diff options
Diffstat (limited to 'arch/x86/boot/compressed')
| -rw-r--r-- | arch/x86/boot/compressed/Makefile | 2 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/aslr.c | 316 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/cmdline.c | 2 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/cpuflags.c | 12 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/head_32.S | 10 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/head_64.S | 16 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/misc.c | 18 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/misc.h | 37 |
8 files changed, 385 insertions, 28 deletions
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index c8a6792e7842..0fcd9133790c 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -28,7 +28,7 @@ HOST_EXTRACFLAGS += -I$(srctree)/tools/include VMLINUX_OBJS = $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \ $(obj)/string.o $(obj)/cmdline.o $(obj)/early_serial_console.o \ - $(obj)/piggy.o + $(obj)/piggy.o $(obj)/cpuflags.o $(obj)/aslr.o $(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c new file mode 100644 index 000000000000..90a21f430117 --- /dev/null +++ b/arch/x86/boot/compressed/aslr.c @@ -0,0 +1,316 @@ +#include "misc.h" + +#ifdef CONFIG_RANDOMIZE_BASE +#include <asm/msr.h> +#include <asm/archrandom.h> +#include <asm/e820.h> + +#include <generated/compile.h> +#include <linux/module.h> +#include <linux/uts.h> +#include <linux/utsname.h> +#include <generated/utsrelease.h> + +/* Simplified build-specific string for starting entropy. */ +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) +{ + size_t i; + unsigned long *ptr = (unsigned long *)area; + + for (i = 0; i < size / sizeof(hash); i++) { + /* Rotate by odd number of bits and XOR. */ + hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7); + hash ^= ptr[i]; + } + + return hash; +} + +/* Attempt to create a simple but unpredictable starting entropy. */ +static unsigned long get_random_boot(void) +{ + unsigned long hash = 0; + + hash = rotate_xor(hash, build_str, sizeof(build_str)); + hash = rotate_xor(hash, real_mode, sizeof(*real_mode)); + + return hash; +} + +static unsigned long get_random_long(void) +{ +#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("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"); + rdtscll(raw); + + 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; +} + +struct mem_vector { + unsigned long start; + unsigned long size; +}; + +#define MEM_AVOID_MAX 5 +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. */ + if (one->start + one->size <= two->start) + return false; + /* Item one is entirely after item two. */ + if (one->start >= two->start + two->size) + return false; + return true; +} + +static void mem_avoid_init(unsigned long input, unsigned long input_size, + unsigned long output, unsigned long output_size) +{ + u64 initrd_start, initrd_size; + u64 cmd_line, cmd_line_size; + unsigned long unsafe, unsafe_len; + char *ptr; + + /* + * Avoid the region that is unsafe to overlap during + * decompression (see calculations at top of misc.c). + */ + unsafe_len = (output_size >> 12) + 32768 + 18; + unsafe = (unsigned long)input + input_size - unsafe_len; + mem_avoid[0].start = unsafe; + mem_avoid[0].size = unsafe_len; + + /* Avoid initrd. */ + initrd_start = (u64)real_mode->ext_ramdisk_image << 32; + initrd_start |= real_mode->hdr.ramdisk_image; + initrd_size = (u64)real_mode->ext_ramdisk_size << 32; + initrd_size |= real_mode->hdr.ramdisk_size; + mem_avoid[1].start = initrd_start; + mem_avoid[1].size = initrd_size; + + /* Avoid kernel command line. */ + cmd_line = (u64)real_mode->ext_cmd_line_ptr << 32; + cmd_line |= real_mode->hdr.cmd_line_ptr; + /* Calculate size of cmd_line. */ + ptr = (char *)(unsigned long)cmd_line; + for (cmd_line_size = 0; ptr[cmd_line_size++]; ) + ; + mem_avoid[2].start = cmd_line; + mem_avoid[2].size = cmd_line_size; + + /* Avoid heap memory. */ + mem_avoid[3].start = (unsigned long)free_mem_ptr; + mem_avoid[3].size = BOOT_HEAP_SIZE; + + /* Avoid stack memory. */ + mem_avoid[4].start = (unsigned long)free_mem_end_ptr; + mem_avoid[4].size = BOOT_STACK_SIZE; +} + +/* Does this memory vector overlap a known avoided area? */ +bool mem_avoid_overlap(struct mem_vector *img) +{ + int i; + + for (i = 0; i < MEM_AVOID_MAX; i++) { + if (mem_overlaps(img, &mem_avoid[i])) + return