Re: [PATCH v8 1/3] x86/boot: Add acpitb.c to parse acpi tables

[Chao Fan]

On Mon, Oct 15, 2018 at 04:26:09PM -0400, Masayoshi Mizuma wrote:
>Hi Chao,
>
>Let me add some suggestions.

Thanks for your review and suggestion.
I will change them in next version.

Thanks,
Chao Fan

>
>On Wed, Oct 10, 2018 at 04:41:17PM +0800, Chao Fan wrote:
>> There is a bug that kaslr may randomly chooses some positions
>> which are located in movable memory regions. This will break memory
>> hotplug feature and make the movable memory chosen by KASLR can't be
>> removed. So dig SRAT table from ACPI tables to get memory information.
>> 
>> Imitate the ACPI code of parsing ACPI tables to dig and read ACPI
>> tables. Since some operations are not needed here, functions are
>> simplified. Functions will be used to dig only SRAT tables to get
>> information of memory, so that KASLR can the memory in immovable node.
>> 
>> And also, these functions won't influence the initialization of
>> ACPI after start_kernel().
>> 
>> Since use physical address directely, so acpi_os_map_memory()
>> and acpi_os_unmap_memory() are not needed.
>> 
>> Signed-off-by: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
>> ---
>>  arch/x86/boot/compressed/Makefile |   2 +
>>  arch/x86/boot/compressed/acpitb.c | 405 ++++++++++++++++++++++++++++++
>>  arch/x86/boot/compressed/misc.h   |   8 +
>>  3 files changed, 415 insertions(+)
>>  create mode 100644 arch/x86/boot/compressed/acpitb.c
>> 
>...cut...
>> +static struct acpi_table_header *get_acpi_srat_table(void)
>> +{
>> +	char *args = (char *)get_cmd_line_ptr();
>> +	acpi_physical_address acpi_table;
>> +	acpi_physical_address root_table;
>> +	struct acpi_table_header *header;
>> +	struct acpi_table_rsdp *rsdp;
>> +	char *signature;
>> +	u8 *entry;
>> +	u32 count;
>> +	u32 size;
>> +	int i, j;
>> +	u32 len;
>> +
>> +	rsdp = (struct acpi_table_rsdp *)get_rsdp_addr();
>> +	if (!rsdp)
>> +		return NULL;
>> +
>> +	/* Get rsdt or xsdt from rsdp. */
>> +	if (!strstr(args, "acpi=rsdt") &&
>> +	    rsdp->xsdt_physical_address && rsdp->revision > 1) {
>> +		root_table = rsdp->xsdt_physical_address;
>> +		size = ACPI_XSDT_ENTRY_SIZE;
>> +	} else {
>> +		root_table = rsdp->rsdt_physical_address;
>> +		size = ACPI_RSDT_ENTRY_SIZE;
>> +	}
>> +
>> +	/* Get ACPI root table from rsdt or xsdt.*/
>> +	header = (struct acpi_table_header *)root_table;
>> +	len = header->length;
>> +	count = (u32)((len - sizeof(struct acpi_table_header)) / size);
>> +	entry = ACPI_ADD_PTR(u8, header, sizeof(struct acpi_table_header));
>> +
>> +	for (i = 0; i < count; i++) {
>> +		u64 address64;
>> +
>> +		if (size == ACPI_RSDT_ENTRY_SIZE)
>> +			acpi_table = ((acpi_physical_address)
>> +				      (*ACPI_CAST_PTR(u32, entry)));
>> +		else {
>> +			*(u64 *)(void *)&address64 = *(u64 *)(void *)entry;
>> +			acpi_table = (acpi_physical_address) address64;
>> +		}
>> +
>> +		if (acpi_table) {
>> +			header = (struct acpi_table_header *)acpi_table;
>
>> +			signature = header->signature;
>> +
>> +			if (!strncmp(signature, "SRAT", 4))
>
>			if (ACPI_COMPARE_NAME(header->signature, ACPI_SIG_SRAT))
>
>> +				return header;
>> +		}
>> +		entry += size;
>> +	}
>> +	return NULL;
>> +}
>> +
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +/*
>> + * According to ACPI table, filter the immvoable memory regions
>> + * and store them in immovable_mem[].
>> + */
>> +void get_immovable_mem(void)
>> +{
>> +	char *args = (char *)get_cmd_line_ptr();
>> +	struct acpi_table_header *table_header;
>> +	struct acpi_subtable_header *table;
>> +	struct acpi_srat_mem_affinity *ma;
>> +	unsigned long table_end;
>> +	int i = 0;
>> +
>> +	if (!strstr(args, "movable_node") || strstr(args, "acpi=off"))
>> +		return;
>> +
>> +	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));
>> +
>
>> +	while (((unsigned long)table) + table->length < table_end) {
>
>	while (((unsigned long)table) +
>			sizeof(struct acpi_subtable_header) < table_end) {
>
>> +		if (table->type == 1) {
>
>		if (table->type == ACPI_SRAT_TYPE_MEMORY_AFFINITY) {
>
>> +			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++;
>> +			}
>> +
>> +			if (i >= MAX_NUMNODES*2)
>> +				break;
>> +		}
>> +		table = (struct acpi_subtable_header *)
>> +			((unsigned long)table + table->length);
>> +	}
>> +	num_immovable_mem = i;
>> +}
>
>Thanks,
>Masa
>
>