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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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20a004e7b0
In many cases, page tables can be accessed concurrently by either another CPU (due to things like fast gup) or by the hardware page table walker itself, which may set access/dirty bits. In such cases, it is important to use READ_ONCE/WRITE_ONCE when accessing page table entries so that entries cannot be torn, merged or subject to apparent loss of coherence due to compiler transformations. Whilst there are some scenarios where this cannot happen (e.g. pinned kernel mappings for the linear region), the overhead of using READ_ONCE /WRITE_ONCE everywhere is minimal and makes the code an awful lot easier to reason about. This patch consistently uses these macros in the arch code, as well as explicitly namespacing pointers to page table entries from the entries themselves by using adopting a 'p' suffix for the former (as is sometimes used elsewhere in the kernel source). Tested-by: Yury Norov <ynorov@caviumnetworks.com> Tested-by: Richard Ruigrok <rruigrok@codeaurora.org> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
129 lines
3.8 KiB
C
129 lines
3.8 KiB
C
/*
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* Extensible Firmware Interface
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*
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* Based on Extensible Firmware Interface Specification version 2.4
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*
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* Copyright (C) 2013, 2014 Linaro Ltd.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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#include <linux/efi.h>
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#include <linux/init.h>
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#include <asm/efi.h>
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/*
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* Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
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* executable, everything else can be mapped with the XN bits
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* set. Also take the new (optional) RO/XP bits into account.
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*/
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static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
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{
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u64 attr = md->attribute;
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u32 type = md->type;
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if (type == EFI_MEMORY_MAPPED_IO)
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return PROT_DEVICE_nGnRE;
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if (WARN_ONCE(!PAGE_ALIGNED(md->phys_addr),
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"UEFI Runtime regions are not aligned to 64 KB -- buggy firmware?"))
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/*
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* If the region is not aligned to the page size of the OS, we
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* can not use strict permissions, since that would also affect
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* the mapping attributes of the adjacent regions.
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*/
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return pgprot_val(PAGE_KERNEL_EXEC);
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/* R-- */
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if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
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(EFI_MEMORY_XP | EFI_MEMORY_RO))
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return pgprot_val(PAGE_KERNEL_RO);
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/* R-X */
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if (attr & EFI_MEMORY_RO)
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return pgprot_val(PAGE_KERNEL_ROX);
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/* RW- */
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if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
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EFI_MEMORY_XP) ||
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type != EFI_RUNTIME_SERVICES_CODE)
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return pgprot_val(PAGE_KERNEL);
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/* RWX */
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return pgprot_val(PAGE_KERNEL_EXEC);
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}
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/* we will fill this structure from the stub, so don't put it in .bss */
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struct screen_info screen_info __section(.data);
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int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
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{
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pteval_t prot_val = create_mapping_protection(md);
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bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
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md->type == EFI_RUNTIME_SERVICES_DATA);
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if (!PAGE_ALIGNED(md->phys_addr) ||
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!PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) {
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/*
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* If the end address of this region is not aligned to page
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* size, the mapping is rounded up, and may end up sharing a
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* page frame with the next UEFI memory region. If we create
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* a block entry now, we may need to split it again when mapping
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* the next region, and support for that is going to be removed
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* from the MMU routines. So avoid block mappings altogether in
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* that case.
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*/
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page_mappings_only = true;
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}
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create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
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md->num_pages << EFI_PAGE_SHIFT,
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__pgprot(prot_val | PTE_NG), page_mappings_only);
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return 0;
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}
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static int __init set_permissions(pte_t *ptep, pgtable_t token,
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unsigned long addr, void *data)
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{
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efi_memory_desc_t *md = data;
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pte_t pte = READ_ONCE(*ptep);
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if (md->attribute & EFI_MEMORY_RO)
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pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
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if (md->attribute & EFI_MEMORY_XP)
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pte = set_pte_bit(pte, __pgprot(PTE_PXN));
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set_pte(ptep, pte);
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return 0;
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}
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int __init efi_set_mapping_permissions(struct mm_struct *mm,
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efi_memory_desc_t *md)
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{
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BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
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md->type != EFI_RUNTIME_SERVICES_DATA);
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/*
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* Calling apply_to_page_range() is only safe on regions that are
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* guaranteed to be mapped down to pages. Since we are only called
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* for regions that have been mapped using efi_create_mapping() above
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* (and this is checked by the generic Memory Attributes table parsing
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* routines), there is no need to check that again here.
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*/
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return apply_to_page_range(mm, md->virt_addr,
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md->num_pages << EFI_PAGE_SHIFT,
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set_permissions, md);
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}
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/*
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* UpdateCapsule() depends on the system being shutdown via
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* ResetSystem().
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*/
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bool efi_poweroff_required(void)
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{
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return efi_enabled(EFI_RUNTIME_SERVICES);
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}
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