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

[Chao Fan <fanc.fnst@cn.fujitsu.com>]

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.

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
>> 
>> 
>> 
>
>