Messages in this thread Patch in this message | | | From | Baoquan He <> | Subject | [PATCH 2/2] x86/mm/KASLR: Calculate the actual size of vmemmap region | Date | Thu, 4 Apr 2019 10:03:14 +0800 |
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Vmemmap region has different maximum size depending on paging mode. However, its size is hardcoded as 1TB during memory KASLR handling, this is not right for 5-level paging mode since it will cause vital stumping if vmemmap region is randomized to be very close to the following cpu_entry_area region and the actual size of vmemmap is much bigger than 1 TB.
So here calculate how many TB needed by the actual size of vmemmap region and align up to 1TB boundary. In 4-level the size will be 1 TB always since the max is 1 TB. In 5-level it's variable so that space can be saved for randomization.
Signed-off-by: Baoquan He <bhe@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++) -- 2.17.2
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