gistfile1.txt

arm (V7M), um
    user_mode(pt_regs) does not distinguish between user and kernel execution.

alpha, arc, parisc, powerpc (non-PF_KTHREAD), x86 (PF_KTHREAD)
    pt_regs is zeroed using a memset call, which is interpreted as kernel mode
    by the user_mode macro.

arm (non-V7M), arm64, hexagon, m68k, microblaze, nios2, riscv, s390, sh
    The status register in pt_regs is explicitly set to a kernel mode value.

csky, loongarch, mips, mips, sparc (32-bit)
    The status register in pt_regs is initialized from the current _hardware_
    status register, similar to an interrupt in kernel mode.

openrisc, sparc (64-bit)
    pt_regs is zeroed using a memset call, which is interpreted as user mode
    by the user_mode macro.

powerpc (PF_KTHREAD)
    task_pt_regs returns a NULL pointer for the new thread; user_mode will
    fault if called.

x86 (non-PF_KTHREAD)
    pt_regs are copied from the current thread, so user mode helpers started
    from kthreadd will appear as kernel mode.

xtensa
    The status register of the child pt_regs is not initialized; behavior 
    depends on memory contents returned from the stack allocator.