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a-machine/amach.awk
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#!/usr/bin/env awk -f
# A-Machine: an experimental RISC-V (RV32IMAC) emulator in POSIX AWK
# with a very small subset of supported ECALLs
# Accepts a headerless binary previously converted to .dec format
# e.g. with POSIX od: od -An -v -tu1 program.bin > program.dec
# Usage: awk -f amach.awk [-v LVA=...] -- prog.dec
# Or run a .bin directly with:
# od -An -v -tu1 program.bin | awk -f amach.awk [-v LVA=...]
# Created by Luxferre in 2026, released into the public domain
# fatal error reporting function
function trapout(msg, fd) {
for(fd in FD_PATH) {
if(FD_DIRTY[fd]) {
write_fd_to_file(fd)
}
}
cmd = "cat 1>&2"
printf("Fatal: %s\n", msg) | cmd
close(cmd)
exit(1)
}
# helper functions
function uint32(val) {
val = int(val) % 4294967296
return (val < 0) ? (val + 4294967296) : val
}
function setreg(idx, val) {
if(idx > 0) {
val = uint32(val)
REG[idx] = (val >= 2147483648) ? (val - 4294967296) : val
}
}
function getreg(idx) {return (idx == 0) ? 0 : int(REG[idx])}
function imm_sign_ex(val) {val = int(val); return (val >= 2048) ? (val - 4096) : val}
function imm_sign_ex_b(val) {val = int(val); return (val >= 4096) ? (val - 8192) : val}
function floor(x, i) {
i = int(x)
return (x >= 0 || x == i) ? i : (i - 1)
}
function ord(c, b) {
if(!TGL_ORD["#"]) for(b=0;b<256;b++) TGL_ORD[sprintf("%c", b)] = b
return int(TGL_ORD[c])
}
function bw_op(a, b, op, v, r) {
v = 1; r = 0; a = uint32(a); b = uint32(b)
while(a > 0 || b > 0) {
if(op == "&" && (a%2) == 1 && (b%2) == 1) r += v
else if(op == "|" && ((a%2) == 1 || (b%2) == 1)) r += v
else if(op == "^" && (a%2) != (b%2)) r += v
a = int(a/2); b = int(b/2); v *= 2
}
return int(r)
}
function bw_and(a, b) {return bw_op(a, b, "&")}
function bw_or(a, b) {return bw_op(a, b, "|")}
function bw_xor(a, b) {return bw_op(a, b, "^")}
function read_mem(addr, bytes, signed, i, val, max_val) {
addr = uint32(addr)
val = 0
for(i=0; i<bytes; i++) val += MEM[(addr+i)%4294967296] * (256^i)
if(signed) {
max_val = 256^bytes
if(val >= max_val/2) val -= max_val
}
return val
}
function write_mem(addr, val, bytes, i) {
addr = uint32(addr)
val = uint32(val)
for(i=0; i<bytes; i++) MEM[(addr+i)%4294967296] = int(val / (256^i)) % 256
}
function read_word(addr) {return read_mem(addr, 4, 1)}
function write_word(addr, val) {write_mem(addr, val, 4)}
# Escapes single quotes for shell command safety
function qquote(str) {
gsub(/'/, "'\\''", str)
return "'" str "'"
}
# Converts hex string to decimal
function hex_to_dec(hex, dec, i, len, c, val) {
dec = 0
len = length(hex)
for (i = 1; i <= len; i++) {
c = tolower(substr(hex, i, 1))
if (c ~ /[0-9]/) val = int(c)
else if (c == "a") val = 10
else if (c == "b") val = 11
else if (c == "c") val = 12
else if (c == "d") val = 13
else if (c == "e") val = 14
else if (c == "f") val = 15
else continue
dec = dec * 16 + val
