Re: [PATCH v4 3/4] x86/boot/KASLR: Walk srat tables to filter immovable memory

[Chao Fan]

On Thu, Aug 02, 2018 at 11:47:13AM +0800, Dou Liyang wrote:
>Hi Fan,
>
>At 07/23/2018 05:29 PM, Chao Fan wrote:
>> If 'CONFIG_MEMORY_HOTREMOVE' specified, walk the acpi srat memory
>> tables, store the immovable memory regions, so that kaslr can get
>> the information abouth where can be selected or not.
>> If 'CONFIG_MEMORY_HOTREMOVE' not specified, go on the old code.
>> 
>> Signed-off-by: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
>> ---
>>   arch/x86/boot/compressed/kaslr.c | 55 ++++++++++++++++++++++++++++++++
>>   1 file changed, 55 insertions(+)
>> 
>> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
>> index 531c9876f573..4705682caf1f 100644
>> --- a/arch/x86/boot/compressed/kaslr.c
>> +++ b/arch/x86/boot/compressed/kaslr.c
>> @@ -31,6 +31,7 @@
>>   #include "misc.h"
>>   #include "error.h"
>> +#include "acpitb.h"
>>   #include "../string.h"
>>   #include <generated/compile.h>
>> @@ -104,6 +105,14 @@ static bool memmap_too_large;
>>   /* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
>>   unsigned long long mem_limit = ULLONG_MAX;
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +/* Store the immovable memory regions */
>> +struct mem_vector immovable_mem[];
>> +
>> +/* Store the amount of immovable memory regions */
>> +static int num_immovable_mem;
>> +#endif
>> +
>>   enum mem_avoid_index {
>>   	MEM_AVOID_ZO_RANGE = 0,
>> @@ -298,6 +307,47 @@ static int handle_mem_options(void)
>>   	return 0;
>>   }
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +/*
>> + * According to ACPI table, filter the immvoable memory regions
>> + * and store them in immovable_mem[].
>> + */
>> +static void handle_immovable_mem(void)
>> +{
>> +	struct acpi_table_header *table_header;
>> +	struct acpi_subtable_header *table;
>> +	struct acpi_srat_mem_affinity *ma;
>> +	unsigned long table_size;
>> +	unsigned long table_end;
>> +	int i = 0;
>> +
>> +	table_header = get_acpi_srat_table();
>> +
>> +	if (!table_header)
>> +		return;
>> +
>> +	table_end = (unsigned long)table_header + table_header->length;
>> +
>> +	table = (struct acpi_subtable_header *)
>> +		((unsigned long)table_header + sizeof(struct acpi_table_srat));
>> +
>> +	table_size = sizeof(struct acpi_subtable_header);
>
>table_size isn't used, can be remove.
>

Thank you very much, will update in next version.

Thanks,
Chao Fan

>> +	while (((unsigned long)table) + table->length < table_end) {
>> +		if (table->type == 1) {
>> +			ma = (struct acpi_srat_mem_affinity *)table;
>> +			if (!(ma->flags & ACPI_SRAT_MEM_HOT_PLUGGABLE)) {
>> +				immovable_mem[i].start = ma->base_address;
>> +				immovable_mem[i].size = ma->length;
>> +				i++;
>
>need a check(i < MAX_NUMNODES*2) before doing that in case of
>__IndexOutOfBoundsException__ even if it may be impossible in ACPI.
>
>Thanks,
>	dou
>> +			}
>> +		}
>> +		table = (struct acpi_subtable_header *)
>> +			((unsigned long)table + table->length);
>> +	}
>> +	num_immovable_mem = i;
>> +}
>> +#endif
>> +
>>   /*
>>    * In theory, KASLR can put the kernel anywhere in the range of [16M, 64T).
>>    * The mem_avoid array is used to store the ranges that need to be avoided
>> @@ -421,6 +471,11 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
>>   	/* Mark the memmap regions we need to avoid */
>>   	handle_mem_options();
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +	/* Mark the immovable regions we need to choose */
>> +	handle_immovable_mem();
>> +#endif
>> +
>>   #ifdef CONFIG_X86_VERBOSE_BOOTUP
>>   	/* Make sure video RAM can be used. */
>>   	add_identity_map(0, PMD_SIZE);
>>