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To allow existing C code to be incorporated into the decompressor or the UEFI stub, introduce a CPP macro that turns all EXPORT_SYMBOL_xxx declarations into nops, and #define it in places where such exports are undesirable. Note that this gets rid of a rather dodgy redefine of linux/export.h's header guard. Link: http://lkml.kernel.org/r/20180704083651.24360-3-ard.biesheuvel@linaro.org Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Acked-by: Nicolas Pitre <nico@linaro.org> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Reviewed-by: Will Deacon <will.deacon@arm.com> Acked-by: Ingo Molnar <mingo@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: James Morris <james.morris@microsoft.com> Cc: James Morris <jmorris@namei.org> Cc: Jessica Yu <jeyu@kernel.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Petr Mladek <pmladek@suse.com> Cc: Russell King <linux@armlinux.org.uk> Cc: "Serge E. Hallyn" <serge@hallyn.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Garnier <thgarnie@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
868 lines
23 KiB
C
868 lines
23 KiB
C
// 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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* 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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* _ctype[] in lib/ctype.c is needed by isspace() of linux/ctype.h.
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* While both lib/ctype.c and lib/cmdline.c will bring EXPORT_SYMBOL
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* which is meaningless and will cause compiling error in some cases.
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*/
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#define __DISABLE_EXPORTS
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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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#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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/* 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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#ifdef CONFIG_X86_5LEVEL
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unsigned int __pgtable_l5_enabled;
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unsigned int pgdir_shift __ro_after_init = 39;
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unsigned int ptrs_per_p4d __ro_after_init = 1;
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#endif
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extern unsigned long get_cmd_line_ptr(void);
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/* Used by PAGE_KERN* macros: */
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pteval_t __default_kernel_pte_mask __read_mostly = ~0;
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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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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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/* 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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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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#define KASLR_COMPRESSED_BOOT
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#include "../../lib/kaslr.c"
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struct mem_vector {
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unsigned long long start;
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unsigned long long size;
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};
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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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static bool memmap_too_large;
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/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
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static unsigned long long mem_limit = ULLONG_MAX;
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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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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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static int
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parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
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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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/* 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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/* memmap=nn@ss specifies usable region, should be skipped */
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*size = 0;
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/* Fall through */
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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(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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unsigned long long 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);
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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)
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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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/* 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 int 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 = strlen((char *)args);
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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 (!strstr(args, "memmap=") && !strstr(args, "mem=") &&
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!strstr(args, "hugepages"))
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return 0;
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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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warn("Only '--' specified in cmdline");
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free(tmp_cmdline);
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return -1;
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}
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if (!strcmp(param, "memmap")) {
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mem_avoid_memmap(val);
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} else if (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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free(tmp_cmdline);
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return -EINVAL;
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}
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mem_limit = mem_size;
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}
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}
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free(tmp_cmdline);
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return 0;
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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, 64T).
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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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u64 cmd_line, cmd_line_size;
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char *ptr;
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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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add_identity_map(mem_avoid[MEM_AVOID_ZO_RANGE].start,
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mem_avoid[MEM_AVOID_ZO_RANGE].size);
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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 = (u64)boot_params->ext_cmd_line_ptr << 32;
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cmd_line |= boot_params->hdr.cmd_line_ptr;
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/* Calculate size of cmd_line. */
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ptr = (char *)(unsigned long)cmd_line;
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for (cmd_line_size = 0; ptr[cmd_line_size++];)
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;
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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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add_identity_map(mem_avoid[MEM_AVOID_CMDLINE].start,
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mem_avoid[MEM_AVOID_CMDLINE].size);
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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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add_identity_map(mem_avoid[MEM_AVOID_BOOTPARAMS].start,
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mem_avoid[MEM_AVOID_BOOTPARAMS].size);
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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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#ifdef CONFIG_X86_VERBOSE_BOOTUP
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/* Make sure video RAM can be used. */
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add_identity_map(0, PMD_SIZE);
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#endif
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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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unsigned long 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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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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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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unsigned long addr;
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int 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 long slot_max;
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|
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;
|
|
struct slot_area slot_area;
|
|
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;
|
|
}
|
|
}
|
|
|
|
#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_mirror_found &&
|
|
!(md->attribute & EFI_MEMORY_MORE_RELIABLE))
|
|
continue;
|
|
|
|
region.start = md->phys_addr;
|
|
region.size = md->num_pages << EFI_PAGE_SHIFT;
|
|
process_mem_region(®ion, minimum, image_size);
|
|
if (slot_area_index == MAX_SLOT_AREA) {
|
|
debug_putstr("Aborted EFI scan (slot_areas full)!\n");
|
|
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;
|
|
process_mem_region(®ion, minimum, image_size);
|
|
if (slot_area_index == MAX_SLOT_AREA) {
|
|
debug_putstr("Aborted e820 scan (slot_areas full)!\n");
|
|
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;
|
|
}
|