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9bceb80b3c
Commit585524081e
("random: random.h should include archrandom.h, not the other way around") tries to fix a problem with recursive inclusion of linux/random.h and arch/archrandom.h for arm64. Unfortunately, this results in the following compile error if ARCH_RANDOM is disabled. arch/arm64/kernel/kaslr.c: In function 'kaslr_early_init': arch/arm64/kernel/kaslr.c:128:6: error: implicit declaration of function '__early_cpu_has_rndr'; did you mean '__early_pfn_to_nid'? [-Werror=implicit-function-declaration] if (__early_cpu_has_rndr()) { ^~~~~~~~~~~~~~~~~~~~ __early_pfn_to_nid arch/arm64/kernel/kaslr.c:131:7: error: implicit declaration of function '__arm64_rndr' [-Werror=implicit-function-declaration] if (__arm64_rndr(&raw)) ^~~~~~~~~~~~ The problem is that arch/archrandom.h is only included from linux/random.h if ARCH_RANDOM is enabled. If not, __arm64_rndr() and __early_cpu_has_rndr() are undeclared, causing the problem. Use arch_get_random_seed_long_early() instead of arm64 specific functions to solve the problem. Reported-by: Qian Cai <cai@lca.pw> Fixes:585524081e
("random: random.h should include archrandom.h, not the other way around") Cc: Qian Cai <cai@lca.pw> Cc: Mark Brown <broonie@kernel.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Mark Brown <broonie@kernel.org> Tested-by: Mark Brown <broonie@kernel.org> Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
219 lines
5.9 KiB
C
219 lines
5.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2016 Linaro Ltd <ard.biesheuvel@linaro.org>
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*/
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#include <linux/cache.h>
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#include <linux/crc32.h>
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#include <linux/init.h>
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#include <linux/libfdt.h>
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#include <linux/mm_types.h>
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#include <linux/sched.h>
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#include <linux/types.h>
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#include <linux/pgtable.h>
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#include <linux/random.h>
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#include <asm/cacheflush.h>
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#include <asm/fixmap.h>
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#include <asm/kernel-pgtable.h>
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#include <asm/memory.h>
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#include <asm/mmu.h>
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#include <asm/sections.h>
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enum kaslr_status {
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KASLR_ENABLED,
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KASLR_DISABLED_CMDLINE,
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KASLR_DISABLED_NO_SEED,
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KASLR_DISABLED_FDT_REMAP,
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};
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static enum kaslr_status __initdata kaslr_status;
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u64 __ro_after_init module_alloc_base;
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u16 __initdata memstart_offset_seed;
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static __init u64 get_kaslr_seed(void *fdt)
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{
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int node, len;
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fdt64_t *prop;
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u64 ret;
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node = fdt_path_offset(fdt, "/chosen");
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if (node < 0)
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return 0;
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prop = fdt_getprop_w(fdt, node, "kaslr-seed", &len);
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if (!prop || len != sizeof(u64))
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return 0;
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ret = fdt64_to_cpu(*prop);
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*prop = 0;
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return ret;
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}
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static __init const u8 *kaslr_get_cmdline(void *fdt)
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{
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static __initconst const u8 default_cmdline[] = CONFIG_CMDLINE;
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if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
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int node;
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const u8 *prop;
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node = fdt_path_offset(fdt, "/chosen");
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if (node < 0)
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goto out;
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prop = fdt_getprop(fdt, node, "bootargs", NULL);
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if (!prop)
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goto out;
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return prop;
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}
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out:
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return default_cmdline;
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}
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/*
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* This routine will be executed with the kernel mapped at its default virtual
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* address, and if it returns successfully, the kernel will be remapped, and
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* start_kernel() will be executed from a randomized virtual offset. The
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* relocation will result in all absolute references (e.g., static variables
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* containing function pointers) to be reinitialized, and zero-initialized
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* .bss variables will be reset to 0.
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*/
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u64 __init kaslr_early_init(u64 dt_phys)
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{
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void *fdt;
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u64 seed, offset, mask, module_range;
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const u8 *cmdline, *str;
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unsigned long raw;
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int size;
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/*
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* Set a reasonable default for module_alloc_base in case
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* we end up running with module randomization disabled.
