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Date: Thu, 7 Dec 2017 13:31:55 +0800
From: Chao Fan <fanc.fnst@...fujitsu.com>
To: Baoquan He <bhe@...hat.com>
CC: Dou Liyang <douly.fnst@...fujitsu.com>,
<linux-kernel@...r.kernel.org>, <x86@...nel.org>, <hpa@...or.com>,
<tglx@...utronix.de>, <mingo@...hat.com>, <keescook@...omium.org>,
<yasu.isimatu@...il.com>, <indou.takao@...fujitsu.com>,
<caoj.fnst@...fujitsu.com>
Subject: Re: [PATCH v3 1/4] kaslr: add immovable_mem=nn[KMG]@ss[KMG] to
specify extracting memory
On Thu, Dec 07, 2017 at 12:58:06PM +0800, Baoquan He wrote:
>On 12/07/17 at 12:16pm, Dou Liyang wrote:
>> Hi All,
>>
>> At 12/07/2017 11:56 AM, Chao Fan wrote:
>> > On Thu, Dec 07, 2017 at 11:09:24AM +0800, Baoquan He wrote:
>> > > On 12/07/17 at 10:53am, Chao Fan wrote:
>> > > > On Wed, Dec 06, 2017 at 05:35:57PM +0800, Baoquan He wrote:
>> > > > > Hi Chao,
>> > > > >
>> > > > > Yes, now the code looks much better than the last version.
>> > > > >
>> > > > > On 12/05/17 at 04:51pm, Chao Fan wrote:
>> > > > > > In current code, kaslr may choose the memory region in movable
>> > > > > > nodes to extract kernel, which will make the nodes can't be hot-removed.
>> > > > > > To solve it, we can specify the memory region in immovable node.
>> > > > > > Create immovable_mem to store the regions in immovable_mem, where should
>> > > > > > be chosen by kaslr.
>> > > > > >
>> > > > > > Multiple regions can be specified, comma delimited.
>> > > > > > Considering the usage of memory, only support for 4 regions.
>> > > > > > 4 regions contains 2 nodes at least, enough for kernel to extract.
>> > > > > >
>> > > > > > Also change the "handle_mem_memmap" to "handle_mem_filter", since
>> > > > > > it will not only handle memmap parameter now.
>> > > > >
>> > > > > One concern is whether it will fail to do KASLR if only specify
>> > > >
>> > > > Sorry, I think I have not understood your point.
>> > > > So if there is something wrong, please let me know.
>> > >
>> > > What I meant is whether we need check 'movable_node' and
>> > > 'immovable_mem=' being specified together. If only specify 'movable_node',
>> > > we may need to return and do not do kaslr or do not do physical kaslr
>> > > since kernel could be located on movable mem region.
>> >
>> Indeed.
>>
>> If *immovable_mem* is valid only when Kernel supports both
>> KASLR and Node hotplug(movable_node). we need check them together:
>>
>> ...
>> else if (!strcmp(param, "movable_node")) {
>> if (!strcmp(param, "immovable_mem"))
>> parse_immovable_mem_regions(val);
>> else
>> //no KASLR or no node hotplug?
>>
>> }
>
>Yes, I meant this. We can skip kernel physical address randomization,
>the virtual address can still be randomized.
>
Thanks Baoquan and Dou, I will make the new version.
Thanks,
Chao Fan
>> ...
>>
>> > I think both are OK and have reasons, and I tend to not return.
>> > Because if there is a parameter can solve the problem, but not specified.
>> > It's a problem of user-level.
>> > How do you think?
>> >
>>
>> Seems we should clarify the scope of 'immovable_mem=' and document it.
>>
>> Thanks,
>> dou
>>
>> > Thanks,
>> > Chao Fan
>> >
>> > >
>> > > Otherwise it will do physical kaslr anyway, memory hotplug will be
>> > > impacted later.
>> > >
>> > > >
>> > > > I don't think if only specify "movable_node" will fail KASLR.
>> > > > Since in this patchset(3/4), only disable kernel mirror. KASLR in
>> > > > current upstream code didn't parse "movable_node".
>> > > >
>> > > > > "movable_node". Surely in this case it won't fail system, just hotplug
>> > > > > memory might be impacted if kernel is located on that, will FJ mind
>> > > >
>> > > > Yes, it's the reason why I make this patchset.
>> > > > In my personal understanding, "movable_node" is a beginning why I make
>> > > > this patchset, but not the whole reason.
>> > > > Only "movable_node" specified might cause hotplug memory can't be
>> > > > removed if kernel is located on that, so we need the help of
>> > > > "immovable_mem=". "movable_node" help hotplug memory can be removed, and
>> > > > "immovable_mem=" works for the same target, but just in kaslr.
>> > > > So up to now, there is not a very tight coupling between "movable_node"
>> > > > and "immovable_mem=". The independence of "immovable_mem=" is that,
>> > > > help kaslr selects the right regions, avoid the memory in hotpluggable
>> > > > NUMA nodes, which causes the memory can't removed. It's a independent
>> > > > reason why we need a parameter like "immovable_mem=".
>> > > > So I think we should also handle it if only specify "immovable_mem="
>> > > > without "movable_node".
>> > > >
>> > > > Thanks,
>> > > > Chao Fan
>> > > >
>> > > > > this? And what if only specify 'immovable_mem=' but without 'movable_node'?
