arm64: permit ACPI core to map kernel memory used for table overrides (a509a66a) · Commits · 戴 / test

Jonathan reports that the strict policy for memory mapped by the ACPI core breaks the use case of passing ACPI table overrides via initramfs. This is due to the fact that the memory type used for loading the initramfs in memory is not recognized as a memory type that is typically used by firmware to pass firmware tables. Since the purpose of the strict policy is to ensure that no AML or other ACPI code can manipulate any memory that is used by the kernel to keep its internal state or the state of user tasks, we can relax the permission check, and allow mappings of memory that is reserved and marked as NOMAP via memblock, and therefore not covered by the linear mapping to begin with. Fixes: ("arm64/acpi: disallow AML memory opregions to access kernel memory") Fixes: ("arm64/acpi: disallow writeable AML opregion mapping for EFI code regions") Reported-by:

Jonathan Cameron <Jonathan.Cameron@huawei.com> Signed-off-by:

Ard Biesheuvel <ardb@kernel.org> Tested-by:

Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Sudeep Holla <sudeep.holla@arm.com> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Link: https://lore.kernel.org/r/20200929132522.18067-1-ardb@kernel.org Signed-off-by:

Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/acpi.c

+20 −2

Original line number	Diff line number	Diff line
		@@ -298,8 +298,21 @@ void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
		case EFI_BOOT_SERVICES_DATA:
		case EFI_CONVENTIONAL_MEMORY:
		case EFI_PERSISTENT_MEMORY:
		if (memblock_is_map_memory(phys) \|\|
		!memblock_is_region_memory(phys, size)) {
		pr_warn(FW_BUG "requested region covers kernel memory @ %pa\n", &phys);
		return NULL;
		}
		/*
		* Mapping kernel memory is permitted if the region in
		* question is covered by a single memblock with the
		* NOMAP attribute set: this enables the use of ACPI
		* table overrides passed via initramfs, which are
		* reserved in memory using arch_reserve_mem_area()
		* below. As this particular use case only requires
		* read access, fall through to the R/O mapping case.
		*/
		fallthrough;

		case EFI_RUNTIME_SERVICES_CODE:
		/*
		@@ -388,3 +401,8 @@ int apei_claim_sea(struct pt_regs *regs)

		return err;
		}

		void arch_reserve_mem_area(acpi_physical_address addr, size_t size)
		{
		memblock_mark_nomap(addr, size);
		}

include/linux/acpi.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -958,7 +958,7 @@ void acpi_os_set_prepare_extended_sleep(int (*func)(u8 sleep_state,
		acpi_status acpi_os_prepare_extended_sleep(u8 sleep_state,
		u32 val_a, u32 val_b);

		#ifdef CONFIG_X86
		#ifndef CONFIG_IA64
		void arch_reserve_mem_area(acpi_physical_address addr, size_t size);
		#else
		static inline void arch_reserve_mem_area(acpi_physical_address addr,

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