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

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Date:   Fri, 4 Aug 2017 07:49:01 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Dou Liyang <douly.fnst@...fujitsu.com>,
        Chao Fan <fanc.fnst@...fujitsu.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, keescook@...omium.org,
        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

On 08/03/17 at 08:24pm, Chao Fan wrote:
> It's almost another "mem=".

Then why not using 'mem=' directly?

> 
> 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
> >
> 
>