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

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Date:   Thu, 3 Aug 2017 20:24:59 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Dou Liyang <douly.fnst@...fujitsu.com>
CC:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        <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>
Subject: Re: [PATCH] x86/boot/KASLR: Extend movable_node option for KASLR

It's almost another "mem=".

Thanks,
Chao Fan

On Thu, Aug 03, 2017 at 08:17:21PM +0800, Dou Liyang wrote:
>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
>