diff options
Diffstat (limited to 'arch/arm64/kernel/kaslr.c')
| -rw-r--r-- | arch/arm64/kernel/kaslr.c | 67 |
1 files changed, 56 insertions, 11 deletions
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c index 708051655ad9..91a83104c6e8 100644 --- a/arch/arm64/kernel/kaslr.c +++ b/arch/arm64/kernel/kaslr.c @@ -11,6 +11,7 @@ #include <linux/sched.h> #include <linux/types.h> +#include <asm/archrandom.h> #include <asm/cacheflush.h> #include <asm/fixmap.h> #include <asm/kernel-pgtable.h> @@ -19,6 +20,14 @@ #include <asm/pgtable.h> #include <asm/sections.h> +enum kaslr_status { + KASLR_ENABLED, + KASLR_DISABLED_CMDLINE, + KASLR_DISABLED_NO_SEED, + KASLR_DISABLED_FDT_REMAP, +}; + +static enum kaslr_status __initdata kaslr_status; u64 __ro_after_init module_alloc_base; u16 __initdata memstart_offset_seed; @@ -62,9 +71,6 @@ out: return default_cmdline; } -extern void *__init __fixmap_remap_fdt(phys_addr_t dt_phys, int *size, - pgprot_t prot); - /* * This routine will be executed with the kernel mapped at its default virtual * address, and if it returns successfully, the kernel will be remapped, and @@ -93,16 +99,16 @@ u64 __init kaslr_early_init(u64 dt_phys) * attempt at mapping the FDT in setup_machine() */ early_fixmap_init(); - fdt = __fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL); - if (!fdt) + fdt = fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL); + if (!fdt) { + kaslr_status = KASLR_DISABLED_FDT_REMAP; return 0; + } /* * Retrieve (and wipe) the seed from the FDT */ seed = get_kaslr_seed(fdt); - if (!seed) - return 0; /* * Check if 'nokaslr' appears on the command line, and @@ -110,21 +116,39 @@ u64 __init kaslr_early_init(u64 dt_phys) */ cmdline = kaslr_get_cmdline(fdt); str = strstr(cmdline, "nokaslr"); - if (str == cmdline || (str > cmdline && *(str - 1) == ' ')) + if (str == cmdline || (str > cmdline && *(str - 1) == ' ')) { + kaslr_status = KASLR_DISABLED_CMDLINE; + return 0; + } + + /* + * Mix in any entropy obtainable architecturally, open coded + * since this runs extremely early. + */ + if (__early_cpu_has_rndr()) { + unsigned long raw; + + if (__arm64_rndr(&raw)) + seed ^= raw; + } + + if (!seed) { + kaslr_status = KASLR_DISABLED_NO_SEED; return 0; + } /* * OK, so we are proceeding with KASLR enabled. Calculate a suitable * kernel image offset from the seed. Let's place the kernel in the - * middle half of the VMALLOC area (VA_BITS - 2), and stay clear of + * middle half of the VMALLOC area (VA_BITS_MIN - 2), and stay clear of * the lower and upper quarters to avoid colliding with other * allocations. * Even if we could randomize at page granularity for 16k and 64k pages, * let's always round to 2 MB so we don't interfere with the ability to * map using contiguous PTEs */ - mask = ((1UL << (VA_BITS - 2)) - 1) & ~(SZ_2M - 1); - offset = BIT(VA_BITS - 3) + (seed & mask); + mask = ((1UL << (VA_BITS_MIN - 2)) - 1) & ~(SZ_2M - 1); + offset = BIT(VA_BITS_MIN - 3) + (seed & mask); /* use the top 16 bits to randomize the linear region */ memstart_offset_seed = seed >> 48; @@ -173,3 +197,24 @@ u64 __init kaslr_early_init(u64 dt_phys) return offset; } + +static int __init kaslr_init(void) +{ + switch (kaslr_status) { + case KASLR_ENABLED: + pr_info("KASLR enabled\n"); + break; + case KASLR_DISABLED_CMDLINE: + pr_info("KASLR disabled on command line\n"); + break; + case KASLR_DISABLED_NO_SEED: + pr_warn("KASLR disabled due to lack of seed\n"); + break; + case KASLR_DISABLED_FDT_REMAP: + pr_warn("KASLR disabled due to FDT remapping failure\n"); + break; + } + + return 0; +} +core_initcall(kaslr_init) |
