On 04/15/19 at 09:47pm, Borislav Petkov wrote: > On Sun, Apr 14, 2019 at 03:28:04PM +0800, Baoquan He wrote: > > kernel_randomize_memory() hardcodes the size of vmemmap section as 1 TB, > > to support the maximum amount of system RAM in 4-level paging mode, 64 TB. > > > > However, 1 TB is not enough for vmemmap in 5-level paging mode. Assuming > > the size of struct page is 64 Bytes, to support 4 PB system RAM in 5-level, > > 64 TB of vmemmap area is needed. The wrong hardcoding may cause vmemmap > > stamping into the following cpu_entry_area section, if KASLR puts vmemmap > > very close to cpu_entry_area, and the actual area of vmemmap is much bigger > > than 1 TB. > > > > So here calculate the actual size of vmemmap region, then align up to 1 TB > > boundary. In 4-level it's always 1 TB. In 5-level it's adjusted on demand. > > The current code reserves 0.5 PB for vmemmap in 5-level. In this new methor, > ^^^^^^^ > > Please introduce a spellchecker into your patch creation workflow.
Sorry, forgot running checkpatch this time. Will update. > > > the left space can be saved to join randomization to increase the entropy. > > > > Signed-off-by: Baoquan He <b...@redhat.com> > > --- > > arch/x86/mm/kaslr.c | 11 ++++++++++- > > 1 file changed, 10 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c > > index 387d4ed25d7c..4679a0075048 100644 > > --- a/arch/x86/mm/kaslr.c > > +++ b/arch/x86/mm/kaslr.c > > @@ -52,7 +52,7 @@ static __initdata struct kaslr_memory_region { > > } kaslr_regions[] = { > > { &page_offset_base, 0 }, > > { &vmalloc_base, 0 }, > > - { &vmemmap_base, 1 }, > > + { &vmemmap_base, 0 }, > > }; > > > > /* Get size in bytes used by the memory region */ > > @@ -78,6 +78,7 @@ void __init kernel_randomize_memory(void) > > unsigned long rand, memory_tb; > > struct rnd_state rand_state; > > unsigned long remain_entropy; > > + unsigned long vmemmap_size; > > > > vaddr_start = pgtable_l5_enabled() ? __PAGE_OFFSET_BASE_L5 : > > __PAGE_OFFSET_BASE_L4; > > vaddr = vaddr_start; > > @@ -109,6 +110,14 @@ void __init kernel_randomize_memory(void) > > if (memory_tb < kaslr_regions[0].size_tb) > > kaslr_regions[0].size_tb = memory_tb; > > > > + /** > > + * Calculate how many TB vmemmap region needs, and aligned to > > + * 1TB boundary. > > + */ > > + vmemmap_size = (kaslr_regions[0].size_tb << (TB_SHIFT - PAGE_SHIFT)) * > > + sizeof(struct page); > > + kaslr_regions[2].size_tb = DIV_ROUND_UP(vmemmap_size, 1UL << TB_SHIFT); > > + > > /* Calculate entropy available between regions */ > > remain_entropy = vaddr_end - vaddr_start; > > for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++) > > -- > > Kirill, ack? > > -- > Regards/Gruss, > Boris. > > Good mailing practices for 400: avoid top-posting and trim the reply.