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The asm code that creates the initial ID map is rather intricate and hard to follow. This is problematic because it makes adding support for things like LPA2 or WXN more difficult than necessary. Also, it is parameterized like the rest of the MM code to run with a configurable number of levels, which is rather pointless, given that all AArch64 CPUs implement support for 48-bit virtual addressing, and that many systems exist with DRAM located outside of the 39-bit addressable range, which is the only smaller VA size that is widely used, and we need additional tricks to make things work in that combination. So let's bite the bullet, and rip out all the asm macros, and fiddly code, and replace it with a C implementation based on the newly added routines for creating the early kernel VA mappings. And while at it, create the initial ID map based on 48-bit virtual addressing as well, regardless of the number of configured levels for the kernel proper. Note that this code may execute with the MMU and caches disabled, and is therefore not permitted to make unaligned accesses. This shouldn't generally happen in any case for the algorithm as implemented, but to be sure, let's pass -mstrict-align to the compiler just in case. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20240214122845.2033971-66-ardb+git@google.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
88 lines
3.4 KiB
C
88 lines
3.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Kernel page table mapping
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*
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* Copyright (C) 2015 ARM Ltd.
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*/
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#ifndef __ASM_KERNEL_PGTABLE_H
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#define __ASM_KERNEL_PGTABLE_H
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#include <asm/boot.h>
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#include <asm/pgtable-hwdef.h>
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#include <asm/sparsemem.h>
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/*
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* The physical and virtual addresses of the start of the kernel image are
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* equal modulo 2 MiB (per the arm64 booting.txt requirements). Hence we can
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* use section mapping with 4K (section size = 2M) but not with 16K (section
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* size = 32M) or 64K (section size = 512M).
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*/
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#if defined(PMD_SIZE) && PMD_SIZE <= MIN_KIMG_ALIGN
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#define SWAPPER_BLOCK_SHIFT PMD_SHIFT
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#define SWAPPER_SKIP_LEVEL 1
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#else
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#define SWAPPER_BLOCK_SHIFT PAGE_SHIFT
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#define SWAPPER_SKIP_LEVEL 0
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#endif
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#define SWAPPER_BLOCK_SIZE (UL(1) << SWAPPER_BLOCK_SHIFT)
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#define SWAPPER_TABLE_SHIFT (SWAPPER_BLOCK_SHIFT + PAGE_SHIFT - 3)
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#define SWAPPER_PGTABLE_LEVELS (CONFIG_PGTABLE_LEVELS - SWAPPER_SKIP_LEVEL)
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#define INIT_IDMAP_PGTABLE_LEVELS (IDMAP_LEVELS - SWAPPER_SKIP_LEVEL)
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#define IDMAP_VA_BITS 48
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#define IDMAP_LEVELS ARM64_HW_PGTABLE_LEVELS(IDMAP_VA_BITS)
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#define IDMAP_ROOT_LEVEL (4 - IDMAP_LEVELS)
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/*
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* A relocatable kernel may execute from an address that differs from the one at
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* which it was linked. In the worst case, its runtime placement may intersect
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* with two adjacent PGDIR entries, which means that an additional page table
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* may be needed at each subordinate level.
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*/
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#define EXTRA_PAGE __is_defined(CONFIG_RELOCATABLE)
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#define SPAN_NR_ENTRIES(vstart, vend, shift) \
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((((vend) - 1) >> (shift)) - ((vstart) >> (shift)) + 1)
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#define EARLY_ENTRIES(vstart, vend, shift, add) \
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(SPAN_NR_ENTRIES(vstart, vend, shift) + (add))
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#define EARLY_LEVEL(lvl, lvls, vstart, vend, add) \
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(lvls > lvl ? EARLY_ENTRIES(vstart, vend, SWAPPER_BLOCK_SHIFT + lvl * (PAGE_SHIFT - 3), add) : 0)
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#define EARLY_PAGES(lvls, vstart, vend, add) (1 /* PGDIR page */ \
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+ EARLY_LEVEL(3, (lvls), (vstart), (vend), add) /* each entry needs a next level page table */ \
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+ EARLY_LEVEL(2, (lvls), (vstart), (vend), add) /* each entry needs a next level page table */ \
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+ EARLY_LEVEL(1, (lvls), (vstart), (vend), add))/* each entry needs a next level page table */
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#define INIT_DIR_SIZE (PAGE_SIZE * (EARLY_PAGES(SWAPPER_PGTABLE_LEVELS, KIMAGE_VADDR, _end, EXTRA_PAGE) \
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+ EARLY_SEGMENT_EXTRA_PAGES))
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#define INIT_IDMAP_DIR_PAGES (EARLY_PAGES(INIT_IDMAP_PGTABLE_LEVELS, KIMAGE_VADDR, _end, 1))
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#define INIT_IDMAP_DIR_SIZE ((INIT_IDMAP_DIR_PAGES + EARLY_IDMAP_EXTRA_PAGES) * PAGE_SIZE)
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#define INIT_IDMAP_FDT_PAGES (EARLY_PAGES(INIT_IDMAP_PGTABLE_LEVELS, 0UL, UL(MAX_FDT_SIZE), 1) - 1)
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#define INIT_IDMAP_FDT_SIZE ((INIT_IDMAP_FDT_PAGES + EARLY_IDMAP_EXTRA_FDT_PAGES) * PAGE_SIZE)
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/* The number of segments in the kernel image (text, rodata, inittext, initdata, data+bss) */
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#define KERNEL_SEGMENT_COUNT 5
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#if SWAPPER_BLOCK_SIZE > SEGMENT_ALIGN
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#define EARLY_SEGMENT_EXTRA_PAGES (KERNEL_SEGMENT_COUNT + 1)
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/*
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* The initial ID map consists of the kernel image, mapped as two separate
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* segments, and may appear misaligned wrt the swapper block size. This means
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* we need 3 additional pages. The DT could straddle a swapper block boundary,
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* so it may need 2.
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*/
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#define EARLY_IDMAP_EXTRA_PAGES 3
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#define EARLY_IDMAP_EXTRA_FDT_PAGES 2
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#else
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#define EARLY_SEGMENT_EXTRA_PAGES 0
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#define EARLY_IDMAP_EXTRA_PAGES 0
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#define EARLY_IDMAP_EXTRA_FDT_PAGES 0
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#endif
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#endif /* __ASM_KERNEL_PGTABLE_H */
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