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877 lines
23 KiB
877 lines
23 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* kaslr.c |
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* |
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* This contains the routines needed to generate a reasonable level of |
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* entropy to choose a randomized kernel base address offset in support |
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* of Kernel Address Space Layout Randomization (KASLR). Additionally |
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* handles walking the physical memory maps (and tracking memory regions |
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* to avoid) in order to select a physical memory location that can |
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* contain the entire properly aligned running kernel image. |
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* |
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*/ |
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|
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/* |
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* isspace() in linux/ctype.h is expected by next_args() to filter |
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* out "space/lf/tab". While boot/ctype.h conflicts with linux/ctype.h, |
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* since isdigit() is implemented in both of them. Hence disable it |
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* here. |
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*/ |
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#define BOOT_CTYPE_H |
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|
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#include "misc.h" |
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#include "error.h" |
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#include "../string.h" |
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|
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#include <generated/compile.h> |
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#include <linux/module.h> |
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#include <linux/uts.h> |
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#include <linux/utsname.h> |
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#include <linux/ctype.h> |
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#include <linux/efi.h> |
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#include <generated/utsrelease.h> |
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#include <asm/efi.h> |
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|
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/* Macros used by the included decompressor code below. */ |
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#define STATIC |
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#include <linux/decompress/mm.h> |
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|
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#define _SETUP |
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#include <asm/setup.h> /* For COMMAND_LINE_SIZE */ |
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#undef _SETUP |
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extern unsigned long get_cmd_line_ptr(void); |
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|
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/* Simplified build-specific string for starting entropy. */ |
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static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@" |
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LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION; |
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static unsigned long rotate_xor(unsigned long hash, const void *area, |
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size_t size) |
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{ |
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size_t i; |
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unsigned long *ptr = (unsigned long *)area; |
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|
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for (i = 0; i < size / sizeof(hash); i++) { |
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/* Rotate by odd number of bits and XOR. */ |
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hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7); |
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hash ^= ptr[i]; |
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} |
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return hash; |
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} |
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|
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/* Attempt to create a simple but unpredictable starting entropy. */ |
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static unsigned long get_boot_seed(void) |
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{ |
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unsigned long hash = 0; |
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|
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hash = rotate_xor(hash, build_str, sizeof(build_str)); |
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hash = rotate_xor(hash, boot_params, sizeof(*boot_params)); |
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return hash; |
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} |
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|
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#define KASLR_COMPRESSED_BOOT |
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#include "../../lib/kaslr.c" |
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/* Only supporting at most 4 unusable memmap regions with kaslr */ |
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#define MAX_MEMMAP_REGIONS 4 |
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|
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static bool memmap_too_large; |
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/* |
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* Store memory limit: MAXMEM on 64-bit and KERNEL_IMAGE_SIZE on 32-bit. |
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* It may be reduced by "mem=nn[KMG]" or "memmap=nn[KMG]" command line options. |
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*/ |
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static u64 mem_limit; |
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|
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/* Number of immovable memory regions */ |
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static int num_immovable_mem; |
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|
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enum mem_avoid_index { |
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MEM_AVOID_ZO_RANGE = 0, |
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MEM_AVOID_INITRD, |
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MEM_AVOID_CMDLINE, |
