x86, kaslr: Raise the maximum virtual address to -1 GiB on x86_64

On 64-bit, this raises the maximum location to -1 GiB (from -1.5 GiB),
the upper limit currently, since the kernel fixmap page mappings need
to be moved to use the other 1 GiB (which would be the theoretical
limit when building with -mcmodel=kernel).

Signed-off-by: Kees Cook <keescook@chromium.org>
Link: http://lkml.kernel.org/r/1381450698-28710-7-git-send-email-keescook@chromium.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 4287f1ffba7e..5bdc5430597c 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -806,6 +806,9 @@ void __init mem_init(void)
         BUILD_BUG_ON(VMALLOC_START                      >= VMALLOC_END);
 #undef high_memory
 #undef __FIXADDR_TOP
+#ifdef CONFIG_RANDOMIZE_BASE
+        BUILD_BUG_ON(CONFIG_RANDOMIZE_BASE_MAX_OFFSET > KERNEL_IMAGE_SIZE);
+#endif
 
 #ifdef CONFIG_HIGHMEM
         BUG_ON(PKMAP_BASE + LAST_PKMAP*PAGE_SIZE        > FIXADDR_START);