Option mem= will limit the max address a system can use and any memory
region above the limit will be removed.
Furthermore, memmap=nn[KMG] which has no offset specified has the same
behaviour as mem=.
KASLR needs to consider this when choosing the random position for
decompressing the kernel.
This patch implements that.
Signed-off-by: Baoquan He <b...@redhat.com>
Acked-by: Kees Cook <keesc...@chromium.org>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: x...@kernel.org
Cc: Kees Cook <keesc...@chromium.org>
Cc: Yinghai Lu <ying...@kernel.org>
Cc: Borislav Petkov <b...@suse.de>
---
arch/x86/boot/compressed/kaslr.c | 60 ++++++++++++++++++++++++++++++++--------
1 file changed, 48 insertions(+), 12 deletions(-)
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 53a06ec..e5eb0c3 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -78,6 +78,10 @@ static bool memmap_too_large;
extern unsigned long get_cmd_line_ptr(void);
+/* 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,
@@ -128,16 +132,22 @@ 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;
+ 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;
@@ -163,9 +173,14 @@ 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;
@@ -189,6 +204,7 @@ static int handle_mem_memmap(void)
size_t len = strlen((char *)args);
char *tmp_cmdline;
char *param, *val;
+ u64 mem_size;
tmp_cmdline = malloc(COMMAND_LINE_SIZE);
if (!tmp_cmdline )
@@ -211,8 +227,20 @@ 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);
@@ -449,7 +477,8 @@ 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)
@@ -463,8 +492,15 @@ 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) {
@@ -478,7 +514,7 @@ 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. */
--
2.5.5
