From d0b2f91bede3bd5e3d24dd6803e56eee959c1797 Mon Sep 17 00:00:00 2001 From: AndrĂ© Fabian Silva Delgado Date: Thu, 20 Oct 2016 00:10:27 -0300 Subject: Linux-libre 4.8.2-gnu --- arch/x86/boot/compressed/kaslr.c | 251 +++++++++++++++++---------------------- 1 file changed, 108 insertions(+), 143 deletions(-) (limited to 'arch/x86/boot/compressed/kaslr.c') diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c index cfeb0259e..a66854d99 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 -#include -#include - #include #include #include @@ -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(®ion, &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(®ion, &overlap)) { + store_slot_info(®ion, 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; } -- cgit v1.2.3-54-g00ecf