>> > > > >
>> > > > > Thanks
>> > > > > Baoquan
>> > > > >
>> > > > > >
>> > > > > > Signed-off-by: Chao Fan <fanc.fnst@...fujitsu.com>
>> > > > > > ---
>> > > > > > arch/x86/boot/compressed/kaslr.c | 80 ++++++++++++++++++++++++++++++++++++++--
>> > > > > > 1 file changed, 77 insertions(+), 3 deletions(-)
>> > > > > >
>> > > > > > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
>> > > > > > index a63fbc25ce84..0bbbaf5f6370 100644
>> > > > > > --- a/arch/x86/boot/compressed/kaslr.c
>> > > > > > +++ b/arch/x86/boot/compressed/kaslr.c
>> > > > > > @@ -108,6 +108,15 @@ enum mem_avoid_index {
>> > > > > > static struct mem_vector mem_avoid[MEM_AVOID_MAX];
>> > > > > > +/* Only supporting at most 4 immovable memory regions with kaslr */
>> > > > > > +#define MAX_IMMOVABLE_MEM 4
>> > > > > > +
>> > > > > > +/* Store the memory regions in immovable node */
>> > > > > > +static struct mem_vector immovable_mem[MAX_IMMOVABLE_MEM];
>> > > > > > +
>> > > > > > +/* The immovable regions user specify, not more than 4 */
>> > > > > > +static int num_immovable_region;
>> > > > > > +
>> > > > > > static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two)
>> > > > > > {
>> > > > > > /* Item one is entirely before item two. */
>> > > > > > @@ -168,6 +177,38 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
>> > > > > > return -EINVAL;
>> > > > > > }
>> > > > > > +static int parse_immovable_mem(char *p,
>> > > > > > + unsigned long long *start,
>> > > > > > + unsigned long long *size)
>> > > > > > +{
>> > > > > > + char *oldp;
>> > > > > > +
>> > > > > > + if (!p)
>> > > > > > + return -EINVAL;
>> > > > > > +
>> > > > > > + oldp = p;
>> > > > > > + *size = memparse(p, &p);
>> > > > > > + if (p == oldp)
>> > > > > > + return -EINVAL;
>> > > > > > +
>> > > > > > + /* We support nn[KMG]@ss[KMG] and nn[KMG]. */
>> > > > > > + switch (*p) {
>> > > > > > + case '@':
>> > > > > > + *start = memparse(p + 1, &p);
>> > > > > > + return 0;
>> > > > > > + default:
>> > > > > > + /*
>> > > > > > + * If w/o offset, only size specified, immovable_mem=nn[KMG]
>> > > > > > + * has the same behaviour as immovable_mem=nn[KMG]@0. It means
>> > > > > > + * the region starts from 0.
>> > > > > > + */
>> > > > > > + *start = 0;
>> > > > > > + return 0;
>> > > > > > + }
>> > > > > > +
>> > > > > > + return -EINVAL;
>> > > > > > +}
>> > > > > > +
>> > > > > > static void mem_avoid_memmap(char *str)
>> > > > > > {
>> > > > > > static int i;
>> > > > > > @@ -207,7 +248,37 @@ static void mem_avoid_memmap(char *str)
>> > > > > > memmap_too_large = true;
>> > > > > > }
>> > > > > > -static int handle_mem_memmap(void)
>> > > > > > +#ifdef CONFIG_MEMORY_HOTPLUG
>> > > > > > +static void parse_immovable_mem_regions(char *str)
>> > > > > > +{
>> > > > > > + static int i;
>> > > > > > +
>> > > > > > + while (str && (i < MAX_IMMOVABLE_MEM)) {
>> > > > > > + int rc;
>> > > > > > + unsigned long long start, size;
>> > > > > > + char *k = strchr(str, ',');
>> > > > > > +
>> > > > > > + if (k)
>> > > > > > + *k++ = 0;
>> > > > > > +
>> > > > > > + rc = parse_immovable_mem(str, &start, &size);
>> > > > > > + if (rc < 0)
>> > > > > > + break;
>> > > > > > + str = k;
>> > > > > > +
>> > > > > > + immovable_mem[i].start = start;
>> > > > > > + immovable_mem[i].size = size;
>> > > > > > + i++;
>> > > > > > + }
>> > > > > > + num_immovable_region = i;
>> > > > > > +}
>> > > > > > +#else
>> > > > > > +static inline void parse_immovable_mem_regions(char *str)
>> > > > > > +{
>> > > > > > +}
>> > > > > > +#endif
>> > > > > > +
>> > > > > > +static int handle_mem_filter(void)
>> > > > > > {
>> > > > > > char *args = (char *)get_cmd_line_ptr();
>> > > > > > size_t len = strlen((char *)args);
>> > > > > > @@ -215,7 +286,8 @@ 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, "immovable_mem="))
>> > > > > > return 0;
>> > > > > > tmp_cmdline = malloc(len + 1);
>> > > > > > @@ -240,6 +312,8 @@ static int handle_mem_memmap(void)
>> > > > > > if (!strcmp(param, "memmap")) {
>> > > > > > mem_avoid_memmap(val);
>> > > > > > + } else if (!strcmp(param, "immovable_mem")) {
>> > > > > > + parse_immovable_mem_regions(val);
>> > > > > > } else if (!strcmp(param, "mem")) {
>> > > > > > char *p = val;
>> > > > > > @@ -379,7 +453,7 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
>> > > > > > /* We don't need to set a mapping for setup_data. */
>> > > > > > /* Mark the memmap regions we need to avoid */
>> > > > > > - handle_mem_memmap();
>> > > > > > + handle_mem_filter();
>> > > > > > #ifdef CONFIG_X86_VERBOSE_BOOTUP
>> > > > > > /* Make sure video RAM can be used. */
>> > > > > > --
>> > > > > > 2.14.3
>> > > > > >
>> > > > > >
>> > > > > >
>> > > > >
>> > > > >
>> > > >
>> > > >
>> > >
>> > >
>> >
>>
>>
>
>
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