From 06d4a462e954756f3d3d54e6f3f1bdc2e6f592a9 Mon Sep 17 00:00:00 2001 From: Baoquan He Date: Sat, 6 Oct 2018 16:43:25 +0800 Subject: [PATCH] x86/KASLR: Update KERNEL_IMAGE_SIZE description Currently CONFIG_RANDOMIZE_BASE=y is set by default, which makes some of the old comments above the KERNEL_IMAGE_SIZE definition out of date. Update them to the current state of affairs. Signed-off-by: Baoquan He Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: corbet@lwn.net Cc: linux-doc@vger.kernel.org Cc: thgarnie@google.com Link: http://lkml.kernel.org/r/20181006084327.27467-2-bhe@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/page_64_types.h | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h index 6afac38..cd0cf1c 100644 --- a/arch/x86/include/asm/page_64_types.h +++ b/arch/x86/include/asm/page_64_types.h @@ -59,13 +59,16 @@ #endif /* - * Kernel image size is limited to 1GiB due to the fixmap living in the - * next 1GiB (see level2_kernel_pgt in arch/x86/kernel/head_64.S). Use - * 512MiB by default, leaving 1.5GiB for modules once the page tables - * are fully set up. If kernel ASLR is configured, it can extend the - * kernel page table mapping, reducing the size of the modules area. + * Maximum kernel image size is limited to 1 GiB, due to the fixmap living + * in the next 1 GiB (see level2_kernel_pgt in arch/x86/kernel/head_64.S). + * + * On KASLR use 1 GiB by default, leaving 1 GiB for modules once the + * page tables are fully set up. + * + * If KASLR is disabled we can shrink it to 0.5 GiB and increase the size + * of the modules area to 1.5 GiB. */ -#if defined(CONFIG_RANDOMIZE_BASE) +#ifdef CONFIG_RANDOMIZE_BASE #define KERNEL_IMAGE_SIZE (1024 * 1024 * 1024) #else #define KERNEL_IMAGE_SIZE (512 * 1024 * 1024) -- 2.7.4