linux-kernel - [PATCH v2 7/9] get the random phy addr according to slot

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Date:	Mon,  2 Mar 2015 22:58:28 +0800
From:	Baoquan He <bhe@...hat.com>
To:	hpa@...or.com, yinghai@...nel.org, keescook@...omium.org,
	vgoyal@...hat.com, luto@...capital.net, akpm@...ux-foundation.org,
	tglx@...utronix.de, mingo@...hat.com
Cc:	linux-kernel@...r.kernel.org, Baoquan He <bhe@...hat.com>
Subject: [PATCH v2 7/9] get the random phy addr according to slot_area info

Now random value can be used to get related slot info stored in
slot_area, mainly use slot_area.num to position which slot is target.
With this slot its starting address is returned as the physical
address where kernel will put.

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 arch/x86/boot/compressed/aslr.c | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
index 1c6fb31..55adee2 100644
--- a/arch/x86/boot/compressed/aslr.c
+++ b/arch/x86/boot/compressed/aslr.c
@@ -245,9 +245,6 @@ static unsigned long mem_min_overlap(struct mem_vector *img, struct mem_vector *
 	return min;
 }
 
-static unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
-			   CONFIG_PHYSICAL_ALIGN];
-
 struct slot_area {
 	unsigned long addr;
 	int num;
@@ -261,23 +258,28 @@ 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. */
-	if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
-			CONFIG_PHYSICAL_ALIGN)
-		return;
-
-	slots[slot_max++] = addr;
-}
-
 static unsigned long slots_fetch_random(void)
 {
+	unsigned long random;
+	int i;
+
 	/* Handle case of no slots stored. */
 	if (slot_max == 0)
 		return 0;
 
-	return slots[get_random_long() % slot_max];
+	random = get_random_long() % slot_max;
+
+	for (i=0; i< slot_area_index; i++) {
+		if (random > slot_areas[i].num) {
+			random -= slot_areas[i].num;
+			continue;
+		}
+		return slot_areas[i].addr + random * CONFIG_PHYSICAL_ALIGN;
+	}
+
+	if (i == slot_area_index )
+		debug_putstr("something wrong happened in slots_fetch_random()...\n");
+	return 0;
 }
 
 static int process_e820_entry(struct e820entry *entry,
@@ -362,7 +364,7 @@ repeat:
 	goto repeat;
 }
 
-static unsigned long find_random_addr(unsigned long minimum,
+static unsigned long find_random_phy_addr(unsigned long minimum,
 				      unsigned long size)
 {
 	int i;
@@ -374,6 +376,8 @@ static unsigned long find_random_addr(unsigned long minimum,
 	/* Verify potential e820 positions, appending to slots list. */
 	for (i = 0; i < real_mode->e820_entries; i++) {
 		process_e820_entry(&real_mode->e820_map[i], minimum, size);
+		if ( slot_area_index == MAX_SLOT_AREA )
+			break;
 	}
 
 	return slots_fetch_random();
-- 
1.9.3

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