Re: [PATCH v5 3/4] x86/boot/KASLR: Walk srat tables to filter immovable memory

[Baoquan He <bhe@redhat.com>]

On 08/07/18 at 02:49pm, 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.
Just adjust the patch log a little bit, just for your reference.

If 'CONFIG_MEMORY_HOTREMOVE' specified, walk through the acpi srat memory
tables and store those immovable memory regions so that kaslr can get
where to choose for randomization.

> 
> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
> ---
>  arch/x86/boot/compressed/kaslr.c | 59 ++++++++++++++++++++++++++++++++
>  1 file changed, 59 insertions(+)
> 
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 302517929932..720878f967a3 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]" */
>  static unsigned long long mem_limit = ULLONG_MAX;
>  
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +/* Store the immovable memory regions */
> +static struct mem_vector immovable_mem[MAX_NUMNODES*2];
> +
> +/* Store the amount of immovable memory regions */
> +static int num_immovable_mem;
> +#endif
> +
>  
>  enum mem_avoid_index {
>  	MEM_AVOID_ZO_RANGE = 0,
> @@ -298,6 +307,51 @@ 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)

Can we change this function like below, passed in the immovable_mem and
the array lengty, the value of num_immovable_mem will be passed back?

static void handle_immovable_mem(char* region, int max, int *num)
{
}

Like this, you don't need patch 1/4 to make a header file, just put this
function handle_immovable_mem() into acpitb.c since it's handling acpi
tables. And its name can be get_immovable_mem().


> +{
> +	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"))
> +		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) {
> +		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++;
> +			}
> +
> +			if (i >= MAX_NUMNODES*2)
> +				break;
> +		}
> +		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 +475,11 @@ 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);
> -- 
> 2.17.1
> 
> 
>