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Commit 4cdba14f authored by Baoquan He's avatar Baoquan He Committed by Ingo Molnar
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x86/KASLR: Handle the memory limit specified by the 'memmap=' and 'mem=' boot options 



The 'mem=' boot option limits the max address a system can use - any memory
region above the limit will be removed.

Furthermore, the 'memmap=nn[KMG]' variant (with no offset specified) has the same
behaviour as 'mem='.

KASLR needs to consider this when choosing the random position for
decompressing the kernel. Do it.

Tested-by: default avatarMasayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Signed-off-by: default avatarBaoquan He <bhe@redhat.com>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dan.j.williams@intel.com
Cc: douly.fnst@cn.fujitsu.com
Cc: dyoung@redhat.com
Link: http://lkml.kernel.org/r/1494654390-23861-3-git-send-email-bhe@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent d52e7d5a

arch/x86/boot/compressed/kaslr.c

+50 −18
Original line number Diff line number Diff line
@@ -88,6 +88,10 @@ struct mem_vector { 
static bool memmap_too_large;





/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */

unsigned long long mem_limit = ULLONG_MAX;





enum mem_avoid_index {

	MEM_AVOID_ZO_RANGE = 0,

	MEM_AVOID_INITRD,
@@ -138,16 +142,23 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size) 
		return -EINVAL;



	switch (*p) {

	case '@':

		/* Skip this region, usable */

		*start = 0;

		*size = 0;

		return 0;

	case '#':

	case '$':

	case '!':

		*start = memparse(p + 1, &p);

		return 0;

	case '@':

		/* memmap=nn@ss specifies usable region, should be skipped */

		*size = 0;

		/* Fall through */

	default:

		/*

		 * If w/o offset, only size specified, memmap=nn[KMG] has the

		 * same behaviour as mem=nn[KMG]. It limits the max address

		 * system can use. Region above the limit should be avoided.

		 */

		*start = 0;

		return 0;

	}



	return -EINVAL;
@@ -173,9 +184,14 @@ static void mem_avoid_memmap(char *str) 
		if (rc < 0)

			break;

		str = k;

		/* A usable region that should not be skipped */

		if (size == 0)



		if (start == 0) {

			/* Store the specified memory limit if size > 0 */

			if (size > 0)

				mem_limit = size;



			continue;

		}



		mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start;

		mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
@@ -187,19 +203,15 @@ static void mem_avoid_memmap(char *str) 
		memmap_too_large = true;

}





/*

 * handle_mem_memmap will also cover 'mem=' issue in next patch. Will remove

 * this note later.

 */

static int handle_mem_memmap(void)

{

	char *args = (char *)get_cmd_line_ptr();

	size_t len = strlen((char *)args);

	char *tmp_cmdline;

	char *param, *val;

	u64 mem_size;



	if (!strstr(args, "memmap="))

	if (!strstr(args, "memmap=") && !strstr(args, "mem="))

		return 0;



	tmp_cmdline = malloc(len + 1);
@@ -222,8 +234,20 @@ static int handle_mem_memmap(void) 
			return -1;

		}



		if (!strcmp(param, "memmap"))

		if (!strcmp(param, "memmap")) {

			mem_avoid_memmap(val);

		} else if (!strcmp(param, "mem")) {

			char *p = val;



			if (!strcmp(p, "nopentium"))

				continue;

			mem_size = memparse(p, &p);

			if (mem_size == 0) {

				free(tmp_cmdline);

				return -EINVAL;

			}

			mem_limit = mem_size;

		}

	}



	free(tmp_cmdline);
@@ -460,7 +484,8 @@ static void process_e820_entry(struct boot_e820_entry *entry, 
{

	struct mem_vector region, overlap;

	struct slot_area slot_area;

	unsigned long start_orig;

	unsigned long start_orig, end;

	struct boot_e820_entry cur_entry;



	/* Skip non-RAM entries. */

	if (entry->type != E820_TYPE_RAM)
@@ -474,8 +499,15 @@ static void process_e820_entry(struct boot_e820_entry *entry, 
	if (entry->addr + entry->size < minimum)

		return;



	region.start = entry->addr;

	region.size = entry->size;

	/* Ignore entries above memory limit */

	end = min(entry->size + entry->addr, mem_limit);

	if (entry->addr >= end)

		return;

	cur_entry.addr = entry->addr;

	cur_entry.size = end - entry->addr;



	region.start = cur_entry.addr;

	region.size = cur_entry.size;



	/* Give up if slot area array is full. */

	while (slot_area_index < MAX_SLOT_AREA) {
@@ -489,7 +521,7 @@ static void process_e820_entry(struct boot_e820_entry *entry, 
		region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);



		/* Did we raise the address above this e820 region? */

		if (region.start > entry->addr + entry->size)

		if (region.start > cur_entry.addr + cur_entry.size)

			return;



		/* Reduce size by any delta from the original address. */