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

[Dou Liyang]

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.

> +	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);