| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Baoquan He | 1312 | 37.88% | 14 | 23.73% |
| Kees Cook | 1228 | 35.45% | 20 | 33.90% |
| Dave Jiang | 277 | 8.00% | 1 | 1.69% |
| Chao Fan | 229 | 6.61% | 2 | 3.39% |
| Dan J Williams | 128 | 3.70% | 2 | 3.39% |
| Daniel Kiper | 94 | 2.71% | 1 | 1.69% |
| Naoya Horiguchi | 59 | 1.70% | 1 | 1.69% |
| Kirill A. Shutemov | 49 | 1.41% | 5 | 8.47% |
| Yinghai Lu | 41 | 1.18% | 2 | 3.39% |
| Borislav Petkov | 22 | 0.64% | 3 | 5.08% |
| Thomas Garnier | 9 | 0.26% | 1 | 1.69% |
| Dave Hansen | 8 | 0.23% | 1 | 1.69% |
| Louis Taylor | 2 | 0.06% | 1 | 1.69% |
| Gustavo A. R. Silva | 2 | 0.06% | 1 | 1.69% |
| zhong jiang | 1 | 0.03% | 1 | 1.69% |
| Arnd Bergmann | 1 | 0.03% | 1 | 1.69% |
| Ingo Molnar | 1 | 0.03% | 1 | 1.69% |
| Greg Kroah-Hartman | 1 | 0.03% | 1 | 1.69% |
| Total | 3464 | 59 |
// SPDX-License-Identifier: GPL-2.0 /* * kaslr.c * * This contains the routines needed to generate a reasonable level of * entropy to choose a randomized kernel base address offset in support * of Kernel Address Space Layout Randomization (KASLR). Additionally * handles walking the physical memory maps (and tracking memory regions * to avoid) in order to select a physical memory location that can * contain the entire properly aligned running kernel image. * */ /* * isspace() in linux/ctype.h is expected by next_args() to filter * out "space/lf/tab". While boot/ctype.h conflicts with linux/ctype.h, * since isdigit() is implemented in both of them. Hence disable it * here. */ #define BOOT_CTYPE_H #include "misc.h" #include "error.h" #include "../string.h" #include <generated/compile.h> #include <linux/module.h> #include <linux/uts.h> #include <linux/utsname.h> #include <linux/ctype.h> #include <linux/efi.h> #include <generated/utsrelease.h> #include <asm/efi.h> /* Macros used by the included decompressor code below. */ #define STATIC #include <linux/decompress/mm.h> #ifdef CONFIG_X86_5LEVEL unsigned int __pgtable_l5_enabled; unsigned int pgdir_shift __ro_after_init = 39; unsigned int ptrs_per_p4d __ro_after_init = 1; #endif extern unsigned long get_cmd_line_ptr(void); /* Used by PAGE_KERN* macros: */ pteval_t __default_kernel_pte_mask __read_mostly = ~0; /* Simplified build-specific string for starting entropy. */ static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@" LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION; 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_boot_seed(void) { unsigned long hash = 0; hash = rotate_xor(hash, build_str, sizeof(build_str)); hash = rotate_xor(hash, boot_params, sizeof(*boot_params)); return hash; } #define KASLR_COMPRESSED_BOOT #include "../../lib/kaslr.c" /* Only supporting at most 4 unusable memmap regions with kaslr */ #define MAX_MEMMAP_REGIONS 4 static bool memmap_too_large; /* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */ static unsigned long long mem_limit = ULLONG_MAX; /* Number of immovable memory regions */ static int num_immovable_mem; enum mem_avoid_index { MEM_AVOID_ZO_RANGE = 0, MEM_AVOID_INITRD, MEM_AVOID_CMDLINE, MEM_AVOID_BOOTPARAMS, MEM_AVOID_MEMMAP_BEGIN, MEM_AVOID_MEMMAP_END = MEM_AVOID_MEMMAP_BEGIN + MAX_MEMMAP_REGIONS - 1, MEM_AVOID_MAX, }; static struct mem_vector mem_avoid[MEM_AVOID_MAX]; 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; } char *skip_spaces(const char *str) { while (isspace(*str)) ++str; return (char *)str; } #include "../../../../lib/ctype.c" #include "../../../../lib/cmdline.c" enum parse_mode { PARSE_MEMMAP, PARSE_EFI, }; static int parse_memmap(char *p, unsigned long long *start, unsigned long long *size, enum parse_mode mode) { char *oldp; if (!p) return -EINVAL; /* We don't care about this option here */ if (!strncmp(p, "exactmap", 8)) return -EINVAL; oldp = p; *size = memparse(p, &p); if (p == oldp) return -EINVAL; switch (*p) { case '#': case '$': case '!': *start = memparse(p + 1, &p); return 0; case '@': if (mode == PARSE_MEMMAP) { /* * memmap=nn@ss specifies usable region, should * be skipped */ *size = 0; } else { unsigned long long flags; /* * efi_fake_mem=nn@ss:attr the attr specifies * flags that might imply a soft-reservation. */ *start = memparse(p + 1, &p); if (p && *p == ':') { p++; if (kstrtoull(p, 0, &flags) < 0) *size = 0; else if (flags & EFI_MEMORY_SP) return 0; } *size = 0; } fallthrough; 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; } static void mem_avoid_memmap(enum parse_mode mode, char *str) { static int i; if (i >= MAX_MEMMAP_REGIONS) return; while (str && (i < MAX_MEMMAP_REGIONS)) { int rc; unsigned long long start, size; char *k = strchr(str, ','); if (k) *k++ = 0; rc = parse_memmap(str, &start, &size, mode); if (rc < 0) break; str = k; 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; i++; } /* More than 4 memmaps, fail kaslr */ if ((i >= MAX_MEMMAP_REGIONS) && str) memmap_too_large = true; } /* Store the number of 1GB huge pages which users specified: */ static unsigned long max_gb_huge_pages; static void parse_gb_huge_pages(char *param, char *val) { static bool gbpage_sz; char *p; if (!strcmp(param, "hugepagesz")) { p = val; if (memparse(p, &p) != PUD_SIZE) { gbpage_sz = false; return; } if (gbpage_sz) warn("Repeatedly set hugeTLB page size of 1G!