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*/
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module_alloc_base = (u64)_etext - MODULES_VSIZE;
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__flush_dcache_area(&module_alloc_base, sizeof(module_alloc_base));
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/*
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* Try to map the FDT early. If this fails, we simply bail,
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* and proceed with KASLR disabled. We will make another
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* attempt at mapping the FDT in setup_machine()
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*/
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early_fixmap_init();
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fdt = fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL);
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if (!fdt) {
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kaslr_status = KASLR_DISABLED_FDT_REMAP;
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return 0;
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}
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/*
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* Retrieve (and wipe) the seed from the FDT
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*/
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seed = get_kaslr_seed(fdt);
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/*
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* Check if 'nokaslr' appears on the command line, and
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* return 0 if that is the case.
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*/
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cmdline = kaslr_get_cmdline(fdt);
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str = strstr(cmdline, "nokaslr");
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if (str == cmdline || (str > cmdline && *(str - 1) == ' ')) {
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kaslr_status = KASLR_DISABLED_CMDLINE;
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return 0;
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}
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/*
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* Mix in any entropy obtainable architecturally if enabled
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* and supported.
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*/
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if (arch_get_random_seed_long_early(&raw))
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seed ^= raw;
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if (!seed) {
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kaslr_status = KASLR_DISABLED_NO_SEED;
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return 0;
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}
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/*
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* OK, so we are proceeding with KASLR enabled. Calculate a suitable
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* kernel image offset from the seed. Let's place the kernel in the
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* middle half of the VMALLOC area (VA_BITS_MIN - 2), and stay clear of
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* the lower and upper quarters to avoid colliding with other
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* allocations.
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* Even if we could randomize at page granularity for 16k and 64k pages,
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* let's always round to 2 MB so we don't interfere with the ability to
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* map using contiguous PTEs
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*/
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mask = ((1UL << (VA_BITS_MIN - 2)) - 1) & ~(SZ_2M - 1);
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offset = BIT(VA_BITS_MIN - 3) + (seed & mask);
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/* use the top 16 bits to randomize the linear region */
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memstart_offset_seed = seed >> 48;
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if (IS_ENABLED(CONFIG_KASAN))
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/*
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* KASAN does not expect the module region to intersect the
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* vmalloc region, since shadow memory is allocated for each
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* module at load time, whereas the vmalloc region is shadowed
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* by KASAN zero pages. So keep modules out of the vmalloc
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* region if KASAN is enabled, and put the kernel well within
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* 4 GB of the module region.
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*/
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return offset % SZ_2G;
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if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {
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/*
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* Randomize the module region over a 2 GB window covering the
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* kernel. This reduces the risk of modules leaking information
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* about the address of the kernel itself, but results in
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* branches between modules and the core kernel that are
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* resolved via PLTs. (Branches between modules will be
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* resolved normally.)
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*/
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module_range = SZ_2G - (u64)(_end - _stext);
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module_alloc_base = max((u64)_end + offset - SZ_2G,
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(u64)MODULES_VADDR);
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} else {
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/*
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* Randomize the module region by setting module_alloc_base to
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* a PAGE_SIZE multiple in the range [_etext - MODULES_VSIZE,
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* _stext) . This guarantees that the resulting region still
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* covers [_stext, _etext], and that all relative branches can
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* be resolved without veneers.
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*/
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module_range = MODULES_VSIZE - (u64)(_etext - _stext);
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module_alloc_base = (u64)_etext + offset - MODULES_VSIZE;
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}
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/* use the lower 21 bits to randomize the base of the module region */
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module_alloc_base += (module_range * (seed & ((1 << 21) - 1))) >> 21;
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module_alloc_base &= PAGE_MASK;
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__flush_dcache_area(&module_alloc_base, sizeof(module_alloc_base));
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__flush_dcache_area(&memstart_offset_seed, sizeof(memstart_offset_seed));
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return offset;
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}
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static int __init kaslr_init(void)
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{
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switch (kaslr_status) {
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case KASLR_ENABLED:
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pr_info("KASLR enabled\n");
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break;
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case KASLR_DISABLED_CMDLINE:
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pr_info("KASLR disabled on command line\n");
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break;
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case KASLR_DISABLED_NO_SEED:
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pr_warn("KASLR disabled due to lack of seed\n");
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break;
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case KASLR_DISABLED_FDT_REMAP:
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pr_warn("KASLR disabled due to FDT remapping failure\n");
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break;
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}
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return 0;
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}
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core_initcall(kaslr_init)
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