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[ Upstream commit 4e46c2a956 ]
The UEFI spec revision 2.7 errata A section 8.4 has the following to
say about the virtual memory runtime services:
"This section contains function definitions for the virtual memory
support that may be optionally used by an operating system at runtime.
If an operating system chooses to make EFI runtime service calls in a
virtual addressing mode instead of the flat physical mode, then the
operating system must use the services in this section to switch the
EFI runtime services from flat physical addressing to virtual
addressing."
So it is pretty clear that calling SetVirtualAddressMap() is entirely
optional, and so there is no point in doing so unless it achieves
anything useful for us.
This is not the case for 64-bit ARM. The identity mapping used by the
firmware is arbitrarily converted into another permutation of userland
addresses (i.e., bits [63:48] cleared), and the runtime code could easily
deal with the original layout in exactly the same way as it deals with
the converted layout. However, due to constraints related to page size
differences if the OS is not running with 4k pages, and related to
systems that may expose the individual sections of PE/COFF runtime
modules as different memory regions, creating the virtual layout is a
bit fiddly, and requires us to sort the memory map and reason about
adjacent regions with identical memory types etc etc.
So the obvious fix is to stop calling SetVirtualAddressMap() altogether
on arm64 systems. However, to avoid surprises, which are notoriously
hard to diagnose when it comes to OS<->firmware interactions, let's
start by making it an opt-out feature, and implement support for the
'efi=novamap' kernel command line parameter on ARM and arm64 systems.
( Note that 32-bit ARM generally does require SetVirtualAddressMap() to be
used, given that the physical memory map and the kernel virtual address
map are not guaranteed to be non-overlapping like on arm64. However,
having support for efi=novamap,noruntime on 32-bit ARM, combined with
the recently proposed support for earlycon=efifb, is likely to be useful
to diagnose boot issues on such systems if they have no accessible serial
port. )
Tested-by: Jeffrey Hugo <jhugo@codeaurora.org>
Tested-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Tested-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Alexander Graf <agraf@suse.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Jones <pjones@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20190202094119.13230-8-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
68 lines
2.3 KiB
C
68 lines
2.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _DRIVERS_FIRMWARE_EFI_EFISTUB_H
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#define _DRIVERS_FIRMWARE_EFI_EFISTUB_H
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/* error code which can't be mistaken for valid address */
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#define EFI_ERROR (~0UL)
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/*
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* __init annotations should not be used in the EFI stub, since the code is
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* either included in the decompressor (x86, ARM) where they have no effect,
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* or the whole stub is __init annotated at the section level (arm64), by
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* renaming the sections, in which case the __init annotation will be
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* redundant, and will result in section names like .init.init.text, and our
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* linker script does not expect that.
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*/
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#undef __init
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/*
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* Allow the platform to override the allocation granularity: this allows
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* systems that have the capability to run with a larger page size to deal
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* with the allocations for initrd and fdt more efficiently.
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*/
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#ifndef EFI_ALLOC_ALIGN
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#define EFI_ALLOC_ALIGN EFI_PAGE_SIZE
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#endif
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extern int __pure nokaslr(void);
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extern int __pure is_quiet(void);
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extern int __pure novamap(void);
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#define pr_efi(sys_table, msg) do { \
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if (!is_quiet()) efi_printk(sys_table, "EFI stub: "msg); \
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} while (0)
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#define pr_efi_err(sys_table, msg) efi_printk(sys_table, "EFI stub: ERROR: "msg)
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void efi_char16_printk(efi_system_table_t *, efi_char16_t *);
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unsigned long get_dram_base(efi_system_table_t *sys_table_arg);
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efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
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void *handle,
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unsigned long *new_fdt_addr,
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unsigned long max_addr,
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u64 initrd_addr, u64 initrd_size,
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char *cmdline_ptr,
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unsigned long fdt_addr,
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unsigned long fdt_size);
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void *get_fdt(efi_system_table_t *sys_table, unsigned long *fdt_size);
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void efi_get_virtmap(efi_memory_desc_t *memory_map, unsigned long map_size,
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unsigned long desc_size, efi_memory_desc_t *runtime_map,
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int *count);
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efi_status_t efi_get_random_bytes(efi_system_table_t *sys_table,
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unsigned long size, u8 *out);
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efi_status_t efi_random_alloc(efi_system_table_t *sys_table_arg,
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unsigned long size, unsigned long align,
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unsigned long *addr, unsigned long random_seed);
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efi_status_t check_platform_features(efi_system_table_t *sys_table_arg);
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efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg);
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#endif
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