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Date: Thu, 7 Dec 2017 12:58:06 +0800
From: Baoquan He <bhe@...hat.com>
To: Dou Liyang <douly.fnst@...fujitsu.com>
Cc: Chao Fan <fanc.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 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.
> ...
>
> > 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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