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MEM_AVOID_BOOTPARAMS, |
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MEM_AVOID_MEMMAP_BEGIN, |
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MEM_AVOID_MEMMAP_END = MEM_AVOID_MEMMAP_BEGIN + MAX_MEMMAP_REGIONS - 1, |
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MEM_AVOID_MAX, |
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}; |
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static struct mem_vector mem_avoid[MEM_AVOID_MAX]; |
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|
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static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two) |
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{ |
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/* Item one is entirely before item two. */ |
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if (one->start + one->size <= two->start) |
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return false; |
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/* Item one is entirely after item two. */ |
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if (one->start >= two->start + two->size) |
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return false; |
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return true; |
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} |
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char *skip_spaces(const char *str) |
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{ |
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while (isspace(*str)) |
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++str; |
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return (char *)str; |
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} |
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#include "../../../../lib/ctype.c" |
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#include "../../../../lib/cmdline.c" |
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enum parse_mode { |
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PARSE_MEMMAP, |
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PARSE_EFI, |
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}; |
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static int |
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parse_memmap(char *p, u64 *start, u64 *size, enum parse_mode mode) |
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{ |
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char *oldp; |
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if (!p) |
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return -EINVAL; |
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|
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/* We don't care about this option here */ |
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if (!strncmp(p, "exactmap", 8)) |
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return -EINVAL; |
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oldp = p; |
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*size = memparse(p, &p); |
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if (p == oldp) |
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return -EINVAL; |
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switch (*p) { |
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case '#': |
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case '$': |
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case '!': |
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*start = memparse(p + 1, &p); |
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return 0; |
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case '@': |
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if (mode == PARSE_MEMMAP) { |
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/* |
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* memmap=nn@ss specifies usable region, should |
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* be skipped |
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*/ |
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*size = 0; |
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} else { |
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u64 flags; |
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/* |
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* efi_fake_mem=nn@ss:attr the attr specifies |
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* flags that might imply a soft-reservation. |
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*/ |
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*start = memparse(p + 1, &p); |
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if (p && *p == ':') { |
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p++; |
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if (kstrtoull(p, 0, &flags) < 0) |
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*size = 0; |
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else if (flags & EFI_MEMORY_SP) |
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return 0; |
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} |
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*size = 0; |
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} |
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fallthrough; |
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default: |
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/* |
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* If w/o offset, only size specified, memmap=nn[KMG] has the |
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* same behaviour as mem=nn[KMG]. It limits the max address |
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* system can use. Region above the limit should be avoided. |
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*/ |
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*start = 0; |
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return 0; |
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} |
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return -EINVAL; |
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} |
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static void mem_avoid_memmap(enum parse_mode mode, char *str) |
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{ |
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static int i; |
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if (i >= MAX_MEMMAP_REGIONS) |
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return; |
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while (str && (i < MAX_MEMMAP_REGIONS)) { |
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int rc; |
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u64 start, size; |
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char *k = strchr(str, ','); |
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if (k) |
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*k++ = 0; |
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rc = parse_memmap(str, &start, &size, mode); |
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if (rc < 0) |
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break; |