true; + } + + return false; +} + +unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET / CONFIG_PHYSICAL_ALIGN]; +unsigned long slot_max = 0; + +static void slots_append(unsigned long addr) +{ + /* Overflowing the slots list should be impossible. */ + if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET / + CONFIG_PHYSICAL_ALIGN) + return; + + slots[slot_max++] = addr; +} + +static unsigned long slots_fetch_random(void) +{ + /* Handle case of no slots stored. */ + if (slot_max == 0) + return 0; + + return slots[get_random_long() % slot_max]; +} + +static void process_e820_entry(struct e820entry *entry, + unsigned long minimum, + unsigned long image_size) +{ + struct mem_vector region, img; + + /* Skip non-RAM entries. */ + if (entry->type != E820_RAM) + return; + + /* Ignore entries entirely above our maximum. */ + if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET) + return; + + /* Ignore entries entirely below our minimum. */ + if (entry->addr + entry->size < minimum) + return; + + region.start = entry->addr; + region.size = entry->size; + + /* Potentially raise address to minimum location. */ + if (region.start < minimum) + region.start = minimum; + + /* Potentially raise address to meet alignment requirements. */ + region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN); + + /* Did we raise the address above the bounds of this e820 region? */ + if (region.start > entry->addr + entry->size) + return; + + /* Reduce size by any delta from the original address. */ + region.size -= region.start - entry->addr; + + /* Reduce maximum size to fit end of image within maximum limit. */ + if (region.start + region.size > CONFIG_RANDOMIZE_BASE_MAX_OFFSET) + region.size = CONFIG_RANDOMIZE_BASE_MAX_OFFSET - region.start; + + /* 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)) + continue; + slots_append(img.start); + } +} + +static unsigned long find_random_addr(unsigned long minimum, + unsigned long size) +{ + int i; + unsigned long addr; + + /* Make sure minimum is aligned. */ + minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN); + + /* Verify potential e820 positions, appending to slots list. */ + for (i = 0; i < real_mode->e820_entries; i++) { + process_e820_entry(&real_mode->e820_map[i], minimum, size); + } + + return slots_fetch_random(); +} + +unsigned char *choose_kernel_location(unsigned char *input, + unsigned long input_size, + unsigned char *output, + unsigned long output_size) +{ + unsigned long choice = (unsigned long)output; + unsigned long random; + + if (cmdline_find_option_bool("nokaslr")) { + debug_putstr("KASLR disabled...\n"); + goto out; + } + + /* Record the various known unsafe memory ranges. */ + mem_avoid_init((unsigned long)input, input_size, + (unsigned long)output, output_size); + + /* Walk e820 and find a random address. */ + random = find_random_addr(choice, output_size); + if (!random) { + debug_putstr("KASLR could not find suitable E820 region...\n"); + goto out; + } + + /* Always enforce the minimum. */ + if (random < choice) + goto out; + + choice = random; +out: + return (unsigned char *)choice; +} + +#endif /* CONFIG_RANDOMIZE_BASE */ diff --git a/arch/x86/boot/compressed/cmdline.c b/arch/x86/boot/compressed/cmdline.c index bffd73b45b1f..b68e3033e6b9 100644 --- a/arch/x86/boot/compressed/cmdline.c +++ b/arch/x86/boot/compressed/cmdline.c @@ -1,6 +1,6 @@ #include "misc.h" -#ifdef CONFIG_EARLY_PRINTK +#if CONFIG_EARLY_PRINTK || CONFIG_RANDOMIZE_BASE static unsigned long fs; static inline void set_fs(unsigned long seg) diff --git a/arch/x86/boot/compressed/cpuflags.c b/arch/x86/boot/compressed/cpuflags.c new file mode 100644 index 000000000000..aa313466118b --- /dev/null +++ b/arch/x86/boot/compressed/cpuflags.c @@ -0,0 +1,12 @@ +#ifdef CONFIG_RANDOMIZE_BASE + +#include "../cpuflags.c" + +bool has_cpuflag(int flag) +{ + get_cpuflags(); + + return test_bit(flag, cpu.flags); +} + +#endif diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index 5d6f6891b188..9116aac232c7 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -117,9 +117,11 @@ preferred_addr: addl %eax, %ebx notl %eax andl %eax, %ebx -#else - movl $LOAD_PHYSICAL_ADDR, %ebx + cmpl $LOAD_PHYSICAL_ADDR, %ebx + jge 1f #endif + movl $LOAD_PHYSICAL_ADDR, %ebx +1: /* Target address to relocate to for decompression */ addl $z_extract_offset, %ebx @@ -191,14 +193,14 @@ relocated: leal