diff options
Diffstat (limited to 'arch/arm64/kernel/kaslr.c')
-rw-r--r-- | arch/arm64/kernel/kaslr.c | 83 |
1 files changed, 14 insertions, 69 deletions
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c index e7477f21a4c9..17f96a19781d 100644 --- a/arch/arm64/kernel/kaslr.c +++ b/arch/arm64/kernel/kaslr.c @@ -4,90 +4,35 @@ */ #include <linux/cache.h> -#include <linux/crc32.h> #include <linux/init.h> -#include <linux/libfdt.h> -#include <linux/mm_types.h> -#include <linux/sched.h> -#include <linux/types.h> -#include <linux/pgtable.h> -#include <linux/random.h> +#include <linux/printk.h> -#include <asm/fixmap.h> -#include <asm/kernel-pgtable.h> +#include <asm/cpufeature.h> #include <asm/memory.h> -#include <asm/mmu.h> -#include <asm/sections.h> -#include <asm/setup.h> -u64 __ro_after_init module_alloc_base; u16 __initdata memstart_offset_seed; struct arm64_ftr_override kaslr_feature_override __initdata; -static int __init kaslr_init(void) -{ - u64 module_range; - u32 seed; - - /* - * Set a reasonable default for module_alloc_base in case - * we end up running with module randomization disabled. - */ - module_alloc_base = (u64)_etext - MODULES_VSIZE; +bool __ro_after_init __kaslr_is_enabled = false; +void __init kaslr_init(void) +{ if (kaslr_feature_override.val & kaslr_feature_override.mask & 0xf) { pr_info("KASLR disabled on command line\n"); - return 0; - } - - if (!kaslr_enabled()) { - pr_warn("KASLR disabled due to lack of seed\n"); - return 0; + return; } - pr_info("KASLR enabled\n"); - /* - * KASAN without KASAN_VMALLOC does not expect the module region to - * intersect the vmalloc region, since shadow memory is allocated for - * each module at load time, whereas the vmalloc region will already be - * shadowed by KASAN zero pages. + * The KASLR offset modulo MIN_KIMG_ALIGN is taken from the physical + * placement of the image rather than from the seed, so a displacement + * of less than MIN_KIMG_ALIGN means that no seed was provided. */ - BUILD_BUG_ON((IS_ENABLED(CONFIG_KASAN_GENERIC) || - IS_ENABLED(CONFIG_KASAN_SW_TAGS)) && - !IS_ENABLED(CONFIG_KASAN_VMALLOC)); - - seed = get_random_u32(); - - if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) { - /* - * Randomize the module region over a 2 GB window covering the - * kernel. This reduces the risk of modules leaking information - * about the address of the kernel itself, but results in - * branches between modules and the core kernel that are - * resolved via PLTs. (Branches between modules will be - * resolved normally.) - */ - module_range = SZ_2G - (u64)(_end - _stext); - module_alloc_base = max((u64)_end - SZ_2G, (u64)MODULES_VADDR); - } else { - /* - * Randomize the module region by setting module_alloc_base to - * a PAGE_SIZE multiple in the range [_etext - MODULES_VSIZE, - * _stext) . This guarantees that the resulting region still - * covers [_stext, _etext], and that all relative branches can - * be resolved without veneers unless this region is exhausted - * and we fall back to a larger 2GB window in module_alloc() - * when ARM64_MODULE_PLTS is enabled. - */ - module_range = MODULES_VSIZE - (u64)(_etext - _stext); + if (kaslr_offset() < MIN_KIMG_ALIGN) { + pr_warn("KASLR disabled due to lack of seed\n"); + return; } - /* use the lower 21 bits to randomize the base of the module region */ - module_alloc_base += (module_range * (seed & ((1 << 21) - 1))) >> 21; - module_alloc_base &= PAGE_MASK; - - return 0; + pr_info("KASLR enabled\n"); + __kaslr_is_enabled = true; } -subsys_initcall(kaslr_init) |