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str = k; |
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if (start == 0) { |
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/* Store the specified memory limit if size > 0 */ |
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if (size > 0 && size < mem_limit) |
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mem_limit = size; |
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continue; |
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} |
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mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start; |
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mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size; |
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i++; |
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} |
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/* More than 4 memmaps, fail kaslr */ |
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if ((i >= MAX_MEMMAP_REGIONS) && str) |
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memmap_too_large = true; |
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} |
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|
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/* Store the number of 1GB huge pages which users specified: */ |
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static unsigned long max_gb_huge_pages; |
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static void parse_gb_huge_pages(char *param, char *val) |
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{ |
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static bool gbpage_sz; |
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char *p; |
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if (!strcmp(param, "hugepagesz")) { |
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p = val; |
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if (memparse(p, &p) != PUD_SIZE) { |
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gbpage_sz = false; |
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return; |
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} |
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if (gbpage_sz) |
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warn("Repeatedly set hugeTLB page size of 1G!\n"); |
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gbpage_sz = true; |
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return; |
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} |
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if (!strcmp(param, "hugepages") && gbpage_sz) { |
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p = val; |
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max_gb_huge_pages = simple_strtoull(p, &p, 0); |
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return; |
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} |
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} |
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static void handle_mem_options(void) |
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{ |
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char *args = (char *)get_cmd_line_ptr(); |
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size_t len; |
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char *tmp_cmdline; |
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char *param, *val; |
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u64 mem_size; |
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if (!args) |
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return; |
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len = strnlen(args, COMMAND_LINE_SIZE-1); |
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tmp_cmdline = malloc(len + 1); |
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if (!tmp_cmdline) |
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error("Failed to allocate space for tmp_cmdline"); |
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memcpy(tmp_cmdline, args, len); |
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tmp_cmdline[len] = 0; |
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args = tmp_cmdline; |
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/* Chew leading spaces */ |
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args = skip_spaces(args); |
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while (*args) { |
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args = next_arg(args, ¶m, &val); |
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/* Stop at -- */ |
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if (!val && strcmp(param, "--") == 0) |
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break; |
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if (!strcmp(param, "memmap")) { |
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mem_avoid_memmap(PARSE_MEMMAP, val); |
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} else if (IS_ENABLED(CONFIG_X86_64) && strstr(param, "hugepages")) { |
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parse_gb_huge_pages(param, val); |
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} else if (!strcmp(param, "mem")) { |
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char *p = val; |
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if (!strcmp(p, "nopentium")) |
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continue; |
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mem_size = memparse(p, &p); |
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if (mem_size == 0) |
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break; |
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if (mem_size < mem_limit) |
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mem_limit = mem_size; |
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} else if (!strcmp(param, "efi_fake_mem")) { |
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mem_avoid_memmap(PARSE_EFI, val); |
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} |
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} |
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free(tmp_cmdline); |
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return; |
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} |
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/* |
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* In theory, KASLR can put the kernel anywhere in the range of [16M, MAXMEM) |
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* on 64-bit, and [16M, KERNEL_IMAGE_SIZE) on 32-bit. |
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* |
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* The mem_avoid array is used to store the ranges that need to be avoided |
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* when KASLR searches for an appropriate random address. We must avoid any |
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* regions that are unsafe to overlap with during decompression, and other |
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* things like the initrd, cmdline and boot_params. This comment seeks to |
