linux-kernel - [PATCH 1/2] riscv: allocate a complete page size for each page table

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Date:   Fri,  7 Feb 2020 17:52:44 +0800
From:   Zong Li <zong.li@...ive.com>
To:     paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     Zong Li <zong.li@...ive.com>
Subject: [PATCH 1/2] riscv: allocate a complete page size for each page table

Each page table should be created by allocating a complete page size
for it. Otherwise, the content of the page table would be corrupted
somewhere through memory allocation which allocates the memory at the
middle of the page table for other use.

Signed-off-by: Zong Li <zong.li@...ive.com>
---
 arch/riscv/mm/kasan_init.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
index f0cc86040587..f8eaf7e73a23 100644
--- a/arch/riscv/mm/kasan_init.c
+++ b/arch/riscv/mm/kasan_init.c
@@ -46,29 +46,34 @@ asmlinkage void __init kasan_early_init(void)
 
 static void __init populate(void *start, void *end)
 {
-	unsigned long i;
+	unsigned long i, offset;
 	unsigned long vaddr = (unsigned long)start & PAGE_MASK;
 	unsigned long vend = PAGE_ALIGN((unsigned long)end);
 	unsigned long n_pages = (vend - vaddr) / PAGE_SIZE;
+	unsigned long n_ptes =
+	    ((n_pages + PTRS_PER_PTE) & -PTRS_PER_PTE) / PTRS_PER_PTE;
 	unsigned long n_pmds =
-		(n_pages % PTRS_PER_PTE) ? n_pages / PTRS_PER_PTE + 1 :
-						n_pages / PTRS_PER_PTE;
+	    ((n_ptes + PTRS_PER_PMD) & -PTRS_PER_PMD) / PTRS_PER_PMD;
+
+	pte_t *pte =
+	    memblock_alloc(n_ptes * PTRS_PER_PTE * sizeof(pte_t), PAGE_SIZE);
+	pmd_t *pmd =
+	    memblock_alloc(n_pmds * PTRS_PER_PMD * sizeof(pmd_t), PAGE_SIZE);
 	pgd_t *pgd = pgd_offset_k(vaddr);
-	pmd_t *pmd = memblock_alloc(n_pmds * sizeof(pmd_t), PAGE_SIZE);
-	pte_t *pte = memblock_alloc(n_pages * sizeof(pte_t), PAGE_SIZE);
 
 	for (i = 0; i < n_pages; i++) {
 		phys_addr_t phys = memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
-
-		set_pte(pte + i, pfn_pte(PHYS_PFN(phys), PAGE_KERNEL));
+		set_pte(&pte[i], pfn_pte(PHYS_PFN(phys), PAGE_KERNEL));
 	}
 
-	for (i = 0; i < n_pmds; ++pgd, i += PTRS_PER_PMD)
-		set_pgd(pgd, pfn_pgd(PFN_DOWN(__pa(((uintptr_t)(pmd + i)))),
+	for (i = 0, offset = 0; i < n_ptes; i++, offset += PTRS_PER_PTE)
+		set_pmd(&pmd[i],
+			pfn_pmd(PFN_DOWN(__pa(&pte[offset])),
 				__pgprot(_PAGE_TABLE)));
 
-	for (i = 0; i < n_pages; ++pmd, i += PTRS_PER_PTE)
-		set_pmd(pmd, pfn_pmd(PFN_DOWN(__pa((uintptr_t)(pte + i))),
+	for (i = 0, offset = 0; i < n_pmds; i++, offset += PTRS_PER_PMD)
+		set_pgd(&pgd[i],
+			pfn_pgd(PFN_DOWN(__pa(&pmd[offset])),
 				__pgprot(_PAGE_TABLE)));
 
 	flush_tlb_all();
-- 
2.25.0