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Diffstat (limited to 'arch/x86/boot/compressed/kaslr.c')
-rw-r--r--arch/x86/boot/compressed/kaslr.c251
1 files changed, 108 insertions, 143 deletions
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index cfeb0259ed81..a66854d99ee1 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -12,10 +12,6 @@
#include "misc.h"
#include "error.h"
-#include <asm/msr.h>
-#include <asm/archrandom.h>
-#include <asm/e820.h>
-
#include <generated/compile.h>
#include <linux/module.h>
#include <linux/uts.h>
@@ -26,26 +22,6 @@
static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@"
LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION;
-#define I8254_PORT_CONTROL 0x43
-#define I8254_PORT_COUNTER0 0x40
-#define I8254_CMD_READBACK 0xC0
-#define I8254_SELECT_COUNTER0 0x02
-#define I8254_STATUS_NOTREADY 0x40
-static inline u16 i8254(void)
-{
- u16 status, timer;
-
- do {
- outb(I8254_PORT_CONTROL,
- I8254_CMD_READBACK | I8254_SELECT_COUNTER0);
- status = inb(I8254_PORT_COUNTER0);
- timer = inb(I8254_PORT_COUNTER0);
- timer |= inb(I8254_PORT_COUNTER0) << 8;
- } while (status & I8254_STATUS_NOTREADY);
-
- return timer;
-}
-
static unsigned long rotate_xor(unsigned long hash, const void *area,
size_t size)
{
@@ -62,7 +38,7 @@ static unsigned long rotate_xor(unsigned long hash, const void *area,
}
/* Attempt to create a simple but unpredictable starting entropy. */
-static unsigned long get_random_boot(void)
+static unsigned long get_boot_seed(void)
{
unsigned long hash = 0;
@@ -72,50 +48,8 @@ static unsigned long get_random_boot(void)
return hash;
}
-static unsigned long get_random_long(const char *purpose)
-{
-#ifdef CONFIG_X86_64
- const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
-#else
- const unsigned long mix_const = 0x3f39e593UL;
-#endif
- unsigned long raw, random = get_random_boot();
- bool use_i8254 = true;
-
- debug_putstr(purpose);
- debug_putstr(" KASLR using");
-
- if (has_cpuflag(X86_FEATURE_RDRAND)) {
- debug_putstr(" RDRAND");
- if (rdrand_long(&raw)) {
- random ^= raw;
- use_i8254 = false;
- }
- }
-
- if (has_cpuflag(X86_FEATURE_TSC)) {
- debug_putstr(" RDTSC");
- raw = rdtsc();
-
- random ^= raw;
- use_i8254 = false;
- }
-
- if (use_i8254) {
- debug_putstr(" i8254");
- random ^= i8254();
- }
-
- /* Circular multiply for better bit diffusion */
- asm("mul %3"
- : "=a" (random), "=d" (raw)
- : "a" (random), "rm" (mix_const));
- random += raw;
-
- debug_putstr("...\n");
-
- return random;
-}
+#define KASLR_COMPRESSED_BOOT
+#include "../../lib/kaslr.c"
struct mem_vector {
unsigned long start;
@@ -132,17 +66,6 @@ enum mem_avoid_index {
static struct mem_vector mem_avoid[MEM_AVOID_MAX];
-static bool mem_contains(struct mem_vector *region, struct mem_vector *item)
-{
- /* Item at least partially before region. */
- if (item->start < region->start)
- return false;
- /* Item at least partially after region. */
- if (item->start + item->size > region->start + region->size)
- return false;
- return true;
-}
-
static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two)
{
/* Item one is entirely before item two. */
@@ -296,6 +219,7 @@ static bool mem_avoid_overlap(struct mem_vector *img,
if (mem_overlaps(img, &mem_avoid[i]) &&
mem_avoid[i].start < earliest) {
*overlap = mem_avoid[i];
+ earliest = overlap->start;
is_overlapping = true;
}
}
@@ -310,6 +234,7 @@ static bool mem_avoid_overlap(struct mem_vector *img,
if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) {
*overlap = avoid;
+ earliest = overlap->start;
is_overlapping = true;
}
@@ -319,8 +244,6 @@ static bool mem_avoid_overlap(struct mem_vector *img,
return is_overlapping;
}