}
return dec
}
# Reads a null-terminated string from memory
function read_str(addr, c, s) {
s = ""
addr = uint32(addr)
while ((c = MEM[addr++]) != 0) {
s = s sprintf("%c", c)
}
return s
}
# Checks if path exists using POSIX test -e or test -L
function path_exists(path) {
return (system("test -e " qquote(path)) == 0 || system("test -L " qquote(path)) == 0)
}
# Checks if path is a directory using POSIX test -d
function is_dir(path) {
return (system("test -d " qquote(path)) == 0)
}
# Resolves relative path against dfd directory
function resolve_path(dfd, pathname, path) {
if (substr(pathname, 1, 1) == "/") {
return pathname
}
if (dfd == -100) { # AT_FDCWD
return pathname
}
if (dfd in FD_PATH) {
return FD_PATH[dfd] "/" pathname
}
return pathname
}
# Populate timespec structure
# TV_SEC: 64-bit for clock_gettime64, 32-bit for clock_gettime
function get_system_time(time_arr, cmd, line) {
cmd = "date +%s%N"
if ((cmd | getline line) > 0) {
if (length(line) > 9 && line ~ /^[0-9]+$/) {
time_arr["sec"] = int(substr(line, 1, length(line) - 9))
time_arr["nsec"] = int(substr(line, length(line) - 8))
close(cmd)
return
}
}
close(cmd)
# Fallback if %N is not supported
cmd = "date +%s"
if ((cmd | getline line) > 0) {
time_arr["sec"] = int(line)
} else {
time_arr["sec"] = 0
}
close(cmd)
if (time_arr["sec"] == LAST_SEC) {
VIRT_NSEC += 500000
if (VIRT_NSEC >= 1000000000) {
VIRT_NSEC = 999999999
}
} else {
LAST_SEC = time_arr["sec"]
VIRT_NSEC = 0
}
time_arr["nsec"] = VIRT_NSEC
}
# Fills stat structure in VM memory
function fill_stat_struct(path, addr, follow, cmd, line, parts, opt, mode_hex, mode_dec, size, atime, mtime, ctime, i) {
opt = follow ? "-L " : ""
cmd = "stat " opt "-c \"%f %s %X %Y %Z\" " qquote(path)
if ((cmd | getline line) > 0) {
split(line, parts)
mode_hex = parts[1]
mode_dec = hex_to_dec(mode_hex)
size = int(parts[2])
atime = int(parts[3])
mtime = int(parts[4])
ctime = int(parts[5])
close(cmd)
for (i = 0; i < 104; i++) {
MEM[addr + i] = 0
}
write_mem(addr + 0, 1, 8)
write_mem(addr + 8, 1, 8)
write_mem(addr + 16, mode_dec, 4)
write_mem(addr + 20, 1, 4)
write_mem(addr + 24, 1000, 4)
write_mem(addr + 28, 1000, 4)
write_mem(addr + 32, 0, 8)
write_mem(addr + 48, size, 8)
write_mem(addr + 56, 4096, 4)
write_mem(addr + 64, int((size + 511) / 512), 8)
write_mem(addr + 72, atime, 4)
write_mem(addr + 80, mtime, 4)
write_mem(addr + 88, ctime, 4)
return 0
} else {
close(cmd)
return -2
}
}
# Writes file descriptor cached data back to file
function write_fd_to_file(fd, path, chunk, i, size) {
path = FD_PATH[fd]
size = FD_SIZE[fd]
printf("") > path
close(path)
chunk = ""
for (i = 0; i < size; i++) {
chunk = chunk sprintf("%c", FD_DATA[fd, i])
if (length(chunk) >= 1024) {
printf("%s", chunk) >> path
chunk = ""
}
}
if (length(chunk) > 0) {
printf("%s", chunk) >> path
}
close(path)
}
function amach_exit(code, fd) {
for (fd in FD_PATH) {
if (FD_DIRTY[fd]) {
write_fd_to_file(fd)
}
}
