• Ard Biesheuvel's avatar
    efi/x86: Fix incorrect invocation of PciIo->Attributes() · 2e6eb40c
    Ard Biesheuvel authored
    The following commit:
    
      2c3625cb ("efi/x86: Fold __setup_efi_pci32() and __setup_efi_pci64() into one function")
    
    ... merged the two versions of __setup_efi_pciXX(), without taking into
    account that the 32-bit version used a rather dodgy trick to pass an
    immediate 0 constant as argument for a uint64_t parameter.
    
    The issue is caused by the fact that on x86, UEFI protocol method calls
    are redirected via struct efi_config::call(), which is a variadic function,
    and so the compiler has to infer the types of the parameters from the
    arguments rather than from the prototype.
    
    As the 32-bit x86 calling convention passes arguments via the stack,
    passing the unqualified constant 0 twice is the same as passing 0ULL,
    which is why the 32-bit code in __setup_efi_pci32() contained the
    following call:
    
      status = efi_early->call(pci->attributes, pci,
                               EfiPciIoAttributeOperationGet, 0, 0,
                               &attributes);
    
    to invoke this UEFI protocol method:
    
      typedef
      EFI_STATUS
      (EFIAPI *EFI_PCI_IO_PROTOCOL_ATTRIBUTES) (
        IN  EFI_PCI_IO_PROTOCOL                     *This,
        IN  EFI_PCI_IO_PROTOCOL_ATTRIBUTE_OPERATION Operation,
        IN  UINT64                                  Attributes,
        OUT UINT64                                  *Result OPTIONAL
        );
    
    After the merge, we inadvertently ended up with this version for both
    32-bit and 64-bit builds, breaking the latter.
    
    So replace the two zeroes with the explicitly typed constant 0ULL,
    which works as expected on both 32-bit and 64-bit builds.
    
    Wilfried tested the 64-bit build, and I checked the generated assembly
    of a 32-bit build with and without this patch, and they are identical.
    Reported-by: default avatarWilfried Klaebe <linux-kernel@lebenslange-mailadresse.de>
    Tested-by: default avatarWilfried Klaebe <linux-kernel@lebenslange-mailadresse.de>
    Signed-off-by: default avatarArd 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: hdegoede@redhat.com
    Cc: linux-efi@vger.kernel.org
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    2e6eb40c
eboot.c 26.6 KB