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* explain mem_avoid as clearly as possible since incorrect mem_avoid |
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* memory ranges lead to really hard to debug boot failures. |
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* |
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* The initrd, cmdline, and boot_params are trivial to identify for |
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* avoiding. They are MEM_AVOID_INITRD, MEM_AVOID_CMDLINE, and |
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* MEM_AVOID_BOOTPARAMS respectively below. |
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* |
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* What is not obvious how to avoid is the range of memory that is used |
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* during decompression (MEM_AVOID_ZO_RANGE below). This range must cover |
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* the compressed kernel (ZO) and its run space, which is used to extract |
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* the uncompressed kernel (VO) and relocs. |
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* |
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* ZO's full run size sits against the end of the decompression buffer, so |
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* we can calculate where text, data, bss, etc of ZO are positioned more |
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* easily. |
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* |
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* For additional background, the decompression calculations can be found |
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* in header.S, and the memory diagram is based on the one found in misc.c. |
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* |
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* The following conditions are already enforced by the image layouts and |
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* associated code: |
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* - input + input_size >= output + output_size |
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* - kernel_total_size <= init_size |
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* - kernel_total_size <= output_size (see Note below) |
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* - output + init_size >= output + output_size |
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* |
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* (Note that kernel_total_size and output_size have no fundamental |
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* relationship, but output_size is passed to choose_random_location |
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* as a maximum of the two. The diagram is showing a case where |
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* kernel_total_size is larger than output_size, but this case is |
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* handled by bumping output_size.) |
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* |
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* The above conditions can be illustrated by a diagram: |
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* |
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* 0 output input input+input_size output+init_size |
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* | | | | | |
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* | | | | | |
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* |-----|--------|--------|--------------|-----------|--|-------------| |
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* | | | |
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* | | | |
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* output+init_size-ZO_INIT_SIZE output+output_size output+kernel_total_size |
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* |
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* [output, output+init_size) is the entire memory range used for |
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* extracting the compressed image. |
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* |
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* [output, output+kernel_total_size) is the range needed for the |
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* uncompressed kernel (VO) and its run size (bss, brk, etc). |
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* |
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* [output, output+output_size) is VO plus relocs (i.e. the entire |
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* uncompressed payload contained by ZO). This is the area of the buffer |
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* written to during decompression. |
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* |
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* [output+init_size-ZO_INIT_SIZE, output+init_size) is the worst-case |
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* range of the copied ZO and decompression code. (i.e. the range |
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* covered backwards of size ZO_INIT_SIZE, starting from output+init_size.) |
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* |
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* [input, input+input_size) is the original copied compressed image (ZO) |
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* (i.e. it does not include its run size). This range must be avoided |
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* because it contains the data used for decompression. |
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* |
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* [input+input_size, output+init_size) is [_text, _end) for ZO. This |
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* range includes ZO's heap and stack, and must be avoided since it |
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* performs the decompression. |
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* |
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* Since the above two ranges need to be avoided and they are adjacent, |
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* they can be merged, resulting in: [input, output+init_size) which |
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* becomes the MEM_AVOID_ZO_RANGE below. |
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*/ |
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static void mem_avoid_init(unsigned long input, unsigned long input_size, |
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unsigned long output) |
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{ |
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unsigned long init_size = boot_params->hdr.init_size; |
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u64 initrd_start, initrd_size; |
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unsigned long cmd_line, cmd_line_size; |
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/* |
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* Avoid the region that is unsafe to overlap during |
