/* Initialize base and padding for each memory region randomized with KASLR */ void __init kernel_randomize_memory(void) { size_t i; unsigned long vaddr_start, vaddr; unsigned long rand, memory_tb; struct rnd_state rand_state; unsigned long remain_entropy; vaddr_start = pgtable_l5_enabled() ? __PAGE_OFFSET_BASE_L5 : __PAGE_OFFSET_BASE_L4; vaddr = vaddr_start; /* * These BUILD_BUG_ON checks ensure the memory layout is consistent * with the vaddr_start/vaddr_end variables. These checks are very * limited.... */ BUILD_BUG_ON(vaddr_start >= vaddr_end); BUILD_BUG_ON(vaddr_end != CPU_ENTRY_AREA_BASE); BUILD_BUG_ON(vaddr_end > __START_KERNEL_map); if (!kaslr_memory_enabled()) return; kaslr_regions[0].size_tb = 1 << (MAX_PHYSMEM_BITS - TB_SHIFT); kaslr_regions[1].size_tb = VMALLOC_SIZE_TB; /* * Update Physical memory mapping to available and * add padding if needed (especially for memory hotplug support). */ BUG_ON(kaslr_regions[0].base != &page_offset_base); memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) + CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING; /* Adapt phyiscal memory region size based on available memory */ if (memory_tb < kaslr_regions[0].size_tb) kaslr_regions[0].size_tb = memory_tb; /* Calculate entropy available between regions */ remain_entropy = vaddr_end - vaddr_start; for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++) remain_entropy -= get_padding(&kaslr_regions[i]); prandom_seed_state(&rand_state, kaslr_get_random_long("Memory")); for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++) { unsigned long entropy; /* * Select a random virtual address using the extra entropy * available. */ entropy = remain_entropy / (ARRAY_SIZE(kaslr_regions) - i); prandom_bytes_state(&rand_state, &rand, sizeof(rand)); entropy = (rand % (entropy + 1)) & PUD_MASK; vaddr += entropy; *kaslr_regions[i].base = vaddr; /* * Jump the region and add a minimum padding based on * randomization alignment. */ vaddr += get_padding(&kaslr_regions[i]); vaddr = round_up(vaddr + 1, PUD_SIZE); remain_entropy -= entropy; } }
/* Initialize base and padding for each memory region randomized with KASLR */ void __init kernel_randomize_memory(void) { size_t i; unsigned long vaddr = vaddr_start; unsigned long rand, memory_tb; struct rnd_state rand_state; unsigned long remain_entropy; /* * All these BUILD_BUG_ON checks ensures the memory layout is * consistent with the vaddr_start/vaddr_end variables. */ BUILD_BUG_ON(vaddr_start >= vaddr_end); BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_ESPFIX64) && vaddr_end >= EFI_VA_END); BUILD_BUG_ON((IS_ENABLED(CONFIG_X86_ESPFIX64) || IS_ENABLED(CONFIG_EFI)) && vaddr_end >= __START_KERNEL_map); BUILD_BUG_ON(vaddr_end > __START_KERNEL_map); if (!kaslr_memory_enabled()) return; /* * Update Physical memory mapping to available and * add padding if needed (especially for memory hotplug support). */ BUG_ON(kaslr_regions[0].base != &page_offset_base); memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) + CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING; /* Adapt phyiscal memory region size based on available memory */ if (memory_tb < kaslr_regions[0].size_tb) kaslr_regions[0].size_tb = memory_tb; /* Calculate entropy available between regions */ remain_entropy = vaddr_end - vaddr_start; for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++) remain_entropy -= get_padding(&kaslr_regions[i]); prandom_seed_state(&rand_state, kaslr_get_random_long("Memory")); for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++) { unsigned long entropy; /* * Select a random virtual address using the extra entropy * available. */ entropy = remain_entropy / (ARRAY_SIZE(kaslr_regions) - i); prandom_bytes_state(&rand_state, &rand, sizeof(rand)); entropy = (rand % (entropy + 1)) & PUD_MASK; vaddr += entropy; *kaslr_regions[i].base = vaddr; /* * Jump the region and add a minimum padding based on * randomization alignment. */ vaddr += get_padding(&kaslr_regions[i]); vaddr = round_up(vaddr + 1, PUD_SIZE); remain_entropy -= entropy; } }