[kernel-hardening] [PATCH v3 1/4] x86/mm: Adapt MODULES_END based on Fixmap section size

[Thomas Garnier <thgarnie@google.com>]

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-20170213
---
 arch/x86/include/asm/fixmap.h           | 8 ++++++++
 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 +
 5 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
index 8554f960e21b..20231189e0e3 100644
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -132,6 +132,14 @@ enum fixed_addresses {
 
 extern void reserve_top_address(unsigned long reserve);
 
+/* On 64-bit, the module sections ends with the start of the fixmap */
+#ifdef CONFIG_X86_64
+#define MODULES_VADDR    (__START_KERNEL_map + KERNEL_IMAGE_SIZE)
+#define MODULES_END   __fix_to_virt(__end_of_fixed_addresses + 1)
+#define MODULES_LEN   (MODULES_END - MODULES_VADDR)
+#endif /* CONFIG_X86_64 */
+
+
 #define FIXADDR_SIZE	(__end_of_permanent_fixed_addresses << PAGE_SHIFT)
 #define FIXADDR_START		(FIXADDR_TOP - FIXADDR_SIZE)
 
diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
index 3a264200c62f..de8bace10200 100644
--- a/arch/x86/include/asm/pgtable_64_types.h
+++ b/arch/x86/include/asm/pgtable_64_types.h
@@ -66,9 +66,6 @@ typedef struct { pteval_t pte; } pte_t;
 #define VMEMMAP_START	__VMEMMAP_BASE
 #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)
-#define MODULES_LEN   (MODULES_END - MODULES_VADDR)
 #define ESPFIX_PGD_ENTRY _AC(-2, UL)
 #define ESPFIX_BASE_ADDR (ESPFIX_PGD_ENTRY << PGDIR_SHIFT)
 #define EFI_VA_START	 ( -4 * (_AC(1, UL) << 30))
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 8aa6bea1cd6c..90170415f08a 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -19,6 +19,7 @@
 #include <linux/seq_file.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 0493c17b8a51..34f167cf3316 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -8,6 +8,7 @@
 
 #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];
-- 
2.11.0.483.g087da7b7c-goog