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* decompression. |
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*/ |
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mem_avoid[MEM_AVOID_ZO_RANGE].start = input; |
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mem_avoid[MEM_AVOID_ZO_RANGE].size = (output + init_size) - input; |
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|
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/* Avoid initrd. */ |
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initrd_start = (u64)boot_params->ext_ramdisk_image << 32; |
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initrd_start |= boot_params->hdr.ramdisk_image; |
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initrd_size = (u64)boot_params->ext_ramdisk_size << 32; |
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initrd_size |= boot_params->hdr.ramdisk_size; |
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mem_avoid[MEM_AVOID_INITRD].start = initrd_start; |
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mem_avoid[MEM_AVOID_INITRD].size = initrd_size; |
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/* No need to set mapping for initrd, it will be handled in VO. */ |
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/* Avoid kernel command line. */ |
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cmd_line = get_cmd_line_ptr(); |
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/* Calculate size of cmd_line. */ |
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if (cmd_line) { |
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cmd_line_size = strnlen((char *)cmd_line, COMMAND_LINE_SIZE-1) + 1; |
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mem_avoid[MEM_AVOID_CMDLINE].start = cmd_line; |
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mem_avoid[MEM_AVOID_CMDLINE].size = cmd_line_size; |
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} |
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/* Avoid boot parameters. */ |
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mem_avoid[MEM_AVOID_BOOTPARAMS].start = (unsigned long)boot_params; |
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mem_avoid[MEM_AVOID_BOOTPARAMS].size = sizeof(*boot_params); |
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/* We don't need to set a mapping for setup_data. */ |
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/* Mark the memmap regions we need to avoid */ |
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handle_mem_options(); |
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/* Enumerate the immovable memory regions */ |
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num_immovable_mem = count_immovable_mem_regions(); |
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} |
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|
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/* |
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* Does this memory vector overlap a known avoided area? If so, record the |
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* overlap region with the lowest address. |
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*/ |
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static bool mem_avoid_overlap(struct mem_vector *img, |
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struct mem_vector *overlap) |
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{ |
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int i; |
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struct setup_data *ptr; |
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u64 earliest = img->start + img->size; |
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bool is_overlapping = false; |
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for (i = 0; i < MEM_AVOID_MAX; i++) { |
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if (mem_overlaps(img, &mem_avoid[i]) && |
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mem_avoid[i].start < earliest) { |
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*overlap = mem_avoid[i]; |
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earliest = overlap->start; |
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is_overlapping = true; |
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} |
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} |
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/* Avoid all entries in the setup_data linked list. */ |
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ptr = (struct setup_data *)(unsigned long)boot_params->hdr.setup_data; |
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while (ptr) { |
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struct mem_vector avoid; |
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avoid.start = (unsigned long)ptr; |
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avoid.size = sizeof(*ptr) + ptr->len; |
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|
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if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) { |
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*overlap = avoid; |
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earliest = overlap->start; |
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is_overlapping = true; |
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} |
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|
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if (ptr->type == SETUP_INDIRECT && |
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((struct setup_indirect *)ptr->data)->type != SETUP_INDIRECT) { |
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avoid.start = ((struct setup_indirect *)ptr->data)->addr; |
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avoid.size = ((struct setup_indirect *)ptr->data)->len; |
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|
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if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) { |
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*overlap = avoid; |
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earliest = overlap->start; |
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is_overlapping = true; |
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} |
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} |
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ptr = (struct setup_data *)(unsigned long)ptr->next; |
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} |
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return is_overlapping; |
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} |
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struct slot_area { |
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u64 addr; |
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unsigned long num; |
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}; |
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#define MAX_SLOT_AREA 100 |
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static struct slot_area slot_areas[MAX_SLOT_AREA]; |
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static unsigned int slot_area_index; |
