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    Subject[PATCH v5 14/15] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0
    Date
    Allow systems with mismatched 32-bit support at EL0 to run 32-bit
    applications based on a new kernel parameter.

    Signed-off-by: Will Deacon <will@kernel.org>
    ---
    Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++
    arch/arm64/kernel/cpufeature.c | 7 +++++++
    2 files changed, 15 insertions(+)

    diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
    index 44fde25bb221..9d191e6e020b 100644
    --- a/Documentation/admin-guide/kernel-parameters.txt
    +++ b/Documentation/admin-guide/kernel-parameters.txt
    @@ -289,6 +289,14 @@
    do not want to use tracing_snapshot_alloc() as it needs
    to be done where GFP_KERNEL allocations are allowed.

    + allow_mismatched_32bit_el0 [ARM64]
    + Allow execve() of 32-bit applications and setting of the
    + PER_LINUX32 personality on systems where only a strict
    + subset of the CPUs support 32-bit EL0. When this
    + parameter is present, the set of CPUs supporting 32-bit
    + EL0 is indicated by /sys/devices/system/cpu/aarch32_el0
    + and hot-unplug operations may be restricted.
    +
    amd_iommu= [HW,X86-64]
    Pass parameters to the AMD IOMMU driver in the system.
    Possible values are:
    diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
    index 08b558a221b7..fea0f213d55c 100644
    --- a/arch/arm64/kernel/cpufeature.c
    +++ b/arch/arm64/kernel/cpufeature.c
    @@ -1291,6 +1291,13 @@ const struct cpumask *system_32bit_el0_cpumask(void)
    return cpu_possible_mask;
    }

    +static int __init parse_32bit_el0_param(char *str)
    +{
    + allow_mismatched_32bit_el0 = true;
    + return 0;
    +}
    +early_param("allow_mismatched_32bit_el0", parse_32bit_el0_param);
    +
    static ssize_t aarch32_el0_show(struct device *dev,
    struct device_attribute *attr, char *buf)
    {
    --
    2.29.2.576.ga3fc446d84-goog
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