mirror of
https://github.com/danbulant/Cosmos
synced 2026-05-20 21:08:51 +00:00
106 lines
2.9 KiB
Text
106 lines
2.9 KiB
Text
Group DebugStub
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# Input: AL
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# Output: None
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# Modifies: EDX, ESI
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procedure WriteALToComPort {
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+EAX
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ESI = ESP
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Call .WriteByteToComPort
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# Is a local var, cant use Return(4). X# issues the return.
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# This also allows the function to preserve EAX.
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-EAX
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}
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# SERIAL DOCS
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#
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# All information relating to our serial usage should be documented in this comment.
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#
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# We do not use IRQs for debugstub serial. This is becuase DebugStub (DS)
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# MUST be:
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# - As simple as possible
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# - Interact as minimal as possible wtih normal Cosmos code because
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# the debugstub must *always* work even if the normal code is fubarred
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#
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# The serial port that is used for DS should be 'hidden' from Cosmos main
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# so that Cosmos main pretends it does not exist.
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#
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# IRQs would create a clash/mix of code.
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# This does make the serial code in DebugStub inefficient, but its well worth
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# the benefits received by following these rules.
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#
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# Baud rate is set to 115200. Likely our code could not exceed this rate
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# anyways the way it is written and there are compatibility issues on some
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# hardware above this rate.
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#
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# We assume a minimum level of a 16550A, which should be no problem on any
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# common hardware today. VMWare emulates the 16550A
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#
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# We do not handle flow control for outbound data (DS --> DC).
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# The DebugConnector (DC, the code in the Visual Studio side) however is threaded
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# and easily should be able to receive data faster than we can send it.
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# Most things are transactional with data being sent only when asked for, but
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# with tracing we do send a data directly.
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#
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# Currently there is no inbound flow control either (DC --> DS)
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# For now we assume all commands in bound are 16 bytes or less to ensure
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# that they fit in the FIFO. Commands in DS must wait for a command ID ACK
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# before sending another command.
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# See notes in ProcessCommand.
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#
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# http:#www.nondot.org/sabre/os/files/Communication/ser_port.txt
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# Todo Auto params
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# Todo ebp frame ptr auto etc
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# Input - Address on stack as x32
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procedure InitSerial2 {
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# Disable interrupts
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DX = ESP[4]
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DX + 1
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AL = 0
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Port[DX] = AL
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# Enable DLAB (set baud rate divisor)
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DX = ESP[4]
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DX + 3
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AL = $80
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Port[DX] = AL
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# 0x01 - 0x00 - 115200
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# 0x02 - 0x00 - 57600
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# 0x03 - 0x00 - 38400
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#
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# Set divisor (lo byte)
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DX = ESP[4]
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AL = $01
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Port[DX] = AL
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# hi byte
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DX = ESP[4]
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DX + 1
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AL = $00
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Port[DX] = AL
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# 8N1
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DX = ESP[4]
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DX + 3
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AL = $03
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Port[DX] = AL
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# Enable FIFO, clear them
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# Set 14-byte threshold for IRQ.
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# We dont use IRQ, but you cant set it to 0
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# either. IRQ is enabled/diabled separately
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DX = ESP[4]
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DX + 2
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AL = $C7
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Port[DX] = AL
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# 0x20 AFE Automatic Flow control Enable - 16550 (VMWare uses 16550A) is most common and does not support it
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# 0x02 RTS
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# 0x01 DTR
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# Send 0x03 if no AFE
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DX = ESP[4]
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DX + 4
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AL = $03
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Port[DX] = AL
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}
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