f530ee95b7
The decompressor has a hard limit on the number of page tables it can
allocate. This limit is defined at compile-time and will cause boot
failure if it is reached.
The kernel is very strict and calculates the limit precisely for the
worst-case scenario based on the current configuration. However, it is
easy to forget to adjust the limit when a new use-case arises. The
worst-case scenario is rarely encountered during sanity checks.
In the case of enabling 5-level paging, a use-case was overlooked. The
limit needs to be increased by one to accommodate the additional level.
This oversight went unnoticed until Aaron attempted to run the kernel
via kexec with 5-level paging and unaccepted memory enabled.
Update wost-case calculations to include 5-level paging.
To address this issue, let's allocate some extra space for page tables.
128K should be sufficient for any use-case. The logic can be simplified
by using a single value for all kernel configurations.
[ Also add a warning, should this memory run low - by Dave Hansen. ]
Fixes: 34bbb0009f3b ("x86/boot/compressed: Enable 5-level paging during decompression stage")
Reported-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915070221.10266-1-kirill.shutemov@linux.intel.com
91 lines
2.6 KiB
C
91 lines
2.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_BOOT_H
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#define _ASM_X86_BOOT_H
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#include <asm/pgtable_types.h>
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#include <uapi/asm/boot.h>
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/* Physical address where kernel should be loaded. */
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#define LOAD_PHYSICAL_ADDR ((CONFIG_PHYSICAL_START \
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+ (CONFIG_PHYSICAL_ALIGN - 1)) \
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& ~(CONFIG_PHYSICAL_ALIGN - 1))
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/* Minimum kernel alignment, as a power of two */
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#ifdef CONFIG_X86_64
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# define MIN_KERNEL_ALIGN_LG2 PMD_SHIFT
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#else
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# define MIN_KERNEL_ALIGN_LG2 (PAGE_SHIFT + THREAD_SIZE_ORDER)
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#endif
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#define MIN_KERNEL_ALIGN (_AC(1, UL) << MIN_KERNEL_ALIGN_LG2)
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#if (CONFIG_PHYSICAL_ALIGN & (CONFIG_PHYSICAL_ALIGN-1)) || \
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(CONFIG_PHYSICAL_ALIGN < MIN_KERNEL_ALIGN)
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# error "Invalid value for CONFIG_PHYSICAL_ALIGN"
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#endif
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#if defined(CONFIG_KERNEL_BZIP2)
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# define BOOT_HEAP_SIZE 0x400000
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#elif defined(CONFIG_KERNEL_ZSTD)
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/*
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* Zstd needs to allocate the ZSTD_DCtx in order to decompress the kernel.
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* The ZSTD_DCtx is ~160KB, so set the heap size to 192KB because it is a
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* round number and to allow some slack.
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*/
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# define BOOT_HEAP_SIZE 0x30000
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#else
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# define BOOT_HEAP_SIZE 0x10000
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#endif
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#ifdef CONFIG_X86_64
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# define BOOT_STACK_SIZE 0x4000
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/*
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* Used by decompressor's startup_32() to allocate page tables for identity
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* mapping of the 4G of RAM in 4-level paging mode:
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* - 1 level4 table;
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* - 1 level3 table;
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* - 4 level2 table that maps everything with 2M pages;
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*
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* The additional level5 table needed for 5-level paging is allocated from
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* trampoline_32bit memory.
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*/
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# define BOOT_INIT_PGT_SIZE (6*4096)
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/*
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* Total number of page tables kernel_add_identity_map() can allocate,
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* including page tables consumed by startup_32().
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*
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* Worst-case scenario:
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* - 5-level paging needs 1 level5 table;
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* - KASLR needs to map kernel, boot_params, cmdline and randomized kernel,
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* assuming all of them cross 256T boundary:
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* + 4*2 level4 table;
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* + 4*2 level3 table;
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* + 4*2 level2 table;
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* - X86_VERBOSE_BOOTUP needs to map the first 2M (video RAM):
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* + 1 level4 table;
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* + 1 level3 table;
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* + 1 level2 table;
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* Total: 28 tables
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*
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* Add 4 spare table in case decompressor touches anything beyond what is
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* accounted above. Warn if it happens.
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*/
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# define BOOT_PGT_SIZE_WARN (28*4096)
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# define BOOT_PGT_SIZE (32*4096)
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#else /* !CONFIG_X86_64 */
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# define BOOT_STACK_SIZE 0x1000
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#endif
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#ifndef __ASSEMBLY__
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extern unsigned int output_len;
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extern const unsigned long kernel_total_size;
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unsigned long decompress_kernel(unsigned char *outbuf, unsigned long virt_addr,
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void (*error)(char *x));
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#endif
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#endif /* _ASM_X86_BOOT_H */
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