linux-kernel - [PATCH] x86/boot/KASLR: Extend movable

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Date:   Thu, 3 Aug 2017 20:17:21 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC:     <fanc.fnst@...fujitsu.com>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <hpa@...or.com>, <keescook@...omium.org>,
        <bhe@...hat.com>, <dyoung@...hat.com>, <arnd@...db.de>,
        <dave.jiang@...el.com>, <indou.takao@...fujitsu.com>,
        <izumi.taku@...fujitsu.com>, Dou Liyang <douly.fnst@...fujitsu.com>
Subject: [PATCH] x86/boot/KASLR: Extend movable_node option for KASLR

movable_node is a boot-time switch to make hot-pluggable memory
NUMA nodes to be movable. This option is based on an assumption
that any node which the kernel resides in is defined as
un-hotpluggable. Linux can allocates memory near the kernel image
to try the best to keep the kernel away from hotpluggable memory
in the same NUMA node. So other nodes can be movable.

But, KASLR doesn't know which node is un-hotpluggable, the all
hotpluggable memory ranges is recorded in ACPI SRAT table, SRAT
is not parsed. So, KASLR may randomize the kernel in a movable
node which will be immovable.

Extend movable_node option to restrict kernel to be randomized in
immovable nodes by adding a parameter. this parameter sets up
the boundaries between the movable nodes and immovable nodes.

Reported-by: Chao Fan <fanc.fnst@...fujitsu.com>
Signed-off-by: Dou Liyang <douly.fnst@...fujitsu.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++--
 arch/x86/boot/compressed/kaslr.c                | 19 ++++++++++++++++---
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index d9c171c..44c7e33 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2305,7 +2305,8 @@
 	mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
 			reporting absolute coordinates, such as tablets
 
-	movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
+	movablecore=nn[KMG]
+			[KNL,X86,IA-64,PPC] This parameter
 			is similar to kernelcore except it specifies the
 			amount of memory used for migratable allocations.
 			If both kernelcore and movablecore is specified,
@@ -2315,12 +2316,18 @@
 			that the amount of memory usable for all allocations
 			is not too small.
 
-	movable_node	[KNL] Boot-time switch to make hotplugable memory
+	movable_node	[KNL] Boot-time switch to make hot-pluggable memory
 			NUMA nodes to be movable. This means that the memory
 			of such nodes will be usable only for movable
 			allocations which rules out almost all kernel
 			allocations. Use with caution!
 
+	movable_node=nn[KMG]
+			[KNL] Extend movable_node to work well with KASLR. This
+			parameter is the boundaries between the movable nodes
+			and immovable nodes, the memory which exceeds it will
+			be regarded as hot-pluggable.
+
 	MTD_Partition=	[MTD]
 			Format: <name>,<region-number>,<size>,<offset>
 
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 91f27ab..7e2351b 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -89,7 +89,10 @@ struct mem_vector {
 static bool memmap_too_large;
 
 
-/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
+/*
+ * Store memory limit specified by the following situations:
+ * "mem=nn[KMG]" or "memmap=nn[KMG]" or "movable_node=nn[KMG]"
+ */
 unsigned long long mem_limit = ULLONG_MAX;
 
 
@@ -212,7 +215,8 @@ static int handle_mem_memmap(void)
 	char *param, *val;
 	u64 mem_size;
 
-	if (!strstr(args, "memmap=") && !strstr(args, "mem="))
+	if (!strstr(args, "memmap=") && !strstr(args, "mem=") &&
+		!strstr(args, "movable_node="))
 		return 0;
 
 	tmp_cmdline = malloc(len + 1);
@@ -247,7 +251,16 @@ static int handle_mem_memmap(void)
 				free(tmp_cmdline);
 				return -EINVAL;
 			}
-			mem_limit = mem_size;
+			mem_limit = mem_limit > mem_size ? mem_size : mem_limit;
+		} else if (!strcmp(param, "movable_node")) {
+			char *p = val;
+
+			mem_size = memparse(p, &p);
+			if (mem_size == 0) {
+				free(tmp_cmdline);
+				return -EINVAL;
+			}
+			mem_limit = mem_limit > mem_size ? mem_size : mem_limit;
 		}
 	}
 
-- 
2.5.5