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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
80 lines
2.3 KiB
C
80 lines
2.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_PAGE_32_DEFS_H
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#define _ASM_X86_PAGE_32_DEFS_H
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#include <linux/const.h>
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/*
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* This handles the memory map.
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*
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* A __PAGE_OFFSET of 0xC0000000 means that the kernel has
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* a virtual address space of one gigabyte, which limits the
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* amount of physical memory you can use to about 950MB.
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*
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* If you want more physical memory than this then see the CONFIG_HIGHMEM4G
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* and CONFIG_HIGHMEM64G options in the kernel configuration.
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*/
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#define __PAGE_OFFSET_BASE _AC(CONFIG_PAGE_OFFSET, UL)
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#define __PAGE_OFFSET __PAGE_OFFSET_BASE
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#define __START_KERNEL_map __PAGE_OFFSET
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#define THREAD_SIZE_ORDER 1
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#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)
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#define IRQ_STACK_SIZE THREAD_SIZE
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#define N_EXCEPTION_STACKS 1
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#ifdef CONFIG_X86_PAE
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/*
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* This is beyond the 44 bit limit imposed by the 32bit long pfns,
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* but we need the full mask to make sure inverted PROT_NONE
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* entries have all the host bits set in a guest.
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* The real limit is still 44 bits.
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*/
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#define __PHYSICAL_MASK_SHIFT 52
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#define __VIRTUAL_MASK_SHIFT 32
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#else /* !CONFIG_X86_PAE */
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#define __PHYSICAL_MASK_SHIFT 32
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#define __VIRTUAL_MASK_SHIFT 32
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#endif /* CONFIG_X86_PAE */
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/*
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* User space process size: 3GB (default).
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*/
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#define IA32_PAGE_OFFSET __PAGE_OFFSET
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#define TASK_SIZE __PAGE_OFFSET
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#define TASK_SIZE_LOW TASK_SIZE
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#define TASK_SIZE_MAX TASK_SIZE
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#define DEFAULT_MAP_WINDOW TASK_SIZE
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#define STACK_TOP TASK_SIZE
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#define STACK_TOP_MAX STACK_TOP
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/*
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* In spite of the name, KERNEL_IMAGE_SIZE is a limit on the maximum virtual
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* address for the kernel image, rather than the limit on the size itself. On
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* 32-bit, this is not a strict limit, but this value is used to limit the
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* link-time virtual address range of the kernel, and by KASLR to limit the
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* randomized address from which the kernel is executed. A relocatable kernel
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* can be loaded somewhat higher than KERNEL_IMAGE_SIZE as long as enough space
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* remains for the vmalloc area.
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*/
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#define KERNEL_IMAGE_SIZE (512 * 1024 * 1024)
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#ifndef __ASSEMBLY__
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/*
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* This much address space is reserved for vmalloc() and iomap()
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* as well as fixmap mappings.
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*/
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extern unsigned int __VMALLOC_RESERVE;
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extern int sysctl_legacy_va_layout;
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extern void find_low_pfn_range(void);
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extern void setup_bootmem_allocator(void);
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#endif /* !__ASSEMBLY__ */
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#endif /* _ASM_X86_PAGE_32_DEFS_H */
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