Re: [PATCH] x86/boot/KASLR: Extend movable_node option for KASLR

From: Chao Fan
Date: Thu Aug 03 2017 - 08:25:19 EST


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@xxxxxxxxxxxxxx>
>Signed-off-by: Dou Liyang <douly.fnst@xxxxxxxxxxxxxx>
>---
> 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
>