efi/x86: Fix mixed mode reboot loop by removing pointless call to PciIo->Attributes()
Hans de Goede reported that his mixed EFI mode Bay Trail tablet would not boot at all any more, but enter a reboot loop without any logs printed by the kernel. Unbreak 64-bit Linux/x86 on 32-bit UEFI: When it was first introduced, the EFI stub code that copies the contents of PCI option ROMs originally only intended to do so if the EFI_PCI_IO_ATTRIBUTE_EMBEDDED_ROM attribute was *not* set. The reason was that the UEFI spec permits PCI option ROM images to be provided by the platform directly, rather than via the ROM BAR, and in this case, the OS can only access them at runtime if they are preserved at boot time by copying them from the areas described by PciIo->RomImage and PciIo->RomSize. However, it implemented this check erroneously, as can be seen in commit:dd5fc854de
("EFI: Stash ROMs if they're not in the PCI BAR") which introduced: if (!attributes & EFI_PCI_IO_ATTRIBUTE_EMBEDDED_ROM) continue; and given that the numeric value of EFI_PCI_IO_ATTRIBUTE_EMBEDDED_ROM is 0x4000, this condition never becomes true, and so the option ROMs were copied unconditionally. This was spotted and 'fixed' by commit:886d751a2e
("x86, efi: correct precedence of operators in setup_efi_pci") but inadvertently inverted the logic at the same time, defeating the purpose of the code, since it now only preserves option ROM images that can be read from the ROM BAR as well. Unsurprisingly, this broke some systems, and so the check was removed entirely in the following commit:739701888f
("x86, efi: remove attribute check from setup_efi_pci") It is debatable whether this check should have been included in the first place, since the option ROM image provided to the UEFI driver by the firmware may be different from the one that is actually present in the card's flash ROM, and so whatever PciIo->RomImage points at should be preferred regardless of whether the attribute is set. As this was the only use of the attributes field, we can remove the call to PciIo->Attributes() entirely, which is especially nice because its prototype involves uint64_t type by-value arguments which the EFI mixed mode has trouble dealing with. Any mixed mode system with PCI is likely to be affected. Tested-by: Wilfried Klaebe <linux-kernel@lebenslange-mailadresse.de> Tested-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Matt Fleming <matt@codeblueprint.co.uk> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/20180711090235.9327-2-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -114,18 +114,12 @@ __setup_efi_pci(efi_pci_io_protocol_t *pci, struct pci_setup_rom **__rom)
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struct pci_setup_rom *rom = NULL;
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efi_status_t status;
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unsigned long size;
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uint64_t attributes, romsize;
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uint64_t romsize;
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void *romimage;
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status = efi_call_proto(efi_pci_io_protocol, attributes, pci,
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EfiPciIoAttributeOperationGet, 0ULL,
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&attributes);
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if (status != EFI_SUCCESS)
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return status;
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/*
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* Some firmware images contain EFI function pointers at the place where the
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* romimage and romsize fields are supposed to be. Typically the EFI
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* Some firmware images contain EFI function pointers at the place where
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* the romimage and romsize fields are supposed to be. Typically the EFI
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* code is mapped at high addresses, translating to an unrealistically
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* large romsize. The UEFI spec limits the size of option ROMs to 16
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* MiB so we reject any ROMs over 16 MiB in size to catch this.
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