\n"); gbpage_sz = true; return; } if (!strcmp(param, "hugepages") && gbpage_sz) { p = val; max_gb_huge_pages = simple_strtoull(p, &p, 0); return; } } static void handle_mem_options(void) { char *args = (char *)get_cmd_line_ptr(); size_t len = strlen((char *)args); char *tmp_cmdline; char *param, *val; u64 mem_size; if (!strstr(args, "memmap=") && !strstr(args, "mem=") && !strstr(args, "hugepages")) return; tmp_cmdline = malloc(len + 1); if (!tmp_cmdline) error("Failed to allocate space for tmp_cmdline"); memcpy(tmp_cmdline, args, len); tmp_cmdline[len] = 0; args = tmp_cmdline; /* Chew leading spaces */ args = skip_spaces(args); while (*args) { args = next_arg(args, ¶m, &val); /* Stop at -- */ if (!val && strcmp(param, "--") == 0) { warn("Only '--' specified in cmdline"); goto out; } if (!strcmp(param, "memmap")) { mem_avoid_memmap(PARSE_MEMMAP, val); } else if (strstr(param, "hugepages")) { parse_gb_huge_pages(param, val); } else if (!strcmp(param, "mem")) { char *p = val; if (!strcmp(p, "nopentium")) continue; mem_size = memparse(p, &p); if (mem_size == 0) goto out; mem_limit = mem_size; } else if (!strcmp(param, "efi_fake_mem")) { mem_avoid_memmap(PARSE_EFI, val); } } out: free(tmp_cmdline); return; } /* * In theory, KASLR can put the kernel anywhere in the range of [16M, 64T). * The mem_avoid array is used to store the ranges that need to be avoided * when KASLR searches for an appropriate random address. We must avoid any * regions that are unsafe to overlap with during decompression, and other * things like the initrd, cmdline and boot_params. This comment seeks to * explain mem_avoid as clearly as possible since incorrect mem_avoid * memory ranges lead to really hard to debug boot failures. * * The initrd, cmdline, and boot_params are trivial to identify for * avoiding. They are MEM_AVOID_INITRD, MEM_AVOID_CMDLINE, and * MEM_AVOID_BOOTPARAMS respectively below. * * What is not obvious how to avoid is the range of memory that is used * during decompression (MEM_AVOID_ZO_RANGE below). This range must cover * the compressed kernel (ZO) and its run space, which is used to extract * the uncompressed kernel (VO) and relocs. * * ZO's full run size sits against the end of the decompression buffer, so * we can calculate where text, data, bss, etc of ZO are positioned more * easily. * * For additional background, the decompression calculations can be found * in header.S, and the memory diagram is based on the one found in misc.c. * * The following conditions are already enforced by the image layouts and * associated code: * - input + input_size >= output + output_size * - kernel_total_size <= init_size * - kernel_total_size <= output_size (see Note below) * - output + init_size >= output + output_size * * (Note that kernel_total_size and output_size have no fundamental * relationship, but output_size is passed to choose_random_location * as a maximum of the two. The diagram is showing a case where * kernel_total_size is larger than output_size, but this case is * handled by bumping output_size.) * * The above conditions can be illustrated by a diagram: * * 0 output input input+input_size output+init_size * | | | | | * | | | | | * |-----|--------|--------|--------------|-----------|--|-------------| * | | | * | | | * output+init_size-ZO_INIT_SIZE output+output_size output+kernel_total_size * * [output, output+init_size) is the entire memory range used for * extracting the compressed image. * * [output, output+kernel_total_size) is the range needed for the * uncompressed kernel (VO) and its run size (bss, brk, etc). * * [output, output+output_size) is VO plus relocs (i.e. the entire * uncompressed payload contained by ZO). This is the area of the buffer * written to during decompression. * * [output+init_size-ZO_INIT_SIZE, output+init_size) is the worst-case * range of the copied ZO and decompression code. (i.e. the range * covered