xref: /gem5/src/arch/x86/isa/insts/general_purpose/control_transfer/xreturn.py

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# Authors: Gabe Black

microcode = '''
def macroop RET_NEAR
{
    # Make the default data size of rets 64 bits in 64 bit mode
    .adjust_env oszIn64Override

    ld t1, ss, [1, t0, rsp]
    # Check address of return
    addi rsp, rsp, dsz
    wripi t1, 0
};

def macroop RET_NEAR_I
{
    # Make the default data size of rets 64 bits in 64 bit mode
    .adjust_env oszIn64Override

    limm t2, imm
    ld t1, ss, [1, t0, rsp]
    # Check address of return
    addi rsp, rsp, dsz
    add rsp, rsp, t2
    wripi t1, 0
};

def macroop RET_FAR {
    .adjust_env oszIn64Override

    # Get the return RIP
    ld t1, ss, [1, t0, rsp]

    # Get the return CS
    ld t2, ss, [1, t0, rsp], ssz

    # Get the rpl
    andi t3, t2, 0x3

    # Get the cpl

    # Here we'd check if we're changing priviledge levels. We'll just hope
    # that doesn't happen yet.

    # Do stuff if they're equal
    andi t0, t2, 0xFC, flags=(EZF,), dataSize=2
    br label("processDescriptor"), flags=(CEZF,)
    andi t3, t2, 0xF8, dataSize=8
    andi t0, t2, 0x4, flags=(EZF,), dataSize=2
    br label("globalDescriptor"), flags=(CEZF,)
    ld t3, tsl, [1, t0, t3], dataSize=8
    br label("processDescriptor")
globalDescriptor:
    ld t3, tsg, [1, t0, t3], dataSize=8
processDescriptor:
    chks t2, t3, IretCheck, dataSize=8
    # There should be validity checks on the RIP checks here, but I'll do
    # that later.
    wrdl cs, t3, t2
    wrsel cs, t2
    wrip t0, t1
    br label("end")

    # Do other stuff if they're not.
end:
    fault "NoFault"
};
'''