-static unsigned long slots[KERNEL_IMAGE_SIZE / CONFIG_PHYSICAL_ALIGN];
-
struct slot_area {
unsigned long addr;
int num;
@@ -351,36 +274,44 @@ static void store_slot_info(struct mem_vector *region, unsigned long image_size)
}
}
-static void slots_append(unsigned long addr)
-{
- /* Overflowing the slots list should be impossible. */
- if (slot_max >= KERNEL_IMAGE_SIZE / CONFIG_PHYSICAL_ALIGN)
- return;
-
- slots[slot_max++] = addr;
-}
-
static unsigned long slots_fetch_random(void)
{
+ unsigned long slot;
+ int i;
+
/* Handle case of no slots stored. */
if (slot_max == 0)
return 0;
- return slots[get_random_long("Physical") % slot_max];
+ slot = kaslr_get_random_long("Physical") % slot_max;
+
+ for (i = 0; i < slot_area_index; i++) {
+ if (slot >= slot_areas[i].num) {
+ slot -= slot_areas[i].num;
+ continue;
+ }
+ return slot_areas[i].addr + slot * CONFIG_PHYSICAL_ALIGN;
+ }
+
+ if (i == slot_area_index)
+ debug_putstr("slots_fetch_random() failed!?\n");
+ return 0;
}
static void process_e820_entry(struct e820entry *entry,
unsigned long minimum,
unsigned long image_size)
{
- struct mem_vector region, img, overlap;
+ struct mem_vector region, overlap;
+ struct slot_area slot_area;
+ unsigned long start_orig;
/* Skip non-RAM entries. */
if (entry->type != E820_RAM)
return;
- /* Ignore entries entirely above our maximum. */
- if (entry->addr >= KERNEL_IMAGE_SIZE)
+ /* On 32-bit, ignore entries entirely above our maximum. */
+ if (IS_ENABLED(CONFIG_X86_32) && entry->addr >= KERNEL_IMAGE_SIZE)
return;
/* Ignore entries entirely below our minimum. */
@@ -390,31 +321,55 @@ static void process_e820_entry(struct e820entry *entry,
region.start = entry->addr;
region.size = entry->size;
- /* Potentially raise address to minimum location. */
- if (region.start < minimum)
- region.start = minimum;
+ /* Give up if slot area array is full. */
+ while (slot_area_index < MAX_SLOT_AREA) {
+ start_orig = region.start;
- /* Potentially raise address to meet alignment requirements. */
- region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
+ /* Potentially raise address to minimum location. */
+ if (region.start < minimum)
+ region.start = minimum;
- /* Did we raise the address above the bounds of this e820 region? */
- if (region.start > entry->addr + entry->size)
- return;
+ /* Potentially raise address to meet alignment needs. */
+ region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
- /* Reduce size by any delta from the original address. */
- region.size -= region.start - entry->addr;
+ /* Did we raise the address above this e820 region? */
+ if (region.start > entry->addr + entry->size)
+ return;
- /* Reduce maximum size to fit end of image within maximum limit. */
- if (region.start + region.size > KERNEL_IMAGE_SIZE)
- region.size = KERNEL_IMAGE_SIZE - region.start;
+ /* Reduce size by any delta from the original address. */
+ region.size -= region.start - start_orig;
- /* Walk each aligned slot and check for avoided areas. */
- for (img.start = region.start, img.size = image_size ;
- mem_contains(&region, &img) ;
- img.start += CONFIG_PHYSICAL_ALIGN) {
- if (mem_avoid_overlap(&img, &overlap))
- continue;
- slots_append(img.start);
+ /* On 32-bit, reduce region size to fit within max size. */
+ if (IS_ENABLED(CONFIG_X86_32) &&
+ region.start + region.size > KERNEL_IMAGE_SIZE)
+ region.size = KERNEL_IMAGE_SIZE - region.start;
+
+ /* Return if region can't contain decompressed kernel */
+ if (region.size < image_size)
+ return;
+
+ /* If nothing overlaps, store the region and return. */
+ if (!mem_avoid_overlap(&region, &overlap)) {
+ store_slot_info(&region, image_size);
+ return;
+ }
+