backwards of size ZO_INIT_SIZE, starting from output+init_size.) * * [input, input+input_size) is the original copied compressed image (ZO) * (i.e. it does not include its run size). This range must be avoided * because it contains the data used for decompression. * * [input+input_size, output+init_size) is [_text, _end) for ZO. This * range includes ZO's heap and stack, and must be avoided since it * performs the decompression. * * Since the above two ranges need to be avoided and they are adjacent, * they can be merged, resulting in: [input, output+init_size) which * becomes the MEM_AVOID_ZO_RANGE below. */ static void mem_avoid_init(unsigned long input, unsigned long input_size, unsigned long output) { unsigned long init_size = boot_params->hdr.init_size; u64 initrd_start, initrd_size; u64 cmd_line, cmd_line_size; char *ptr; /* * Avoid the region that is unsafe to overlap during * decompression. */ mem_avoid[MEM_AVOID_ZO_RANGE].start = input; mem_avoid[MEM_AVOID_ZO_RANGE].size = (output + init_size) - input; add_identity_map(mem_avoid[MEM_AVOID_ZO_RANGE].start, mem_avoid[MEM_AVOID_ZO_RANGE].size); /* Avoid initrd. */ initrd_start = (u64)boot_params->ext_ramdisk_image << 32; initrd_start |= boot_params->hdr.ramdisk_image; initrd_size = (u64)boot_params->ext_ramdisk_size << 32; initrd_size |= boot_params->hdr.ramdisk_size; mem_avoid[MEM_AVOID_INITRD].start = initrd_start; mem_avoid[MEM_AVOID_INITRD].size = initrd_size; /* No need to set mapping for initrd, it will be handled in VO. */ /* Avoid kernel command line. */ cmd_line = (u64)boot_params->ext_cmd_line_ptr << 32; cmd_line |= boot_params->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[MEM_AVOID_CMDLINE].start = cmd_line; mem_avoid[MEM_AVOID_CMDLINE].size = cmd_line_size; add_identity_map(mem_avoid[MEM_AVOID_CMDLINE].start, mem_avoid[MEM_AVOID_CMDLINE].size); /* Avoid boot parameters. */ mem_avoid[MEM_AVOID_BOOTPARAMS].start = (unsigned long)boot_params; mem_avoid[MEM_AVOID_BOOTPARAMS].size = sizeof(*boot_params); add_identity_map(mem_avoid[MEM_AVOID_BOOTPARAMS].start, mem_avoid[MEM_AVOID_BOOTPARAMS].size); /* We don't need to set a mapping for setup_data. */ /* Mark the memmap regions we need to avoid */ handle_mem_options(); /* Enumerate the immovable memory regions */ num_immovable_mem = count_immovable_mem_regions(); #ifdef CONFIG_X86_VERBOSE_BOOTUP /* Make sure video RAM can be used. */ add_identity_map(0, PMD_SIZE); #endif } /* * Does this memory vector overlap a known avoided area? If so, record the * overlap region with the lowest address. */ static bool mem_avoid_overlap(struct mem_vector *img, struct mem_vector *overlap) { int i; struct setup_data *ptr; unsigned long earliest = img->start + img->size; bool is_overlapping = false; for (i = 0; i < MEM_AVOID_MAX; i++) { if (mem_overlaps(img, &mem_avoid[i]) && mem_avoid[i].start < earliest) { *overlap = mem_avoid[i]; earliest = overlap->start; is_overlapping = true; } } /* Avoid all entries in the setup_data linked list. */ ptr = (struct setup_data *)(unsigned long)boot_params->hdr.setup_data; while (ptr) { struct mem_vector avoid; avoid.start = (unsigned long)ptr; avoid.size = sizeof(*ptr) + ptr->len; if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) { *overlap = avoid; earliest = overlap->start; is_overlapping = true; } if (ptr->type == SETUP_INDIRECT && ((struct setup_indirect *)ptr->data)->type != SETUP_INDIRECT) { avoid.start = ((struct setup_indirect *)ptr->data)->addr; avoid.size = ((struct setup_indirect *)ptr->data)->len; if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) { *overlap = avoid; earliest = overlap->start; is_overlapping = true; } } ptr = (struct setup_data *)(unsigned long)ptr->next; } return is_overlapping; } struct slot_area { unsigned long addr; int num; }; #define MAX_SLOT_AREA 100 static struct slot_area slot_areas[MAX_SLOT_AREA]; static unsigned long slot_max; static unsigned long slot_area_index; static void store_slot_info(struct mem_vector *region, unsigned long image_size) { struct slot_area slot_area; if (slot_area_index == MAX_SLOT_AREA) return; slot_area.addr = region->start; slot_area.num = (region->size - image_size) / CONFIG_PHYSICAL_ALIGN + 1; if (slot_area.num > 0) { slot_areas[slot_area_index++] = slot_area; slot_max += slot_area.num; } } /* * Skip as many 1GB huge pages as possible in the passed region * according to the number which users specified: */ static void process_gb_huge_pages(struct mem_vector *region, unsigned long image_size) { unsigned long addr, size = 0; struct mem_vector tmp; int i = 0; if (!max_gb_huge_pages) { store_slot_info(region, image_size); return; } addr = ALIGN(region->start, PUD_SIZE); /* Did we raise the address above the passed in memory entry? */ if (addr < region->start + region->size) size = region->size - (addr - region->start); /* Check how many 1GB huge pages can be filtered out: */ while (size > PUD_SIZE && max_gb_huge_pages) { size -= PUD_SIZE; max_gb_huge_pages--; i++; } /* No good 1GB huge pages found: */ if (!i) { store_slot_info(region, image_size); return; } /* * Skip those 'i'*1GB good huge pages, and continue checking and * processing the remaining head or tail part of the passed region * if available. */ if (addr >= region->start + image_size) { tmp.start = region->start; tmp.size = addr - region->start; store_slot_info(&tmp, image_size); } size = region->size - (addr - region->start) - i * PUD_SIZE; if (size >= image_size) { tmp.start = addr + i * PUD_SIZE; tmp.size = size; store_slot_info(&tmp, image_size); } } static unsigned long slots_fetch_random(void) { unsigned long slot; int i; /* Handle case of no slots stored. */ if (slot_max == 0) return 0; 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_mem_region(struct mem_vector *entry, unsigned long minimum, unsigned long image_size) { struct mem_vector region, overlap; unsigned long start_orig, end; struct mem_vector cur_entry; /* On 32-bit, ignore entries entirely above our maximum. */ if (IS_ENABLED(CONFIG_X86_32) && entry->start >= KERNEL_IMAGE_SIZE) return; /* Ignore entries entirely below our minimum. */ if (entry->start + entry->size < minimum) return; /* Ignore entries above memory limit */ end = min(entry->size + entry->start, mem_limit); if (entry->start >= end) return; cur_entry.start = entry->start; cur_entry.size = end - entry->start; region.start = cur_entry.start; region.size = cur_entry.size; /* Give up if slot area array is full. */ while (slot_area_index < MAX_SLOT_AREA) { start_orig = region.start; /* Potentially raise address to minimum location. */ if (region.start < minimum) region.start = minimum; /* 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 > cur_entry.start + cur_entry.size) return; /* Reduce size by any delta from the original address. */ region.size -= region.start - start_orig; /* 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)) { 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) { struct mem_vector beginning; beginning.start = region.start; beginning.size = overlap.start - region.start; process_gb_huge_pages(&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; } } static bool process_mem_region(struct mem_vector *region, unsigned long long minimum, unsigned long 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++) { unsigned long long 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 mirror region found (and must have been processed * for slots adding) */ 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) { /* 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; } /* Make sure minimum is aligned. */ minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN); if (process_efi_entries(minimum, image_size)) return slots_fetch_random(); process_e820_entries(minimum, image_size); return slots_fetch_random(); } static unsigned long find_random_virt_addr(unsigned long minimum, unsigned long image_size) { unsigned long slots, random_addr; /* Make sure minimum is aligned. */ minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN); /* Align image_size for easy slot calculations. */ image_size = ALIGN(image_size, CONFIG_PHYSICAL_ALIGN); /* * There are how many CONFIG_PHYSICAL_ALIGN-sized slots * that can hold image_size within the range of minimum to * KERNEL_IMAGE_SIZE? */ slots = (KERNEL_IMAGE_SIZE - minimum - image_size) / CONFIG_PHYSICAL_ALIGN + 1; 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; } #ifdef CONFIG_X86_5LEVEL if (__read_cr4() & X86_CR4_LA57) { __pgtable_l5_enabled = 1; pgdir_shift = 48; ptrs_per_p4d = 512; } #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); /* * 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 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) { add_identity_map(random_addr, output_size); *output = random_addr; } /* * This loads the identity mapping page table. * This should only be done if a new physical address * is found for the kernel, otherwise we should keep * the old page table to make it be like the "nokaslr" * case. */ finalize_identity_maps(); } /* 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; }
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