boot_heap(%ebx), %eax pushl %eax /* heap area */ pushl %esi /* real mode pointer */ - call decompress_kernel + call decompress_kernel /* returns kernel location in %eax */ addl $24, %esp /* * Jump to the decompressed kernel. */ xorl %ebx, %ebx - jmp *%ebp + jmp *%eax /* * Stack and heap for uncompression diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index c337422b575d..c5c1ae0997e7 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -94,9 +94,11 @@ ENTRY(startup_32) addl %eax, %ebx notl %eax andl %eax, %ebx -#else - movl $LOAD_PHYSICAL_ADDR, %ebx + cmpl $LOAD_PHYSICAL_ADDR, %ebx + jge 1f #endif + movl $LOAD_PHYSICAL_ADDR, %ebx +1: /* Target address to relocate to for decompression */ addl $z_extract_offset, %ebx @@ -269,9 +271,11 @@ preferred_addr: addq %rax, %rbp notq %rax andq %rax, %rbp -#else - movq $LOAD_PHYSICAL_ADDR, %rbp + cmpq $LOAD_PHYSICAL_ADDR, %rbp + jge 1f #endif + movq $LOAD_PHYSICAL_ADDR, %rbp +1: /* Target address to relocate to for decompression */ leaq z_extract_offset(%rbp), %rbx @@ -339,13 +343,13 @@ relocated: movl $z_input_len, %ecx /* input_len */ movq %rbp, %r8 /* output target address */ movq $z_output_len, %r9 /* decompressed length */ - call decompress_kernel + call decompress_kernel /* returns kernel location in %rax */ popq %rsi /* * Jump to the decompressed kernel. */ - jmp *%rbp + jmp *%rax .code32 no_longmode: diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index 434f077d2c4d..196eaf373a06 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -112,14 +112,8 @@ struct boot_params *real_mode; /* Pointer to real-mode data */ void *memset(void *s, int c, size_t n); void *memcpy(void *dest, const void *src, size_t n); -#ifdef CONFIG_X86_64 -#define memptr long -#else -#define memptr unsigned -#endif - -static memptr free_mem_ptr; -static memptr free_mem_end_ptr; +memptr free_mem_ptr; +memptr free_mem_end_ptr; static char *vidmem; static int vidport; @@ -395,7 +389,7 @@ static void parse_elf(void *output) free(phdrs); } -asmlinkage void decompress_kernel(void *rmode, memptr heap, +asmlinkage void *decompress_kernel(void *rmode, memptr heap, unsigned char *input_data, unsigned long input_len, unsigned char *output, @@ -422,6 +416,10 @@ asmlinkage void decompress_kernel(void *rmode, memptr heap, free_mem_ptr = heap; /* Heap */ free_mem_end_ptr = heap + BOOT_HEAP_SIZE; + output = choose_kernel_location(input_data, input_len, + output, output_len); + + /* Validate memory location choices. */ if ((unsigned long)output & (MIN_KERNEL_ALIGN - 1)) error("Destination address inappropriately aligned"); #ifdef CONFIG_X86_64 @@ -441,5 +439,5 @@ asmlinkage void decompress_kernel(void *rmode, memptr heap, parse_elf(output); handle_relocations(output, output_len); debug_putstr("done.\nBooting the kernel.\n"); - return; + return output; } diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h index 674019d8e235..24e3e569a13c 100644 --- a/arch/x86/boot/compressed/misc.h +++ b/arch/x86/boot/compressed/misc.h @@ -23,7 +23,15 @@ #define BOOT_BOOT_H #include "../ctype.h" +#ifdef CONFIG_X86_64 +#define memptr long +#else +#define memptr unsigned +#endif + /* misc.c */ +extern memptr free_mem_ptr; +extern memptr free_mem_end_ptr; extern struct boot_params *real_mode; /* Pointer to real-mode data */ void __putstr(const char *s); #define error_putstr(__x) __putstr(__x) @@ -39,23 +47,40 @@ static inline void debug_putstr(const char *s) #endif -#ifdef CONFIG_EARLY_PRINTK - +#if CONFIG_EARLY_PRINTK || CONFIG_RANDOMIZE_BASE /* cmdline.c */ int cmdline_find_option(const char *option, char *buffer, int bufsize); int cmdline_find_option_bool(const char *option); +#endif -/* early_serial_console.c */ -extern int early_serial_base; -void console_init(void); +#if CONFIG_RANDOMIZE_BASE +/* aslr.c */ +unsigned char *choose_kernel_location(unsigned char *input, + unsigned long input_size, + unsigned char *output, + unsigned long output_size); +/* cpuflags.c */ +bool has_cpuflag(int flag); #else +static inline +unsigned char *choose_kernel_location(unsigned char *input, + unsigned long input_size, + unsigned char *output, + unsigned long output_size) +{ + return output; +} +#endif +#ifdef CONFIG_EARLY_PRINTK /* early_serial_console.c */ +extern int early_serial_base; +void console_init(void); +#else static const int early_serial_base; static inline void console_init(void) { } - #endif #endif |