Re: [PATCH v3 1/4] kaslr: add immovable_mem=nn[KMG]@ss[KMG] to specify extracting memory

[Baoquan He <bhe@redhat.com>]

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@cn.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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