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    Subject[PATCH 4.9 01/28] arm64: entry: Restore tramp_map_kernel ISB
    Date
    From: James Morse <james.morse@arm.com>

    Summit reports that the BHB backports for v4.9 prevent vulnerable
    platforms from booting when CONFIG_RANDOMIZE_BASE is enabled.

    This is because the trampoline code takes a translation fault when
    accessing the data page, because the TTBR write hasn't been completed
    by an ISB before the access is made.

    Upstream has a complex erratum workaround for QCOM_FALKOR_E1003 in
    this area, which removes the ISB when the workaround has been applied.
    v4.9 lacks this workaround, but should still have the ISB.

    Restore the barrier.

    Fixes: aee10c2dd013 ("arm64: entry: Add macro for reading symbol addresses from the trampoline")
    Reported-by: Sumit Gupta <sumitg@nvidia.com>
    Tested-by: Sumit Gupta <sumitg@nvidia.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: James Morse <james.morse@arm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/arm64/kernel/entry.S | 1 +
    1 file changed, 1 insertion(+)

    --- a/arch/arm64/kernel/entry.S
    +++ b/arch/arm64/kernel/entry.S
    @@ -964,6 +964,7 @@ __ni_sys_trace:
    b .
    2:
    tramp_map_kernel x30
    + isb
    tramp_data_read_var x30, vectors
    prfm plil1strm, [x30, #(1b - \vector_start)]
    msr vbar_el1, x30

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