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static unsigned long slot_max; |
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static void store_slot_info(struct mem_vector *region, unsigned long image_size) |
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{ |
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struct slot_area slot_area; |
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if (slot_area_index == MAX_SLOT_AREA) |
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return; |
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slot_area.addr = region->start; |
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slot_area.num = 1 + (region->size - image_size) / CONFIG_PHYSICAL_ALIGN; |
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slot_areas[slot_area_index++] = slot_area; |
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slot_max += slot_area.num; |
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} |
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|
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/* |
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* Skip as many 1GB huge pages as possible in the passed region |
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* according to the number which users specified: |
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*/ |
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static void |
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process_gb_huge_pages(struct mem_vector *region, unsigned long image_size) |
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{ |
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u64 pud_start, pud_end; |
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unsigned long gb_huge_pages; |
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struct mem_vector tmp; |
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if (!IS_ENABLED(CONFIG_X86_64) || !max_gb_huge_pages) { |
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store_slot_info(region, image_size); |
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return; |
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} |
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/* Are there any 1GB pages in the region? */ |
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pud_start = ALIGN(region->start, PUD_SIZE); |
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pud_end = ALIGN_DOWN(region->start + region->size, PUD_SIZE); |
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|
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/* No good 1GB huge pages found: */ |
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if (pud_start >= pud_end) { |
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store_slot_info(region, image_size); |
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return; |
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} |
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|
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/* Check if the head part of the region is usable. */ |
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if (pud_start >= region->start + image_size) { |
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tmp.start = region->start; |
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tmp.size = pud_start - region->start; |
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store_slot_info(&tmp, image_size); |
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} |
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|
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/* Skip the good 1GB pages. */ |
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gb_huge_pages = (pud_end - pud_start) >> PUD_SHIFT; |
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if (gb_huge_pages > max_gb_huge_pages) { |
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pud_end = pud_start + (max_gb_huge_pages << PUD_SHIFT); |
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max_gb_huge_pages = 0; |
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} else { |
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max_gb_huge_pages -= gb_huge_pages; |
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} |
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|
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/* Check if the tail part of the region is usable. */ |
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if (region->start + region->size >= pud_end + image_size) { |
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tmp.start = pud_end; |
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tmp.size = region->start + region->size - pud_end; |
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store_slot_info(&tmp, image_size); |
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} |
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} |
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|
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static u64 slots_fetch_random(void) |
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{ |
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unsigned long slot; |
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unsigned int i; |
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|
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/* Handle case of no slots stored. */ |
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if (slot_max == 0) |
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return 0; |
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slot = kaslr_get_random_long("Physical") % slot_max; |
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|
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for (i = 0; i < slot_area_index; i++) { |
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if (slot >= slot_areas[i].num) { |
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slot -= slot_areas[i].num; |
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continue; |
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} |
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return slot_areas[i].addr + ((u64)slot * CONFIG_PHYSICAL_ALIGN); |
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} |
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|
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if (i == slot_area_index) |
|
debug_putstr("slots_fetch_random() failed!?\n"); |
|
return 0; |
|
} |
|
|
|
static void __process_mem_region(struct mem_vector *entry, |
|
unsigned long minimum, |
|
unsigned long image_size) |
|
{ |
|
struct mem_vector region, overlap; |
|
u64 region_end; |
|
|
|
/* Enforce minimum and memory limit. */ |
|
region.start = max_t(u64, entry->start, minimum); |
|
region_end = min(entry->start + entry->size, mem_limit); |
|
|
|
/* Give up if slot area array is full. */ |
|
while (slot_area_index < MAX_SLOT_AREA) { |
|
/* Potentially raise address to meet alignment needs. */ |
|
region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN); |
|
|
|
/* Did we raise the address above the passed in memory entry? */ |
|
if (region.start > region_end) |
|
return; |
|
|
|
/* Reduce size by any delta from the original address. */ |
|
region.size = region_end - 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)) { |
|
