kernel/linux.git/arch/arm64/include/asm/kernel-pgtable.h, branch v6.6.131

arm64: fix build warning for ARM64_MEMSTART_SHIFT

2023-08-04T16:19:44+00:00

When building with W=1, the following warning occurs. arch/arm64/include/asm/kernel-pgtable.h:129:41: error: "PUD_SHIFT" is not defined, evaluates to 0 [-Werror=undef] 129 | #define ARM64_MEMSTART_SHIFT PUD_SHIFT | ^~~~~~~~~ arch/arm64/include/asm/kernel-pgtable.h:142:5: note: in expansion of macro ‘ARM64_MEMSTART_SHIFT’ 142 | #if ARM64_MEMSTART_SHIFT < SECTION_SIZE_BITS | ^~~~~~~~~~~~~~~~~~~~ The generic PUD_SHIFT was defined in include/asm-generic/pgtable-nopud.h, however the #ifndef __ASSEMBLY__ guard in this header file makes it unavailable for assembly files. While someone .S file include the , the build warning would occur. Now move the macro ARM64_MEMSTART_SHIFT and ARM64_MEMSTART_ALIGN to arch/arm64/mm/init.c where it is used only, to avoid this issue. Signed-off-by: Zhang Jianhua Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20230804075615.3334756-1-chris.zjh@huawei.com Signed-off-by: Will Deacon

arm64: add PTE_UXN/PTE_WRITE to SWAPPER_*_FLAGS

2023-06-06T15:52:41+00:00

With PIE enabled, the swapper PTEs would have a Permission Indirection Index (PIIndex) of 0. A PIIndex of 0 is not currently used by any other PTEs. To avoid using index 0 specifically for the swapper PTEs, mark them as PTE_UXN and PTE_WRITE, so that they map to a PAGE_KERNEL_EXEC equivalent. This also adds PTE_WRITE to KPTI_NG_PTE_FLAGS, which was tested by booting with kpti=on. Signed-off-by: Joey Gouly Cc: Will Deacon Cc: Mark Rutland Link: https://lore.kernel.org/r/20230606145859.697944-12-joey.gouly@arm.com Signed-off-by: Catalin Marinas

arm64: mm: always map fixmap at page granularity

2023-04-11T17:55:28+00:00

Today the fixmap code largely maps elements at PAGE_SIZE granularity, but we special-case the FDT mapping such that it can be mapped with 2M block mappings when 4K pages are in use. The original rationale for this was simplicity, but it has some unfortunate side-effects, and complicates portions of the fixmap code (i.e. is not so simple after all). The FDT can be up to 2M in size but is only required to have 8-byte alignment, and so it may straddle a 2M boundary. Thus when using 2M block mappings we may map up to 4M of memory surrounding the FDT. This is unfortunate as most of that memory will be unrelated to the FDT, and any pages which happen to share a 2M block with the FDT will by mapped with Normal Write-Back Cacheable attributes, which might not be what we want elsewhere (e.g. for carve-outs using Non-Cacheable attributes). The logic to handle mapping the FDT with 2M blocks requires some special cases in the fixmap code, and ties it to the early page table configuration by virtue of the SWAPPER_TABLE_SHIFT and SWAPPER_BLOCK_SIZE constants used to determine the granularity used to map the FDT. This patch simplifies the FDT logic and removes the unnecessary mappings of surrounding pages by always mapping the FDT at page granularity as with all other fixmap mappings. To do so we statically reserve multiple PTE tables to cover the fixmap VA range. Since the FDT can be at most 2M, for 4K pages we only need to allocate a single additional PTE table, and for 16K and 64K pages the existing single PTE table is sufficient. The PTE table allocation scales with the number of slots reserved in the fixmap, and so this also makes it easier to add more fixmap entries if we require those in future. Our VA layout means that the fixmap will always fall within a single PMD table (and consequently, within a single PUD/P4D/PGD entry), which we can verify at compile time with a static_assert(). With that assert a number of runtime warnings become impossible, and are removed. I've boot-tested this patch with both 4K and 64K pages. Signed-off-by: Mark Rutland Cc: Anshuman Khandual Cc: Ard Biesheuvel Cc: Catalin Marinas Cc: Ryan Roberts Cc: Will Deacon Reviewed-by: Ryan Roberts Link: https://lore.kernel.org/r/20230406152759.4164229-4-mark.rutland@arm.com Signed-off-by: Will Deacon

arm64/mm: Drop ARM64_KERNEL_USES_PMD_MAPS

2022-11-08T13:59:36+00:00

Currently ARM64_KERNEL_USES_PMD_MAPS is an unnecessary abstraction. Kernel mapping at PMD (aka huge page aka block) level, is only applicable with 4K base page, which makes it 2MB aligned, a necessary requirement for linear mapping and physical memory start address. This can be easily achieved by directly checking against base page size itself. This drops off the macro ARM64_KERNE_USES_PMD_MAPS which is redundant. Cc: Catalin Marinas Cc: Will Deacon Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Anshuman Khandual Link: https://lore.kernel.org/r/20221108034406.2950071-1-anshuman.khandual@arm.com Signed-off-by: Will Deacon

