linux-kernel - [Patch v3 2/7] x86, kaslr: Introduce struct slot

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Message-Id: <1425793135-2833-3-git-send-email-bhe@redhat.com>
Date:	Sun,  8 Mar 2015 13:38:50 +0800
From:	Baoquan He <bhe@...hat.com>
To:	keescook@...omium.org, yinghai@...nel.org, hpa@...or.com,
	mingo@...hat.com, bp@...e.de, matt.fleming@...el.com,
	vgoyal@...hat.com, tglx@...utronix.de
Cc:	linux-kernel@...r.kernel.org, Baoquan He <bhe@...hat.com>
Subject: [Patch v3 2/7] x86, kaslr: Introduce struct slot_area to manage randomization slot info

Kernel is expected to be randomly reloaded anywhere in the whole
physical memory area, it could be near 64T at most. In this case
there could be about 4*1024*1024 randomization slots. Hence the
old slot array will cost too much memory and also not efficient
to store the slot information one by one into slot array.

Here introduce struct slot_area to manage randomization slot info
in one contiguous memory area excluding the avoid area. slot_areas
is used to store all slot area info. Since setup_data is a linked
list, could contain many datas by pointer to point one by one,
excluding them will split RAM memory into many smaller areas, here
only take the first 100 slot areas if too many of them.

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 arch/x86/boot/compressed/aslr.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
index 34eb652..c452a60 100644
--- a/arch/x86/boot/compressed/aslr.c
+++ b/arch/x86/boot/compressed/aslr.c
@@ -232,8 +232,20 @@ static bool mem_avoid_overlap(struct mem_vector *img)

 static unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
 			   CONFIG_PHYSICAL_ALIGN];
+
+struct slot_area {
+	unsigned long addr;
+	int num;
+};
+
+#define MAX_SLOT_AREA 100
+
+static struct slot_area slot_areas[MAX_SLOT_AREA];
+
 static unsigned long slot_max;

+static unsigned long slot_area_index;
+
 static void slots_append(unsigned long addr)
 {
 	/* Overflowing the slots list should be impossible. */
-- 
1.9.3

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