process_gb_huge_pages(®ion, image_size); |
|
return; |
|
} |
|
|
|
/* Store beginning of region if holds at least image_size. */ |
|
if (overlap.start >= region.start + image_size) { |
|
region.size = overlap.start - region.start; |
|
process_gb_huge_pages(®ion, image_size); |
|
} |
|
|
|
/* Clip off the overlapping region and start over. */ |
|
region.start = overlap.start + overlap.size; |
|
} |
|
} |
|
|
|
static bool process_mem_region(struct mem_vector *region, |
|
unsigned long minimum, |
|
unsigned long image_size) |
|
{ |
|
int i; |
|
/* |
|
* If no immovable memory found, or MEMORY_HOTREMOVE disabled, |
|
* use @region directly. |
|
*/ |
|
if (!num_immovable_mem) { |
|
__process_mem_region(region, minimum, image_size); |
|
|
|
if (slot_area_index == MAX_SLOT_AREA) { |
|
debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n"); |
|
return 1; |
|
} |
|
return 0; |
|
} |
|
|
|
#if defined(CONFIG_MEMORY_HOTREMOVE) && defined(CONFIG_ACPI) |
|
/* |
|
* If immovable memory found, filter the intersection between |
|
* immovable memory and @region. |
|
*/ |
|
for (i = 0; i < num_immovable_mem; i++) { |
|
u64 start, end, entry_end, region_end; |
|
struct mem_vector entry; |
|
|
|
if (!mem_overlaps(region, &immovable_mem[i])) |
|
continue; |
|
|
|
start = immovable_mem[i].start; |
|
end = start + immovable_mem[i].size; |
|
region_end = region->start + region->size; |
|
|
|
entry.start = clamp(region->start, start, end); |
|
entry_end = clamp(region_end, start, end); |
|
entry.size = entry_end - entry.start; |
|
|
|
__process_mem_region(&entry, minimum, image_size); |
|
|
|
if (slot_area_index == MAX_SLOT_AREA) { |
|
debug_putstr("Aborted e820/efi memmap scan when walking immovable regions(slot_areas full)!\n"); |
|
return 1; |
|
} |
|
} |
|
#endif |
|
return 0; |
|
} |
|
|
|
#ifdef CONFIG_EFI |
|
/* |
|
* Returns true if we processed the EFI memmap, which we prefer over the E820 |
|
* table if it is available. |
|
*/ |
|
static bool |
|
process_efi_entries(unsigned long minimum, unsigned long image_size) |
|
{ |
|
struct efi_info *e = &boot_params->efi_info; |
|
bool efi_mirror_found = false; |
|
struct mem_vector region; |
|
efi_memory_desc_t *md; |
|
unsigned long pmap; |
|
char *signature; |
|
u32 nr_desc; |
|
int i; |
|
|
|
signature = (char *)&e->efi_loader_signature; |
|
if (strncmp(signature, EFI32_LOADER_SIGNATURE, 4) && |
|
strncmp(signature, EFI64_LOADER_SIGNATURE, 4)) |
|
return false; |
|
|
|
#ifdef CONFIG_X86_32 |
|
/* Can't handle data above 4GB at this time */ |
|
if (e->efi_memmap_hi) { |
|
warn("EFI memmap is above 4GB, can't be handled now on x86_32. EFI should be disabled.\n"); |
|
return false; |
|
} |
|
pmap = e->efi_memmap; |
|
#else |
|
pmap = (e->efi_memmap | ((__u64)e->efi_memmap_hi << 32)); |
|
#endif |
|
|
|
nr_desc = e->efi_memmap_size / e->efi_memdesc_size; |
|
for (i = 0; i < nr_desc; i++) { |
|
md = efi_early_memdesc_ptr(pmap, e->efi_memdesc_size, i); |
|
if (md->attribute & EFI_MEMORY_MORE_RELIABLE) { |
|
efi_mirror_found = true; |
|
break; |
|
} |
|
} |
|
|
|
for (i = 0; i < nr_desc; i++) { |
|
md = efi_early_memdesc_ptr(pmap, e->efi_memdesc_size, i); |
|
|
|
/* |
|
* Here we are more conservative in picking free memory than |
|
* the EFI spec allows: |
|
* |
|
* According to the spec, EFI_BOOT_SERVICES_{CODE|DATA} are also |
|
* free memory and thus available to place the kernel image into, |
|
* but in practice there's firmware where using that memory leads |
|
* to crashes. |
|
* |
|
* Only EFI_CONVENTIONAL_MEMORY is guaranteed to be free. |
|
*/ |
|
if (md->type != EFI_CONVENTIONAL_MEMORY) |
|
continue; |
|
|
|
if (efi_soft_reserve_enabled() && |
|
(md->attribute & EFI_MEMORY_SP)) |
|
continue; |
|
|
|
if (efi_mirror_found && |
|
!(md->attribute & EFI_MEMORY_MORE_RELIABLE)) |
|
continue; |
|
|
|
region.start = md->phys_addr; |
|
region.size = md->num_pages << EFI_PAGE_SHIFT; |
|
if (process_mem_region(®ion, minimum, image_size)) |
|
break; |
|
} |
|
return true; |
|
} |
|
#else |
|
static inline bool |
|
process_efi_entries(unsigned long minimum, unsigned long image_size) |
|
{ |
|
return false; |
|
} |
|
#endif |
|
|
|
static void process_e820_entries(unsigned long minimum, |
|
unsigned long image_size) |
|
{ |
|
int i; |
|
struct mem_vector region; |
|
struct boot_e820_entry *entry; |
|
|
|
/* Verify potential e820 positions, appending to slots list. */ |
|
for (i = 0; i < boot_params->e820_entries; i++) { |
|
entry = &boot_params->e820_table[i]; |
|
/* Skip non-RAM entries. */ |
|
if (entry->type != E820_TYPE_RAM) |
|
continue; |
|
region.start = entry->addr; |
|
region.size = entry->size; |
|
if (process_mem_region(®ion, minimum, image_size)) |
|
break; |
|
} |
|
} |
|
|
|
static unsigned long find_random_phys_addr(unsigned long minimum, |
|
unsigned long image_size) |
|
{ |
|
u64 phys_addr; |
|
|
|
/* Bail out early if it's impossible to succeed. */ |
|
if (minimum + image_size > mem_limit) |
|
return 0; |
|
|
|
/* Check if we had too many memmaps. */ |
|
if (memmap_too_large) { |
|
debug_putstr("Aborted memory entries scan (more than 4 memmap= args)!\n"); |
|
return 0; |
|
} |
|
|
|
if (!process_efi_entries(minimum, image_size)) |
|
process_e820_entries(minimum, image_size); |
|
|
|
phys_addr = slots_fetch_random(); |
|
|
|
/* Perform a final check to make sure the address is in range. */ |
|
if (phys_addr < minimum || phys_addr + image_size > mem_limit) { |
|
warn("Invalid physical address chosen!\n"); |
|
return 0; |
|
} |
|
|
|
return (unsigned long)phys_addr; |
|
} |
|
|
|
static unsigned long find_random_virt_addr(unsigned long minimum, |
|
unsigned long image_size) |
|
{ |
|
unsigned long slots, random_addr; |
|
|
|
/* |
|
* There are how many CONFIG_PHYSICAL_ALIGN-sized slots |
|
* that can hold image_size within the range of minimum to |
|
* KERNEL_IMAGE_SIZE? |
|
*/ |
|
slots = 1 + (KERNEL_IMAGE_SIZE - minimum - image_size) / CONFIG_PHYSICAL_ALIGN; |
|
|
|
random_addr = kaslr_get_random_long("Virtual") % slots; |
|
|
|
return random_addr * CONFIG_PHYSICAL_ALIGN + minimum; |
|
} |
|
|
|
/* |
|
* Since this function examines addresses much more numerically, |
|
* it takes the input and output pointers as 'unsigned long'. |
|
*/ |
|
void choose_random_location(unsigned long input, |
|
unsigned long input_size, |
|
unsigned long *output, |
|
unsigned long output_size, |
|
unsigned long *virt_addr) |
|
{ |
|
unsigned long random_addr, min_addr; |
|
|
|
if (cmdline_find_option_bool("nokaslr")) { |
|
warn("KASLR disabled: 'nokaslr' on cmdline."); |
|
return; |
|
} |
|
|
|
boot_params->hdr.loadflags |= KASLR_FLAG; |
|
|
|
if (IS_ENABLED(CONFIG_X86_32)) |
|
mem_limit = KERNEL_IMAGE_SIZE; |
|
else |
|
mem_limit = MAXMEM; |
|
|
|
/* Record the various known unsafe memory ranges. */ |
|
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); |
|
/* Make sure minimum is aligned. */ |
|
min_addr = ALIGN(min_addr, CONFIG_PHYSICAL_ALIGN); |
|
|
|
/* Walk available memory entries to find a random address. */ |
|
random_addr = find_random_phys_addr(min_addr, output_size); |
|
if (!random_addr) { |
|
warn("Physical KASLR disabled: no suitable memory region!"); |
|
} else { |
|
/* Update the new physical address location. */ |
|
if (*output != random_addr) |
|
*output = random_addr; |
|
} |
|
|
|
|
|
/* 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; |
|
}
|
|
|