arm64: mm: Reserve enough pages for the initial ID map

2022-09-01T11:02:39+00:00

The logic that conditionally allocates one additional page at each swapper page table level if KASLR is enabled is also applied to the initial ID map, now that we have started using the same set of macros to allocate the space for it. However, the placement of the kernel in physical memory might result in additional pages being needed at any level, even if KASLR is disabled in the build. So account for this in the computation. Fixes: c3cee924bd85 ("arm64: head: cover entire kernel image in initial ID map") Signed-off-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20220826164800.2059148-1-ardb@kernel.org Signed-off-by: Will Deacon

arm64: head: create a temporary FDT mapping in the initial ID map

2022-06-24T16:18:10+00:00

We need to access the DT very early to get at the command line and the KASLR seed, which currently means we rely on some hacks to call into the kernel before really calling into the kernel, which is undesirable. So instead, let's create a mapping for the FDT in the initial ID map, which is feasible now that it has been extended to cover more than a single page or block, and can be updated in place to remap other output addresses. Signed-off-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20220624150651.1358849-15-ardb@kernel.org Signed-off-by: Will Deacon

arm64: head: cover entire kernel image in initial ID map

2022-06-24T16:18:10+00:00

As a first step towards avoiding the need to create, tear down and recreate the kernel virtual mapping with MMU and caches disabled, start by expanding the ID map so it covers the page tables as well as all executable code. This will allow us to populate the page tables with the MMU and caches on, and call KASLR init code before setting up the virtual mapping. Since this ID map is only needed at boot, create it as a temporary set of page tables, and populate the permanent ID map after enabling the MMU and caches. While at it, switch to read-only attributes for the where possible, as writable permissions are only needed for the initial kernel page tables. Note that on 4k granule configurations, the permanent ID map will now be reduced to a single page rather than a 2M block mapping. Signed-off-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20220624150651.1358849-13-ardb@kernel.org Signed-off-by: Will Deacon

arm64: head: avoid over-mapping in map_memory

2021-08-24T15:44:23+00:00

The `compute_indices` and `populate_entries` macros operate on inclusive bounds, and thus the `map_memory` macro which uses them also operates on inclusive bounds. We pass `_end` and `_idmap_text_end` to `map_memory`, but these are exclusive bounds, and if one of these is sufficiently aligned (as a result of kernel configuration, physical placement, and KASLR), then: * In `compute_indices`, the computed `iend` will be in the page/block *after* the final byte of the intended mapping. * In `populate_entries`, an unnecessary entry will be created at the end of each level of table. At the leaf level, this entry will map up to SWAPPER_BLOCK_SIZE bytes of physical addresses that we did not intend to map. As we may map up to SWAPPER_BLOCK_SIZE bytes more than intended, we may violate the boot protocol and map physical address past the 2MiB-aligned end address we are permitted to map. As we map these with Normal memory attributes, this may result in further problems depending on what these physical addresses correspond to. The final entry at each level may require an additional table at that level. As EARLY_ENTRIES() calculates an inclusive bound, we allocate enough memory for this. Avoid the extraneous mapping by having map_memory convert the exclusive end address to an inclusive end address by subtracting one, and do likewise in EARLY_ENTRIES() when calculating the number of required tables. For clarity, comments are updated to more clearly document which boundaries the macros operate on. For consistency with the other macros, the comments in map_memory are also updated to describe `vstart` and `vend` as virtual addresses. Fixes: 0370b31e4845 ("arm64: Extend early page table code to allow for larger kernels") Cc: # 4.16.x Signed-off-by: Mark Rutland Cc: Anshuman Khandual Cc: Ard Biesheuvel Cc: Steve Capper Cc: Will Deacon Acked-by: Will Deacon Link: https://lore.kernel.org/r/20210823101253.55567-1-mark.rutland@arm.com Signed-off-by: Catalin Marinas

arm64/mm: Rename ARM64_SWAPPER_USES_SECTION_MAPS

2021-06-21T17:22:23+00:00

ARM64_SWAPPER_USES_SECTION_MAPS implies that a PMD level huge page mappings are used for swapper, idmap and vmemmap. Lets make it PMD explicit removing any possible confusion with generic memory sections and also bit generic as it's applicable for idmap and vmemmap mappings as well. Hence rename it as ARM64_KERNEL_USES_PMD_MAPS instead. Cc: Catalin Marinas Cc: Will Deacon Cc: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Anshuman Khandual Acked-by: Catalin Marinas Link: https://lore.kernel.org/r/1623991622-24294-1-git-send-email-anshuman.khandual@arm.com Signed-off-by: Will Deacon

arm64/mm: Drop SECTION_[SHIFT|SIZE|MASK]

2021-06-15T11:08:39+00:00

SECTION_[SHIFT|SIZE|MASK] are essentially PMD_[SHIFT|SIZE|MASK]. But these create confusion being similar to generic sparsemem memory sections, which are derived from SECTION_SIZE_BITS. Section references have always implied PMD level block mapping. Instead just use all PMD level macros which would make it explicit and also remove confusion with sparsmem memory sections. Cc: Catalin Marinas Cc: Will Deacon Cc: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Anshuman Khandual Reviewed-by: Gavin Shan Acked-by: Catalin Marinas Link: https://lore.kernel.org/r/1623658706-7182-1-git-send-email-anshuman.khandual@arm.com Signed-off-by: Will Deacon