linux-kernel - [PATCH v2 6/9] change process_e820_entry to store slot info into slot

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Date:	Mon,  2 Mar 2015 22:58:27 +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 6/9] change process_e820_entry to store slot info into slot_area

For passed in e820 entry, check if it is overlapped with avoid area.
If no just calculate and store slot info into related slot_area.
Otherwise iterate all avoid areas to find the first one, namely with
lowest starting address among all overlapped avoid areas. Then split
it by exluding that avoid area and store slot info of the preceding
part, then process the left part just as a new e820 memory region.
Repeat this till the whole e820 memory region is processed.

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 arch/x86/boot/compressed/aslr.c | 71 ++++++++++++++++++++++++++++++-----------
 1 file changed, 52 insertions(+), 19 deletions(-)

diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
index ded3959..1c6fb31 100644
--- a/arch/x86/boot/compressed/aslr.c
+++ b/arch/x86/boot/compressed/aslr.c
@@ -280,20 +280,18 @@ static unsigned long slots_fetch_random(void)
 	return slots[get_random_long() % slot_max];
 }
 
-static void process_e820_entry(struct e820entry *entry,
+static int process_e820_entry(struct e820entry *entry,
 			       unsigned long minimum,
 			       unsigned long image_size)
 {
-	struct mem_vector region, img;
+	struct mem_vector region, img, out;
+	struct slot_area slot_area;
+	unsigned long min, start_orig;
 
 	/* Skip non-RAM entries. */
 	if (entry->type != E820_RAM)
 		return;
 
-	/* Ignore entries entirely above our maximum. */
-	if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
-		return;
-
 	/* Ignore entries entirely below our minimum. */
 	if (entry->addr + entry->size < minimum)
 		return;
@@ -305,6 +303,14 @@ static void process_e820_entry(struct e820entry *entry,
 	if (region.start < minimum)
 		region.start = minimum;
 
+repeat:
+
+	/* Return if slot area array is full */
+	if ( slot_area_index == MAX_SLOT_AREA )
+		return;
+
+	start_orig = region.start;
+
 	/* Potentially raise address to meet alignment requirements. */
 	region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
 
@@ -313,20 +319,47 @@ static void process_e820_entry(struct e820entry *entry,
 		return;
 
 	/* Reduce size by any delta from the original address. */
-	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;
-
-	/* Walk each aligned slot and check for avoided areas. */
-	for (img.start = region.start, img.size = image_size ;
-	     mem_contains(&region, &img) ;
-	     img.start += CONFIG_PHYSICAL_ALIGN) {
-		if (mem_avoid_overlap(&img))
-			continue;
-		slots_append(img.start);
+	region.size -= region.start - start_orig;
+
+	if ( region.size < image_size )
+		return;
+
+	if (!mem_avoid_overlap(&region)) {
+		slot_area.addr = region.start;
+		if ( image_size <= CONFIG_PHYSICAL_ALIGN)
+			slot_area.num = region.size / CONFIG_PHYSICAL_ALIGN;
+		else
+			slot_area.num = ( region.size - image_size ) /
+				CONFIG_PHYSICAL_ALIGN + 1;
+
+		if (slot_area.num > 0) {
+			slot_areas[slot_area_index++] = slot_area;
+			slot_max += slot_area.num;
+		}
+		return;
 	}
+
+	min = mem_min_overlap(&region, &out);
+
+	if ( min > region.start + image_size ) {
+		unsigned long size = min - region.start;
+
+		slot_area.addr = region.start;
+		if ( image_size <= CONFIG_PHYSICAL_ALIGN)
+                        slot_area.num = (min - region.start ) / CONFIG_PHYSICAL_ALIGN;
+                else
+                        slot_area.num = ( min - region.start - image_size ) /
+                                CONFIG_PHYSICAL_ALIGN + 1;
+
+		if (slot_area.num > 0) {
+			slot_areas[slot_area_index++] = slot_area;
+			slot_max += slot_area.num;
+		}
+	}
+
+	region.size -= out.start - region.start + out.size;
+	region.start = out.start + out.size;
+	goto repeat;
 }
 
 static unsigned long find_random_addr(unsigned long minimum,
-- 
1.9.3

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