Assorted trap improvements and add Smdbltrp extension

1 files changed, 60 insertions, 19 deletions

diff --git a/rvcontroller.lua b/rvcontroller.lua
index 1acb1f1..37b09f5 100644
--- a/rvcontroller.lua
+++ b/rvcontroller.lua
@@ -50,6 +50,8 @@ Intended to be compliant with the following specifications:
 * Zbkx: Extension for Crossbar permutations, Version 1.0.0
 * Xh3bextm: Hazard3 bit extract multiple
 	- Note: Defined in the Hazard3 reference manual, available at https://github.com/Wren6991/Hazard3/releases/download/v1.1/hazard3.pdf
+* Machine-Level ISA, Version 1.13
+* "Smdbltrp" Double Trap Extension, Version 1.0
 
 See https://docs.riscv.org/reference/isa/unpriv/unpriv-index.html for full specifications.
 
@@ -338,7 +340,7 @@ local function setreg(reg,val)
 end
 
 local function readram(address,bytes,instfetch)
-	local bigendian = mem.bigendian and not instfetch --Instruction fetches must always be little-endian
+	local bigendian = mem.mbe and not instfetch --Instruction fetches must always be little-endian
 	if address > RAM_SIZE-1 and not (address >= mem.csr[0x801] and address <= mem.csr[0x801] + 1) then
 		fault = instfetch and 1 or 5
 		return instfetch and 0x13 or 0 --0x13 = addi x0,x0,0
@@ -401,7 +403,7 @@ local function writeram(address,data,bytes,fake)
 		local thisbyte = data % (2^((i+1)*8)) / 2^(i*8)
 		thisbyte = math.floor(thisbyte) % 2^32
 		local offsetaddr
-		if mem.bigendian then
+		if mem.mbe then
 			offsetaddr = address+bytes-1-i
 		else
 			offsetaddr = address+i
@@ -492,7 +494,28 @@ local function stdout(text)
 end
 