exit(code)
}
# syscall emulation
function handle_ecall(callnum, a0, a1, a2, a3, a4, a5, i, l, buf, path, pathname, flags, fd, count, now_time, dtype, full_path, reclen, bytes_written, idx, count_limit, buf_addr, name, status, follow, oldpath, newpath, access_mode, is_read, is_write, do_trunc, cmd, line, arr, size, buflen) {
if (callnum == 34) { # sys_mkdirat
pathname = read_str(a1)
path = resolve_path(a0, pathname)
if (path_exists(path)) {
setreg(10, -17) # -EEXIST
} else {
status = system("mkdir " qquote(path))
setreg(10, (status == 0) ? 0 : -2)
}
} else if (callnum == 35) { # sys_unlinkat
pathname = read_str(a1)
path = resolve_path(a0, pathname)
if (!path_exists(path)) {
setreg(10, -2) # -ENOENT
} else {
if (bw_and(a2, 512)) { # AT_REMOVEDIR (0x200)
status = system("rmdir " qquote(path))
} else {
status = system("rm " qquote(path))
}
setreg(10, (status == 0) ? 0 : -1)
}
} else if (callnum == 38 || callnum == 276) { # sys_renameat / sys_renameat2
oldpath = resolve_path(a0, read_str(a1))
newpath = resolve_path(a2, read_str(a3))
status = system("mv " qquote(oldpath) " " qquote(newpath))
setreg(10, (status == 0) ? 0 : -1)
} else if (callnum == 56) { # sys_openat
pathname = read_str(a1)
path = resolve_path(a0, pathname)
flags = a2
if (bw_and(flags, 64)) { # O_CREAT (0x40)
if (bw_and(flags, 128) && path_exists(path)) { # O_EXCL (0x80)
setreg(10, -17) # -EEXIST
return
}
if (!path_exists(path)) {
printf("") > path
close(path)
}
} else {
if (!path_exists(path)) {
setreg(10, -2) # -ENOENT
return
}
}
fd = NEXT_FD++
FD_PATH[fd] = path
FD_FLAGS[fd] = flags
FD_OFFSET[fd] = 0
FD_SIZE[fd] = 0
FD_DIRTY[fd] = 0
if (is_dir(path)) {
cmd = "ls -a1 " qquote(path)
count = 0
while ((cmd | getline line) > 0) {
if (line != "") {
FD_DIRENTS[fd, count++] = line
}
}
close(cmd)
FD_DIRENT_COUNT[fd] = count
} else {
access_mode = bw_and(flags, 3)
is_read = (access_mode == 0 || access_mode == 2)
is_write = (access_mode == 1 || access_mode == 2)
do_trunc = (is_write && bw_and(flags, 512)) # O_TRUNC (0x200)
if (is_read && !do_trunc) {
cmd = "od -An -v -tu1 " qquote(path)
size = 0
while ((cmd | getline line) > 0) {
split(line, arr)
for (i = 1; i in arr; i++) {
FD_DATA[fd, size++] = arr[i]
}
}
close(cmd)
FD_SIZE[fd] = size
} else if (do_trunc) {
printf("") > path
close(path)
}
}
setreg(10, fd)
} else if (callnum == 57) { # sys_close
fd = a0
if (fd >= 3 && (fd in FD_PATH)) {
if (FD_DIRTY[fd]) {
write_fd_to_file(fd)
}
delete FD_PATH[fd]
delete FD_FLAGS[fd]
delete FD_OFFSET[fd]
delete FD_SIZE[fd]
delete FD_DIRTY[fd]
if (fd in FD_DIRENT_COUNT) {
for (i = 0; i < FD_DIRENT_COUNT[fd]; i++) {
delete FD_DIRENTS[fd, i]
}
delete FD_DIRENT_COUNT[fd]
} else {
for (i = 0; i < FD_SIZE[fd]; i++) {
delete FD_DATA[fd, i]
}
}
setreg(10, 0)
} else {
setreg(10, -9) # -EBADF
}
} else if (callnum == 61) { # sys_getdents64
fd = a0
if (!(fd in FD_DIRENT_COUNT)) {
setreg(10, -9) # -EBADF
} else {
bytes_written = 0
idx = FD_OFFSET[fd]
