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https://github.com/torvalds/linux
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c633544a61
Cover kernel addresses above 0x90000000 by the shadow map. Enable HAVE_ARCH_KASAN when MMU is enabled. Provide kasan_early_init that fills shadow map with writable copies of kasan_zero_page. Call kasan_early_init right after mmu initialization in the setup_arch. Provide kasan_init that allocates proper shadow map pages from the memblock and puts these pages into the shadow map for addresses from VMALLOC area to the end of KSEG. Call kasan_init right after memblock initialization. Don't use KASAN for the boot code, MMU and KASAN initialization and page fault handler. Make kernel stack size 4 times larger when KASAN is enabled to avoid stack overflows. GCC 7.3, 8 or newer is required to build the xtensa kernel with KASAN. Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
96 lines
2.6 KiB
C
96 lines
2.6 KiB
C
/*
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* Xtensa KASAN shadow map initialization
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Copyright (C) 2017 Cadence Design Systems Inc.
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*/
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#include <linux/bootmem.h>
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#include <linux/init_task.h>
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#include <linux/kasan.h>
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#include <linux/kernel.h>
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#include <linux/memblock.h>
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#include <asm/initialize_mmu.h>
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#include <asm/tlbflush.h>
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#include <asm/traps.h>
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void __init kasan_early_init(void)
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{
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unsigned long vaddr = KASAN_SHADOW_START;
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pgd_t *pgd = pgd_offset_k(vaddr);
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pmd_t *pmd = pmd_offset(pgd, vaddr);
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int i;
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for (i = 0; i < PTRS_PER_PTE; ++i)
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set_pte(kasan_zero_pte + i,
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mk_pte(virt_to_page(kasan_zero_page), PAGE_KERNEL));
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for (vaddr = 0; vaddr < KASAN_SHADOW_SIZE; vaddr += PMD_SIZE, ++pmd) {
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BUG_ON(!pmd_none(*pmd));
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set_pmd(pmd, __pmd((unsigned long)kasan_zero_pte));
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}
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early_trap_init();
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}
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static void __init populate(void *start, void *end)
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{
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unsigned long n_pages = (end - start) / PAGE_SIZE;
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unsigned long n_pmds = n_pages / PTRS_PER_PTE;
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unsigned long i, j;
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unsigned long vaddr = (unsigned long)start;
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pgd_t *pgd = pgd_offset_k(vaddr);
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pmd_t *pmd = pmd_offset(pgd, vaddr);
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pte_t *pte = memblock_virt_alloc(n_pages * sizeof(pte_t), PAGE_SIZE);
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pr_debug("%s: %p - %p\n", __func__, start, end);
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for (i = j = 0; i < n_pmds; ++i) {
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int k;
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for (k = 0; k < PTRS_PER_PTE; ++k, ++j) {
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phys_addr_t phys =
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memblock_alloc_base(PAGE_SIZE, PAGE_SIZE,
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MEMBLOCK_ALLOC_ANYWHERE);
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set_pte(pte + j, pfn_pte(PHYS_PFN(phys), PAGE_KERNEL));
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}
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}
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for (i = 0; i < n_pmds ; ++i, pte += PTRS_PER_PTE)
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set_pmd(pmd + i, __pmd((unsigned long)pte));
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local_flush_tlb_all();
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memset(start, 0, end - start);
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}
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void __init kasan_init(void)
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{
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int i;
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BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_START -
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(KASAN_START_VADDR >> KASAN_SHADOW_SCALE_SHIFT));
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BUILD_BUG_ON(VMALLOC_START < KASAN_START_VADDR);
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/*
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* Replace shadow map pages that cover addresses from VMALLOC area
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* start to the end of KSEG with clean writable pages.
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*/
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populate(kasan_mem_to_shadow((void *)VMALLOC_START),
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kasan_mem_to_shadow((void *)XCHAL_KSEG_BYPASS_VADDR));
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/* Write protect kasan_zero_page and zero-initialize it again. */
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for (i = 0; i < PTRS_PER_PTE; ++i)
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set_pte(kasan_zero_pte + i,
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mk_pte(virt_to_page(kasan_zero_page), PAGE_KERNEL_RO));
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local_flush_tlb_all();
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memset(kasan_zero_page, 0, PAGE_SIZE);
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/* At this point kasan is fully initialized. Enable error messages. */
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current->kasan_depth = 0;
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pr_info("KernelAddressSanitizer initialized\n");
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}
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