• Will Deacon's avatar
    ARM: idmap: use idmap_pgd when setting up mm for reboot · 2c8951ab
    Will Deacon authored
    For soft-rebooting a system, it is necessary to map the MMU-off code
    with an identity mapping so that execution can continue safely once the
    MMU has been switched off.
    
    Currently, switch_mm_for_reboot takes out a 1:1 mapping from 0x0 to
    TASK_SIZE during reboot in the hope that the reset code lives at a
    physical address corresponding to a userspace virtual address.
    
    This patch modifies the code so that we switch to the idmap_pgd tables,
    which contain a 1:1 mapping of the cpu_reset code. This has the
    advantage of only remapping the code that we need and also means we
    don't need to worry about allocating a pgd from an atomic context in the
    case that the physical address of the cpu_reset code aliases with the
    virtual space used by the kernel.
    Acked-by: default avatarDave Martin <dave.martin@linaro.org>
    Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
    2c8951ab
idmap.c 2.72 KB