xref: /gem5/src/arch/x86/isa/insts/romutil.py

# Copyright (c) 2008 The Regents of The University of Michigan
# All rights reserved.
#
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# neither the name of the copyright holders nor the names of its
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# this software without specific prior written permission.
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# Authors: Gabe Black

microcode = '''
def rom
{
    # This vectors the CPU into an interrupt handler in long mode.
    # On entry, t1 is set to the vector of the interrupt and t7 is the current
    # ip. We need that because rdip returns the next ip.
    extern longModeInterrupt:

    #
    # Get the 64 bit interrupt or trap gate descriptor from the IDT
    #

    # Load the gate descriptor from the IDT
    slli t4, t1, 4, dataSize=8
    ld t2, idtr, [1, t0, t4], 8, dataSize=8, addressSize=8
    ld t4, idtr, [1, t0, t4], dataSize=8, addressSize=8

    # Check permissions
    chks t1, t4, IntGateCheck

    mov t1, t1, t4, dataSize=8

    # Check that it's the right type
    srli t4, t1, 40, dataSize=8
    andi t4, t4, 0xe, dataSize=8
    xori t4, t4, 0xe, flags=(EZF,), dataSize=8
    fault "new GeneralProtection(0)", flags=(nCEZF,)


    #
    # Get the target CS descriptor using the selector in the gate
    # descriptor.
    #
    srli t4, t1, 16, dataSize=8
    andi t5, t4, 0xF8, dataSize=8
    andi t0, t4, 0x4, flags=(EZF,), dataSize=2
    br rom_local_label("globalDescriptor"), flags=(CEZF,)
    ld t3, tsl, [1, t0, t5], dataSize=8, addressSize=8
    br rom_local_label("processDescriptor")
globalDescriptor:
    ld t3, tsg, [1, t0, t5], dataSize=8, addressSize=8
processDescriptor:
    chks t4, t3, IntCSCheck, dataSize=8
    wrdl hs, t3, t4, dataSize=8

    # Check that the target offset is in canonical form
    wrdh t4, t1, t2, dataSize=8
    srli t4, t4, 47, dataSize=8
    addi t4, t4, 1, dataSize=8
    srli t4, t4, 1, dataSize=8
    or t4, t4, t4, flags=(EZF,), dataSize=2
    fault "new GeneralProtection(0)", flags=(nCEZF,)


    #
    # Figure out where the stack should be
    #

    # Record what we might set the stack selector to.
    rdsel t6, ss
    wrsel hs, t6

    # Check if we're changing privelege level. At this point we can assume
    # we're going to a DPL that's less than or equal to the CPL.
    rdattr t4, hs, dataSize=8
    srli t4, t4, 3, dataSize=8
    andi t4, t4, 3, dataSize=8
    rdattr t5, cs, dataSize=8
    srli t5, t5, 3, dataSize=8
    sub t5, t5, t4, dataSize=8
    andi t0, t5, 0x3, flags=(EZF,), dataSize=8
    # We're going to change priviledge, so zero out the stack selector. We
    # need to let the IST have priority so we don't branch yet.
    limm t4, 0
    wrsel hs, t4, flags=(nCEZF,)

    # Check the IST field of the gate descriptor
    srli t4, t1, 32, dataSize=8
    andi t4, t4, 0x7, dataSize=8
    subi t0, t4, 1, flags=(ECF,), dataSize=8
    br rom_local_label("istStackSwitch"), flags=(nCECF,)
    br rom_local_label("cplStackSwitch"), flags=(nCEZF,)

    # If we're here, it's because the stack isn't being switched.
    # Set t6 to the new rsp.
    subi t6, rsp, 40, dataSize=8

    # Align the stack
    andi t6, t6, 0xF0, dataSize=1

    # Check that we can access everything we need to on the stack
    ldst t0, hs, [1, t0, t6], dataSize=8, addressSize=8
    ldst t0, hs, [1, t0, t6], 32, dataSize=8, addressSize=8
    br rom_local_label("stackSwitched")

istStackSwitch:
    panic "IST based stack switching isn't implemented"
    br rom_local_label("stackSwitched")

cplStackSwitch:
    panic "CPL change initiated stack switching isn't implemented"

stackSwitched:


    ##
    ## Point of no return.
    ## We're now going to irrevocably modify visible state.
    ## Anything bad that's going to happen should have happened by now.
    ##


    #
    # Build up the interrupt stack frame
    #

    # Write out the contents of memory
    st t7, hs, [1, t0, t6], dataSize=8
    limm t5, 0, dataSize=8
    rdsel t5, cs, dataSize=2
    st t5, hs, [1, t0, t6], 8, dataSize=8
    rflags t4, dataSize=8
    st t4, hs, [1, t0, t6], 16, dataSize=8
    st rsp, hs, [1, t0, t6], 24, dataSize=8
    rdsel t5, ss, dataSize=2
    st t5, hs, [1, t0, t6], 32, dataSize=8

    # Set the stack segment
    mov rsp, rsp, t6, dataSize=8
    rdsel t7, hs, dataSize=2
    wrsel ss, t7, dataSize=2

    #
    # Set up the target code segment
    #
    srli t5, t1, 16, dataSize=8
    andi t5, t5, 0xFF, dataSize=8
    wrdl cs, t3, t5, dataSize=8
    wrsel cs, t5, dataSize=2
    wrdh t7, t1, t2, dataSize=8
    wrip t0, t7, dataSize=8

    #
    # Adjust rflags which is still in t4 from above
    #

    # Set IF to the lowest bit of the original gate type.
    # The type field of the original gate starts at bit 40.

    # Set the TF, NT, and RF bits. We'll flip them at the end.
    limm t6, (1 << 8) | (1 << 14) | (1 << 16)
    or t4, t4, t6
    srli t5, t1, 40, dataSize=8
    srli t7, t4, 9, dataSize=8
    xor t5, t7, t5, dataSize=8
    andi t5, t5, 1, dataSize=8
    slli t5, t5, 9, dataSize=8
    or t6, t5, t6, dataSize=8

    # Put the results into rflags
    wrflags t6, t4

    eret
};

def rom
{
    # This vectors the CPU into an interrupt handler in legacy mode.
    extern legacyModeInterrupt:
    panic "Legacy mode interrupts not implemented (in microcode)"
    eret
};
'''