linux-kernel - [PATCH v3 07/21] x86/kaslr: Eliminate start_orig from __process_mem

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Date:   Tue, 28 Jul 2020 18:57:08 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Kees Cook <keescook@...omium.org>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH v3 07/21] x86/kaslr: Eliminate start_orig from __process_mem_region

Set the region.size within the loop, which removes the need for
start_orig.

Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
---
 arch/x86/boot/compressed/kaslr.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index f2454eef5790..e978c3508814 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -623,7 +623,7 @@ static void __process_mem_region(struct mem_vector *entry,
 				 unsigned long image_size)
 {
 	struct mem_vector region, overlap;
-	unsigned long start_orig, end;
+	unsigned long end;
 
 	/* Ignore entries entirely below our minimum. */
 	if (entry->start + entry->size < minimum)
@@ -635,12 +635,9 @@ static void __process_mem_region(struct mem_vector *entry,
 		return;
 
 	region.start = entry->start;
-	region.size = end - entry->start;
 
 	/* Give up if slot area array is full. */
 	while (slot_area_index < MAX_SLOT_AREA) {
-		start_orig = region.start;
-
 		/* Potentially raise address to minimum location. */
 		if (region.start < minimum)
 			region.start = minimum;
@@ -653,7 +650,7 @@ static void __process_mem_region(struct mem_vector *entry,
 			return;
 
 		/* Reduce size by any delta from the original address. */
-		region.size -= region.start - start_orig;
+		region.size = end - region.start;
 
 		/* Return if region can't contain decompressed kernel */
 		if (region.size < image_size)
@@ -679,7 +676,6 @@ static void __process_mem_region(struct mem_vector *entry,
 			return;
 
 		/* Clip off the overlapping region and start over. */
-		region.size -= overlap.start - region.start + overlap.size;
 		region.start = overlap.start + overlap.size;
 	}
 }
-- 
2.26.2