 local function readcsr(address)
-	if not mem.csr[address] then
+	if address == 0x341 then --mepc
+		local ret = mem.csr[0x341]
+		--mepc[0] must be 0
+		if ret%2 == 1 then ret = ret-1 end
+		--mepc[1] must be 0 if IALIGN=32
+		if not mem.isa.c and ret%4 >= 2 then
+			ret = ret - 2
+		end
+		return ret
+	elseif address == 0x300 then --mstatus
+		local bits = {}
+		bits[3] = mem.mie
+		bits[7] = mem.mpie
+		bits[11] = mem.mpp%2 == 1
+		bits[12] = mem.mpp >= 2
+		return implodebits(bits,32)
+	elseif address == 0x310 then --mstatush
+		local bits = {}
+		bits[5] = mem.mbe
+		bits[10] = mem.mdt
+		return implodebits(bits,32)
+	elseif not mem.csr[address] then
 		digiline_send("monitordisp",string.format("Attempted read\nfrom unknown\nCSR 0x%03X\nPC: %08X",address,mem.registers.pc))
 		fault = 2
 		return 0
@@ -505,16 +528,24 @@ local function writecsr(address,data)
 		--jvt
 		data = math.floor(data/2^6)*2^6 --WARL, and mode is required to be 0
 	elseif address == 0xc00 or address == 0xc01 or address == 0xc02 or address == 0xc80 or address == 0xc81 or address == 0xc82 then
-		--One of the read-only CSRs from Zicntr, just ignore the write
+		--One of the read-only CSRs from Zicntr
+		fault = 2
 		return
-	elseif address == 0xf11 or address == 0xf12 or address == 0xf13 or address == 0xf14 or address == 0xf15 or address == 0x300 then
-		--Read-only machine information register, ignore write
+	elseif address == 0xf11 or address == 0xf12 or address == 0xf13 or address == 0xf14 or address == 0xf15 then
+		--Read-only machine information register
+		fault = 2
+		return
+	elseif address == 0x300 then
+		--mstatus
+		local bits = explodebits(data,32)
+		mem.mie = bits[3] and not mem.mdt
+		mem.mpie = bits[7]
 		return
 	elseif address == 0x310 then
 		--mstatush
 		local bits = explodebits(data,32)
-		mem.bigendian = bits[5]
-		mem.csr[0x310] = mem.bigendian and 0x20 or 0
+		mem.mbe = bits[5]
+		mem.mdt = bits[10]
 		return
 	elseif address == 0x301 then
 		--misa
@@ -556,7 +587,10 @@ local function trap(reason)
 	writecsr(0x342,reason) --mcause
 	writecsr(0x341,mem.registers.pc) --mepc
 	writecsr(0x343,0) --mtval
-	if mem.trapbase then
+	mem.mpie = mem.mie
+	mem.mie = false
+	if not mem.mdt then
+		mem.mdt = 1
 		if mem.trapmode == 1 then
 			--vectored mode
 			local int = reason >= 0x8000000
@@ -569,7 +603,7 @@ local function trap(reason)
 			return true,false
 		end
 	else
-		digiline_send("monitordisp","Unhandled trap!")
+		digiline_send("monitordisp","Unexpected trap!")
 		digiline_send("monitordisp",traptypes[reason] or "Unknown reason")
 		digiline_send("monitordisp",string.format("PC: %08X",mem.registers.pc))
 		digiline_send("monitordisp","System halted")
@@ -859,8 +893,8 @@ local operations = {
 		if rd == 0 or rd == 31 then return end
 		if imm >= 2^11 then imm = imm - 2^12 end
 		local address = getreg(rs1)+imm
-		setreg(rd,readram(address+(mem.bigendian and 4 or 0),4))
-		setreg(rd+1,readram(address+(mem.bigendian and 0 or 4),4))
+		setreg(rd,readram(address+(mem.mbe and 4 or 0),4))
+		setreg(rd+1,readram(address+(mem.mbe and 0 or 4),4))
 	end,
 	lhu = function(rd,rs1,imm)
 		if imm >= 2^11 then imm = imm - 2^12 end
@@ -888,8 +922,8 @@ local operations = {
 		if rs2 == 31 then return end
 		if imm >= 2^11 then imm = imm - 2^12 end
 		local address = getreg(rs1)+imm
-		writeram(address+(mem.bigendian and 4 or 0),getreg(rs2),4)
-		writeram(address+(mem.bigendian and 0 or 4),getreg(rs2+1),4)
+		writeram(address+(mem.mbe and 4 or 0),getreg(rs2),4)
+		writeram(address+(mem.mbe and 0 or 4),getreg(rs2+1),4)
 	end,
 	ecall = function()
 		local func = mem.isa.i and getreg(17) or getreg(15)
@@ -1787,6 +1821,10 @@ local operations = {
 	end,
 	mret = function()
 		mem.registers.pc = readcsr(0x341)
+		mem.mie = mem.mpie
+		mem.mpie = true
+		mem.mpp = 3
+		mem.mdt = false
 		return true
 	end,
 }
@@ -2714,7 +2752,6 @@ if event.type == "program" or event.iid == "reset" then
 			[0x300] = 0, --mstatus
 			[0x301] = 0x40001107, --misa (RV32IMACB)
 			[0x305] = 0, --mtvec
-			[0x310] = 0, --mstatush
 			[0x340] = 0, --mscratch
 			[0x341] = 0, --mepc
 			[0x342] = 0, --mcause
@@ -2737,7 +2774,7 @@ if event.type == "program" or event.iid == "reset" then
 	mem.breakpoint = -1
 	mem.hexloading = false
 	mem.reservationset = nil
-	mem.bigendian = false
+	mem.mbe = false
 	mem.isa = {
 		a = true,
 		b = true,
@@ -2748,8 +2785,12 @@ if event.type == "program" or event.iid == "reset" then
 	mem.meseconsdir = {}
 	mem.meseconsdata = {}
 	port = {}
-	mem.trapbase = nil
-	mem.trapmode = nil
+	mem.trapbase = 0
+	mem.trapmode = 0
+	mem.mie = false
+	mem.mpie = true
+	mem.mpp = 3
+	mem.mdt = true
 elseif event.type == "on" or event.type == "off" then
 	local pname = string.lower(event.pin.name)
 	local pstate = pin[pname]
@@ -2923,7 +2964,7 @@ elseif event.channel == "monitorkb" then
 		digiline_send("monitordisp",string.format("%03X: %08X",address,readcsr(address)))
 	elseif argv[1] == "endian" then
 		if argc == 1 then
-			digiline_send("monitordisp",mem.bigendian and "Big-endian" or "Little-endian")
+			digiline_send("monitordisp",mem.mbe and "Big-endian" or "Little-endian")
 		elseif argv[2] == "b" or argv[2] == "big" then
 			local bits = explodebits(readcsr(0x310),32) --mstatush
 			bits[5] = true --MBE