linux-kernel - Re: [PATCH v3 2/4] kaslr: calculate the memory region in immovable node

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Date:   Wed, 6 Dec 2017 17:28:00 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Chao Fan <fanc.fnst@...fujitsu.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, yasu.isimatu@...il.com,
        indou.takao@...fujitsu.com, caoj.fnst@...fujitsu.com,
        Dou Liyang <douly.fnst@...fujitsu.com>
Subject: Re: [PATCH v3 2/4] kaslr: calculate the memory region in immovable
 node

On 12/05/17 at 11:40am, Kees Cook wrote:
> On Tue, Dec 5, 2017 at 12:51 AM, Chao Fan <fanc.fnst@...fujitsu.com> wrote:
> > If there is no immovable memory region specified, go on the old code.
> > There are several conditons:
> > 1. CONFIG_MEMORY_HOTPLUG is not specified to y.
> > 2. immovable_mem= is not specified.
> >
> > Otherwise, calculate the intersecting between memmap entry and
> > immovable memory.
> 
> Instead of copy/pasting code between process_efi_entries() and
> process_e820_entries(), I'd rather that process_mem_region() is
> modified to deal with immovable regions.

If put it into process_mem_region(), one level of loop is added. How
about changing it like below. If no immovable_mem, just process the
region in process_immovable_mem(). This we don't need to touch
process_mem_region().


>From 9ae3f5ab0e2f129757495af2412bd52dcf86aa46 Mon Sep 17 00:00:00 2001
From: Baoquan He <bhe@...hat.com>
Date: Wed, 6 Dec 2017 17:24:55 +0800
Subject: [PATCH] KASLR: change code

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 arch/x86/boot/compressed/kaslr.c | 32 ++++++++++++++------------------
 1 file changed, 14 insertions(+), 18 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 13d26b859c69..73b1562a7439 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -638,13 +638,23 @@ static bool process_immovable_mem(struct mem_vector region,
 				  unsigned long long minimum,
 				  unsigned long long image_size)
 {
-	int i;
+	/* If no immovable_mem stored, use region directly */
+	if (num_immovable_region == 0) {
+		process_mem_region(&entry, minimum, image_size);
+
+		if (slot_area_index == MAX_SLOT_AREA) {
+			debug_putstr("Aborted memmap scan (slot_areas full)!\n");
+			return 1;
+		}
+
+		return 0;
+	}
 
 	/*
 	 * Walk all immovable regions, and filter the intersection
 	 * to process_mem_region.
 	 */
-	for (i = 0; i < num_immovable_region; i++) {
+	for (int i = 0; i < num_immovable_region; i++) {
 		struct mem_vector entry;
 		unsigned long long start, end, entry_end;
 
@@ -738,14 +748,7 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
 		region.start = md->phys_addr;
 		region.size = md->num_pages << EFI_PAGE_SHIFT;
 
-		/* If no immovable_mem stored, use region directly */
-		if (num_immovable_region == 0) {
-			process_mem_region(&region, minimum, image_size);
-			if (slot_area_index == MAX_SLOT_AREA) {
-				debug_putstr("Aborted memmap scan (slot_areas full)!\n");
-				break;
-			}
-		} else if (process_immovable_mem(region, minimum, image_size))
+		if (process_immovable_mem(region, minimum, image_size))
 			break;
 	}
 	return true;
@@ -774,14 +777,7 @@ static void process_e820_entries(unsigned long minimum,
 		region.start = entry->addr;
 		region.size = entry->size;
 
-		/* If no immovable_mem stored, use region directly */
-		if (num_immovable_region == 0) {
-			process_mem_region(&region, minimum, image_size);
-			if (slot_area_index == MAX_SLOT_AREA) {
-				debug_putstr("Aborted memmap scan (slot_areas full)!\n");
-				break;
-			}
-		} else if (process_immovable_mem(region, minimum, image_size))
+		if (process_immovable_mem(region, minimum, image_size))
 			break;
 	}
 }
-- 
2.5.5