count_limit = a2
buf_addr = a1
while (idx < FD_DIRENT_COUNT[fd]) {
name = FD_DIRENTS[fd, idx]
reclen = int((20 + length(name) + 7) / 8) * 8
if (bytes_written + reclen > count_limit) {
if (bytes_written == 0) {
setreg(10, -22) # -EINVAL
return
}
break
}
write_mem(buf_addr + bytes_written, 1, 8)
write_mem(buf_addr + bytes_written + 8, idx + 1, 8)
write_mem(buf_addr + bytes_written + 16, reclen, 2)
full_path = FD_PATH[fd] "/" name
dtype = is_dir(full_path) ? 4 : 8
write_mem(buf_addr + bytes_written + 18, dtype, 1)
for (i = 0; i < length(name); i++) {
MEM[buf_addr + bytes_written + 19 + i] = ord(substr(name, i + 1, 1))
}
MEM[buf_addr + bytes_written + 19 + length(name)] = 0
for (i = 19 + length(name) + 1; i < reclen; i++) {
MEM[buf_addr + bytes_written + i] = 0
}
bytes_written += reclen
idx++
}
FD_OFFSET[fd] = idx
setreg(10, bytes_written)
}
} else if (callnum == 62) { # sys_lseek
fd = a0
if (fd >= 3 && (fd in FD_PATH) && !(fd in FD_DIRENT_COUNT)) {
idx = FD_OFFSET[fd]
size = FD_SIZE[fd]
if (a2 == 0) idx = a1 # SEEK_SET
else if (a2 == 1) idx = idx + a1 # SEEK_CUR
else if (a2 == 2) idx = size + a1 # SEEK_END
else {
setreg(10, -22) # -EINVAL
return
}
if (idx < 0) {
setreg(10, -22) # -EINVAL
} else {
FD_OFFSET[fd] = idx
setreg(10, idx)
}
} else {
setreg(10, -9) # -EBADF
}
} else if (callnum == 63) { # sys_read
fd = a0
if (fd == 0) {
getline buf < "/dev/tty"
l = length(buf); if (l > a2) l = a2
for (i = 0; i < l; i++) MEM[uint32(a1 + i)] = ord(substr(buf, i + 1, 1))
setreg(10, l)
} else if (fd >= 3 && (fd in FD_PATH) && !(fd in FD_DIRENT_COUNT)) {
idx = FD_OFFSET[fd]
size = FD_SIZE[fd]
count = a2
if (idx >= size) {
setreg(10, 0)
} else {
if (idx + count > size) count = size - idx
for (i = 0; i < count; i++) {
MEM[uint32(a1 + i)] = FD_DATA[fd, idx + i]
}
FD_OFFSET[fd] = idx + count
setreg(10, count)
}
} else {
setreg(10, -9) # -EBADF
}
} else if (callnum == 64) { # sys_write
fd = a0
if (fd == 1 || fd == 2) {
for (i = 0; i < a2; i++) printf("%c", MEM[uint32(a1 + i)])
setreg(10, a2)
} else if (fd >= 3 && (fd in FD_PATH) && !(fd in FD_DIRENT_COUNT)) {
idx = FD_OFFSET[fd]
count = a2
if (bw_and(FD_FLAGS[fd], 1024)) { # O_APPEND (0x400)
idx = FD_SIZE[fd]
}
for (i = 0; i < count; i++) {
FD_DATA[fd, idx + i] = MEM[uint32(a1 + i)]
}
FD_OFFSET[fd] = idx + count
if (FD_OFFSET[fd] > FD_SIZE[fd]) {
FD_SIZE[fd] = FD_OFFSET[fd]
}
FD_DIRTY[fd] = 1
setreg(10, count)
} else {
setreg(10, -9) # -EBADF
}
} else if (callnum == 78) { # sys_readlinkat
path = resolve_path(a0, read_str(a1))
cmd = "readlink " qquote(path)
if ((cmd | getline line) > 0) {
close(cmd)
l = length(line)
if (l > a3) l = a3
for (i = 0; i < l; i++) {
MEM[uint32(a2 + i)] = ord(substr(line, i + 1, 1))
}
setreg(10, l)
} else {
close(cmd)
setreg(10, -22) # -EINVAL
}
} else if (callnum == 79) { # sys_newfstatat
pathname = read_str(a1)
flags = a3
if (pathname == "" && bw_and(flags, 4096)) { # AT_EMPTY_PATH
if (a0 == -100) path = "."