+ /* Store beginning of region if holds at least image_size. */
+ if (overlap.start > region.start + image_size) {
+ struct mem_vector beginning;
+
+ beginning.start = region.start;
+ beginning.size = overlap.start - region.start;
+ store_slot_info(&beginning, image_size);
+ }
+
+ /* Return if overlap extends to or past end of region. */
+ if (overlap.start + overlap.size >= region.start + region.size)
+ return;
+
+ /* Clip off the overlapping region and start over. */
+ region.size -= overlap.start - region.start + overlap.size;
+ region.start = overlap.start + overlap.size;
}
}
@@ -431,6 +386,10 @@ static unsigned long find_random_phys_addr(unsigned long minimum,
for (i = 0; i < boot_params->e820_entries; i++) {
process_e820_entry(&boot_params->e820_map[i], minimum,
image_size);
+ if (slot_area_index == MAX_SLOT_AREA) {
+ debug_putstr("Aborted e820 scan (slot_areas full)!\n");
+ break;
+ }
}
return slots_fetch_random();
@@ -454,7 +413,7 @@ static unsigned long find_random_virt_addr(unsigned long minimum,
slots = (KERNEL_IMAGE_SIZE - minimum - image_size) /
CONFIG_PHYSICAL_ALIGN + 1;
- random_addr = get_random_long("Virtual") % slots;
+ random_addr = kaslr_get_random_long("Virtual") % slots;
return random_addr * CONFIG_PHYSICAL_ALIGN + minimum;
}
@@ -463,48 +422,54 @@ static unsigned long find_random_virt_addr(unsigned long minimum,
* Since this function examines addresses much more numerically,
* it takes the input and output pointers as 'unsigned long'.
*/
-unsigned char *choose_random_location(unsigned long input,
- unsigned long input_size,
- unsigned long output,
- unsigned long output_size)
+void choose_random_location(unsigned long input,
+ unsigned long input_size,
+ unsigned long *output,
+ unsigned long output_size,
+ unsigned long *virt_addr)
{
- unsigned long choice = output;
- unsigned long random_addr;
+ unsigned long random_addr, min_addr;
+
+ /* By default, keep output position unchanged. */
+ *virt_addr = *output;
-#ifdef CONFIG_HIBERNATION
- if (!cmdline_find_option_bool("kaslr")) {
- warn("KASLR disabled: 'kaslr' not on cmdline (hibernation selected).");
- goto out;
- }
-#else
if (cmdline_find_option_bool("nokaslr")) {
warn("KASLR disabled: 'nokaslr' on cmdline.");
- goto out;
+ return;
}
-#endif
boot_params->hdr.loadflags |= KASLR_FLAG;
+ /* Prepare to add new identity pagetables on demand. */
+ initialize_identity_maps();
+
/* Record the various known unsafe memory ranges. */
- mem_avoid_init(input, input_size, output);
+ mem_avoid_init(input, input_size, *output);
+
+ /*
+ * Low end of the randomization range should be the
+ * smaller of 512M or the initial kernel image
+ * location:
+ */
+ min_addr = min(*output, 512UL << 20);
/* Walk e820 and find a random address. */
- random_addr = find_random_phys_addr(output, output_size);
+ random_addr = find_random_phys_addr(min_addr, output_size);
if (!random_addr) {
warn("KASLR disabled: could not find suitable E820 region!");
- goto out;
+ } else {
+ /* Update the new physical address location. */
+ if (*output != random_addr) {
+ add_identity_map(random_addr, output_size);
+ *output = random_addr;
+ }
}
- /* Always enforce the minimum. */
- if (random_addr < choice)
- goto out;
-
- choice = random_addr;
-
- add_identity_map(choice, output_size);
-
/* This actually loads the identity pagetable on x86_64. */
finalize_identity_maps();
-out:
- return (unsigned char *)choice;
+
+ /* Pick random virtual address starting from LOAD_PHYSICAL_ADDR. */
+ if (IS_ENABLED(CONFIG_X86_64))
+ random_addr = find_random_virt_addr(LOAD_PHYSICAL_ADDR, output_size);
+ *virt_addr = random_addr;
}
generated by cgit v1.2.3 (git 2.39.0) at 2024-12-04 12:10:49 +0300