linux-kernel - [PATCH 1/3] x86/KASLR: Update KERNEL_IMAGE

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Message-Id: <20181006084327.27467-2-bhe@redhat.com>
Date:   Sat,  6 Oct 2018 16:43:25 +0800
From:   Baoquan He <bhe@...hat.com>
To:     mingo@...nel.org
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-doc@...r.kernel.org, tglx@...utronix.de, thgarnie@...gle.com,
        corbet@....net, Baoquan He <bhe@...hat.com>
Subject: [PATCH 1/3] 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old comments above the KERNEL_IMAGE_SIZE definition out of date.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 <bhe@...hat.com>
---
 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 6afac386a434..cd0cf1c568b4 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)
-- 
2.13.6