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408a43b6c9
[ Commit 9c55461040 upstream ]
Currently, the EFI stub invokes the EFI memory attributes protocol to
strip any NX restrictions from the entire loaded kernel, resulting in
all code and data being mapped read-write-execute.
The point of the EFI memory attributes protocol is to remove the need
for all memory allocations to be mapped with both write and execute
permissions by default, and make it the OS loader's responsibility to
transition data mappings to code mappings where appropriate.
Even though the UEFI specification does not appear to leave room for
denying memory attribute changes based on security policy, let's be
cautious and avoid relying on the ability to create read-write-execute
mappings. This is trivially achievable, given that the amount of kernel
code executing via the firmware's 1:1 mapping is rather small and
limited to the .head.text region. So let's drop the NX restrictions only
on that subregion, but not before remapping it as read-only first.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
94 lines
2.6 KiB
C
94 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_text_size;
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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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extern struct boot_params *boot_params_ptr;
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#endif
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#endif /* _ASM_X86_BOOT_H */
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