From: Masayoshi Mizuma <[email protected]> Cleanup calculation for direct mapping size.
Signed-off-by: Baoquan He <[email protected]> Signed-off-by: Masayoshi Mizuma <[email protected]> --- arch/x86/mm/kaslr.c | 50 +++++++++++++++++++++++++++++++-------------- 1 file changed, 35 insertions(+), 15 deletions(-) diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index dc6182eec..8e5f3642e 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -70,15 +70,45 @@ static inline bool kaslr_memory_enabled(void) return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN); } +/* + * Even though a huge virtual address space is reserved for the direct + * mapping of physical memory, e.g in 4-level paging mode, it's 64TB, + * rare system can own enough physical memory to use it up, most are + * even less than 1TB. So with KASLR enabled, we adapt the size of + * direct mapping area to the size of actual physical memory plus the + * configured padding CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING. + * The left part will be taken out to join memory randomization. + */ +static inline unsigned long calc_direct_mapping_size(void) +{ + unsigned long size_tb, memory_tb; + + /* + * Update Physical memory mapping to available and + * add padding if needed (especially for memory hotplug support). + */ + memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) + + CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING; + + size_tb = 1 << (MAX_PHYSMEM_BITS - TB_SHIFT); + + /* + * Adapt physical memory region size based on available memory + */ + if (memory_tb < size_tb) + size_tb = memory_tb; + + return size_tb; +} + /* 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 vaddr_start, vaddr, rand; unsigned long remain_entropy; unsigned long vmemmap_size; + struct rnd_state rand_state; + size_t i; vaddr_start = pgtable_l5_enabled() ? __PAGE_OFFSET_BASE_L5 : __PAGE_OFFSET_BASE_L4; vaddr = vaddr_start; @@ -95,20 +125,10 @@ void __init kernel_randomize_memory(void) if (!kaslr_memory_enabled()) return; - kaslr_regions[0].size_tb = 1 << (MAX_PHYSMEM_BITS - TB_SHIFT); + kaslr_regions[0].size_tb = calc_direct_mapping_size(); 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 the vmemmap region size in TBs, aligned to a TB -- 2.18.1
