linux-kernel - [PATCH 6/6] extend the upper limit of kernel physical address randomization to 4G

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Date:	Wed, 21 Jan 2015 11:37:17 +0800
From:	Baoquan He <bhe@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	x86@...nel.org, keescook@...omium.org, vgoyal@...hat.com,
	whissi@...ssi.de, Baoquan He <bhe@...hat.com>
Subject: [PATCH 6/6] extend the upper limit of kernel physical address randomization to 4G

Since now kaslr can separately do randomization of physical and virtual
address, the physical address doesn't have to be
CONFIG_RANDOMIZE_BASE_MAX_OFFSET any more. At this time the identity
mapping only covers [0, 4G], so extend the upper limit of kernel physical
address randomization to 4G.

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 arch/x86/boot/compressed/aslr.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
index 20a5f23..b112f90 100644
--- a/arch/x86/boot/compressed/aslr.c
+++ b/arch/x86/boot/compressed/aslr.c
@@ -207,14 +207,15 @@ static bool mem_avoid_overlap(struct mem_vector *img)
 	return false;
 }
 
-static unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
+#define PHYS_RANDOM_UPPER_LIMIT 0x100000000UL
+static unsigned long slots[PHYS_RANDOM_UPPER_LIMIT /
 			   CONFIG_PHYSICAL_ALIGN];
 static unsigned long slot_max;
 
 static void slots_append(unsigned long addr)
 {
 	/* Overflowing the slots list should be impossible. */
-	if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
+	if (slot_max >= PHYS_RANDOM_UPPER_LIMIT /
 			CONFIG_PHYSICAL_ALIGN)
 		return;
 
@@ -241,7 +242,7 @@ static void process_e820_entry(struct e820entry *entry,
 		return;
 
 	/* Ignore entries entirely above our maximum. */
-	if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
+	if (entry->addr >= PHYS_RANDOM_UPPER_LIMIT)
 		return;
 
 	/* Ignore entries entirely below our minimum. */
@@ -266,8 +267,8 @@ static void process_e820_entry(struct e820entry *entry,
 	region.size -= region.start - entry->addr;
 
 	/* Reduce maximum size to fit end of image within maximum limit. */
-	if (region.start + region.size > CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
-		region.size = CONFIG_RANDOMIZE_BASE_MAX_OFFSET - region.start;
+	if (region.start + region.size  > PHYS_RANDOM_UPPER_LIMIT)
+		region.size = PHYS_RANDOM_UPPER_LIMIT - region.start;
 
 	/* Walk each aligned slot and check for avoided areas. */
 	for (img.start = region.start, img.size = image_size ;
-- 
1.9.3

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