else if (a0 in FD_PATH) path = FD_PATH[a0]
else {
setreg(10, -9) # -EBADF
return
}
} else {
path = resolve_path(a0, pathname)
}
follow = (bw_and(flags, 256) == 0) # follow link if AT_SYMLINK_NOFOLLOW (0x100) is NOT set
status = fill_stat_struct(path, a2, follow)
setreg(10, status)
} else if (callnum == 80) { # sys_fstat
fd = a0
if (fd == 0) path = "/dev/stdin"
else if (fd == 1) path = "/dev/stdout"
else if (fd == 2) path = "/dev/stderr"
else if (fd >= 3 && (fd in FD_PATH)) path = FD_PATH[fd]
else {
setreg(10, -9) # -EBADF
return
}
status = fill_stat_struct(path, a1, 1)
setreg(10, status)
} else if (callnum == 93 || callnum == 94) { # sys_exit / sys_exit_group
amach_exit(a0)
} else if (callnum == 113 || callnum == 403) { # sys_clock_gettime / sys_clock_gettime64
get_system_time(now_time)
if (callnum == 113) {
write_mem(a1, now_time["sec"], 4)
write_mem(a1 + 4, now_time["nsec"], 4)
} else {
write_mem(a1, now_time["sec"], 8)
write_mem(a1 + 8, now_time["nsec"], 4)
}
setreg(10, 0)
} else if (callnum == 169) { # sys_gettimeofday
get_system_time(now_time)
write_mem(a0, now_time["sec"], 4)
write_mem(a0 + 4, int(now_time["nsec"] / 1000), 4)
setreg(10, 0)
} else if (callnum == 278) { # sys_getrandom
buf_addr = a0
buflen = a1
for (i = 0; i < buflen; i++) {
MEM[uint32(buf_addr + i)] = int(rand() * 256)
}
setreg(10, buflen)
} else {
trapout(sprintf("Unimplemented environment call %d at 0x%X", callnum, pc - 4))
}
}
# instruction type executors
function amach_reg_arith(f3, f7, rd, rs1, rs2, r1, r2, ur1, ur2, shamt) {
r1 = getreg(rs1); r2 = getreg(rs2)
ur1 = uint32(r1); ur2 = uint32(r2)
shamt = ur2 % 32
if(f3 == 0 && f7 == 0) setreg(rd, r1 + r2)
else if(f3 == 0 && f7 == 32) setreg(rd, r1 - r2)
else if(f3 == 4 && f7 == 0) setreg(rd, bw_xor(r1, r2))
else if(f3 == 6 && f7 == 0) setreg(rd, bw_or(r1, r2))
else if(f3 == 7 && f7 == 0) setreg(rd, bw_and(r1, r2))
else if(f3 == 1 && f7 == 0) setreg(rd, (r1 * (2^shamt)) % 4294967296)
else if(f3 == 5 && f7 == 0) setreg(rd, int(ur1 / (2^shamt)))
else if(f3 == 5 && f7 == 32) setreg(rd, floor(r1 / (2^shamt)))
else if(f3 == 2 && f7 == 0) setreg(rd, (r1 < r2) ? 1 : 0)
else if(f3 == 3 && f7 == 0) setreg(rd, (ur1 < ur2) ? 1 : 0)
else if(f3 == 0 && f7 == 1) setreg(rd, (r1 * r2) % 4294967296)
else if(f3 == 1 && f7 == 1) setreg(rd, floor((r1 * r2) / 4294967296))
else if(f3 == 2 && f7 == 1) setreg(rd, floor((r1 * ur2) / 4294967296))
else if(f3 == 3 && f7 == 1) setreg(rd, floor((ur1 * ur2) / 4294967296))
else if(f3 == 4 && f7 == 1) setreg(rd, (r2 == 0) ? -1 : int(r1 / r2))
else if(f3 == 5 && f7 == 1) setreg(rd, (r2 == 0) ? 4294967295 : int(ur1 / ur2))
else if(f3 == 6 && f7 == 1) setreg(rd, (r2 == 0) ? r1 : (r1 % r2))
else if(f3 == 7 && f7 == 1) setreg(rd, (r2 == 0) ? r1 : (ur1 % ur2))
else trapout(sprintf("Illegal instruction at 0x%X", pc-4))
}
function amach_store(f3, rs1, rs2, immval, r1, r2) {
r1 = getreg(rs1); r2 = getreg(rs2)
if(f3 >= 0 && f3 <= 2) write_mem(r1 + immval, r2, 2^f3)
else trapout(sprintf("Illegal instruction at 0x%X", pc-4))
}
function amach_branch(f3, rs1, rs2, immval, r1, r2, ur1, ur2, taken) {
r1 = getreg(rs1); r2 = getreg(rs2)
ur1 = uint32(r1); ur2 = uint32(r2)
