=1526 MB) module mapping space
+ffffffffa0000000 - ffffffffff5fffff (=1526 MB) module mapping space (variable)
ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls
ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole

@@ -39,6 +39,9 @@ memory window (this size is arbitrary, it can be raised later if needed).
The mappings are not part of any other kernel PGD and are only available
during EFI runtime calls.

+The module mapping space size changes based on the CONFIG requirements for the
+following fixmap section.
+
Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all
physical memory, vmalloc/ioremap space and virtual memory map are randomized.
Their order is preserved but their base will be offset early at boot time.
diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
index 3a264200c62f..bb05e21cf3c7 100644
--- a/arch/x86/include/asm/pgtable_64_types.h
+++ b/arch/x86/include/asm/pgtable_64_types.h
@@ -67,7 +67,8 @@ typedef struct { pteval_t pte; } pte_t;
#endif /* CONFIG_RANDOMIZE_MEMORY */
#define VMALLOC_END (VMALLOC_START + _AC((VMALLOC_SIZE_TB << 40) - 1, UL))
#define MODULES_VADDR (__START_KERNEL_map + KERNEL_IMAGE_SIZE)
-#define MODULES_END _AC(0xffffffffff000000, UL)
+/* The module sections ends with the start of the fixmap */
+#define MODULES_END __fix_to_virt(__end_of_fixed_addresses + 1)
#define MODULES_LEN (MODULES_END - MODULES_VADDR)
#define ESPFIX_PGD_ENTRY _AC(-2, UL)
#define ESPFIX_BASE_ADDR (ESPFIX_PGD_ENTRY << PGDIR_SHIFT)
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index 477ae806c2fa..fad61caac75e 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -35,6 +35,7 @@
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/setup.h>
+#include <asm/fixmap.h>

#if 0
#define DEBUGP(fmt, ...) \
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 58b5bee7ea27..75efeecc85eb 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -20,6 +20,7 @@

#include <asm/kasan.h>
#include <asm/pgtable.h>
+#include <asm/fixmap.h>

/*
* The dumper groups pagetable entries of the same type into one, and for
diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index 8d63d7a104c3..1bde19ef86bd 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -9,6 +9,7 @@

#include <asm/tlbflush.h>
#include <asm/sections.h>
+#include <asm/fixmap.h>

extern pgd_t early_level4_pgt[PTRS_PER_PGD];
extern struct range pfn_mapped[E820_X_MAX];
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index b4024d688f38..91b0d5e19af6 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -35,6 +35,7 @@
#include <linux/uaccess.h>
#include <asm/tlbflush.h>
#include <asm/shmparam.h>
+#include <asm/fixmap.h>

#include "internal.h"

--
2.12.0.rc1.440.g5b76565f74-goog