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ea3186b957
Commit
b4e0409a36 ("x86: check vmlinux limits, 64-bit")
added a check that the size of the 64-bit kernel is less than
KERNEL_IMAGE_SIZE.
The check uses (_end - _text), but this is not enough. The initial
PMD used in startup_64() (level2_kernel_pgt) can only map upto
KERNEL_IMAGE_SIZE from __START_KERNEL_map, not from _text, and the
modules area (MODULES_VADDR) starts at KERNEL_IMAGE_SIZE.
The correct check is what is currently done for 32-bit, since
LOAD_OFFSET is defined appropriately for the two architectures. Just
check (_end - LOAD_OFFSET) against KERNEL_IMAGE_SIZE unconditionally.
Note that on 32-bit, the limit is not strict: KERNEL_IMAGE_SIZE is not
really used by the main kernel. The higher the kernel is located, the
less the space available for the vmalloc area. However, it is used by
KASLR in the compressed stub to limit the maximum address of the kernel
to a safe value.
Clean up various comments to clarify that despite the name,
KERNEL_IMAGE_SIZE is not a limit on the size of the kernel image, but a
limit on the maximum virtual address that the image can occupy.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20201029161903.2553528-1-nivedita@alum.mit.edu
84 lines
2.3 KiB
C
84 lines
2.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_PGTABLE_32_H
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#define _ASM_X86_PGTABLE_32_H
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#include <asm/pgtable_32_types.h>
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/*
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* The Linux memory management assumes a three-level page table setup. On
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* the i386, we use that, but "fold" the mid level into the top-level page
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* table, so that we physically have the same two-level page table as the
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* i386 mmu expects.
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*
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* This file contains the functions and defines necessary to modify and use
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* the i386 page table tree.
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*/
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#ifndef __ASSEMBLY__
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#include <asm/processor.h>
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#include <linux/threads.h>
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#include <asm/paravirt.h>
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#include <linux/bitops.h>
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#include <linux/list.h>
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#include <linux/spinlock.h>
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struct mm_struct;
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struct vm_area_struct;
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extern pgd_t swapper_pg_dir[1024];
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extern pgd_t initial_page_table[1024];
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extern pmd_t initial_pg_pmd[];
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void paging_init(void);
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void sync_initial_page_table(void);
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#ifdef CONFIG_X86_PAE
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# include <asm/pgtable-3level.h>
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#else
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# include <asm/pgtable-2level.h>
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#endif
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/* Clear a kernel PTE and flush it from the TLB */
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#define kpte_clear_flush(ptep, vaddr) \
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do { \
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pte_clear(&init_mm, (vaddr), (ptep)); \
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flush_tlb_one_kernel((vaddr)); \
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} while (0)
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#endif /* !__ASSEMBLY__ */
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/*
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* kern_addr_valid() is (1) for FLATMEM and (0) for SPARSEMEM
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*/
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#ifdef CONFIG_FLATMEM
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#define kern_addr_valid(addr) (1)
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#else
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#define kern_addr_valid(kaddr) (0)
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#endif
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/*
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* This is used to calculate the .brk reservation for initial pagetables.
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* Enough space is reserved to allocate pagetables sufficient to cover all
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* of LOWMEM_PAGES, which is an upper bound on the size of the direct map of
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* lowmem.
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*
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* With PAE paging (PTRS_PER_PMD > 1), we allocate PTRS_PER_PGD == 4 pages for
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* the PMD's in addition to the pages required for the last level pagetables.
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*/
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#if PTRS_PER_PMD > 1
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#define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
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#else
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#define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
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#endif
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/*
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* Number of possible pages in the lowmem region.
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*
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* We shift 2 by 31 instead of 1 by 32 to the left in order to avoid a
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* gas warning about overflowing shift count when gas has been compiled
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* with only a host target support using a 32-bit type for internal
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* representation.
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*/
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#define LOWMEM_PAGES ((((_ULL(2)<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
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#endif /* _ASM_X86_PGTABLE_32_H */
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