taken = 0
if(f3 == 0) taken = (r1 == r2)
else if(f3 == 1) taken = (r1 != r2)
else if(f3 == 4) taken = (r1 < r2)
else if(f3 == 5) taken = (r1 >= r2)
else if(f3 == 6) taken = (ur1 < ur2)
else if(f3 == 7) taken = (ur1 >= ur2)
else trapout(sprintf("Illegal instruction at 0x%X", pc-4))
pc += (taken ? immval : 4)
}
function amach_imm(opcode, f3, rd, rs1, immval, r1, ur1, shamt) {
r1 = getreg(rs1); ur1 = uint32(r1)
if(opcode == 3) { # load
if(f3 == 0 || f3 == 1 || f3 == 2 || f3 == 4 || f3 == 5) {
setreg(rd, read_mem(r1 + immval, 2^(f3 % 4), f3 < 4))
} else trapout(sprintf("Illegal instruction at 0x%X", pc-4))
} else if(opcode == 19) { # 0x13, immediate arithmetic
shamt = bw_and(immval, 31)
if(f3 == 0) setreg(rd, r1 + immval)
else if(f3 == 4) setreg(rd, bw_xor(r1, immval))
else if(f3 == 6) setreg(rd, bw_or(r1, immval))
else if(f3 == 7) setreg(rd, bw_and(r1, immval))
else if(f3 == 1) setreg(rd, (r1 * (2^shamt)) % 4294967296) # slli
else if(f3 == 5 && immval < 1024) setreg(rd, int(ur1 / (2^shamt))) # srli
else if(f3 == 5 && immval >= 1024) setreg(rd, floor(r1 / (2^shamt))) # srai
else if(f3 == 2) setreg(rd, (r1 < immval) ? 1 : 0)
else if(f3 == 3) setreg(rd, (ur1 < immval) ? 1 : 0)
else trapout(sprintf("Illegal instruction at 0x%X", pc-4))
} else if(opcode == 103) { # 0x67, JALR
setreg(rd, pc)
pc = r1 + immval
} else if(opcode == 115) { # 0x73, system call / csr
if(immval == 0) handle_ecall(getreg(17), getreg(10), getreg(11), getreg(12), getreg(13), getreg(14), getreg(15))
else if(immval == 1) trapout(sprintf("EBREAK at 0x%X", pc-4))
else trapout(sprintf("Unimplemented external system call at 0x%X", pc-4))
} else trapout(sprintf("Illegal instruction at 0x%X", pc-4))
}
# A-extension
function amach_atomic(f3, f5, aq, rl, rd, rs1, rs2, r1, r2, val, uval, ur2) {
r1 = getreg(rs1); r2 = getreg(rs2)
ur2 = uint32(r2)
if(f3 == 2) {
val = read_word(r1)
uval = uint32(val)
if(f5 == 0) { # amoadd.w
setreg(rd, val)
write_word(r1, val + r2)
} else if(f5 == 1) { # amoswap.w
setreg(rd, val)
write_word(r1, r2)
} else if(f5 == 2) { # lr.w
setreg(rd, val)
RES_ADDR = r1
} else if(f5 == 3) { # sc.w
if(RES_ADDR == r1) {
write_word(r1, r2)
setreg(rd, 0)
RES_ADDR = -1
} else setreg(rd, 1)
} else if(f5 == 4) { # amoxor.w
setreg(rd, val)
write_word(r1, bw_xor(val, r2))
} else if(f5 == 8) { # amoor.w
setreg(rd, val)
write_word(r1, bw_or(val, r2))
} else if(f5 == 12) { # amoand.w
setreg(rd, val)
write_word(r1, bw_and(val, r2))
} else if(f5 == 16) { # amomin.w
setreg(rd, val)
write_word(r1, val <= r2 ? val : r2)
} else if(f5 == 20) { # amomax.w
setreg(rd, val)
write_word(r1, val >= r2 ? val : r2)
} else if(f5 == 24) { # amominu.w
setreg(rd, val)
write_word(r1, uval <= ur2 ? val : r2)
} else if(f5 == 28) { # amomaxu.w
setreg(rd, val)
write_word(r1, uval >= ur2 ? val : r2)
} else trapout(sprintf("Unimplemented atomic instruction at 0x%X", pc-4))
} else trapout(sprintf("Illegal atomic instruction at 0x%X", pc-4))
}
# C-extension (compressed instructions) handler
function amach_comp(instr, op, f3, b12, r11_7, r9_7, r6_2, r4_2, shamt, imm, base, val) {
op = instr % 4
f3 = int(instr / 8192) % 8
b12 = int(instr / 4096) % 2
r11_7 = int(instr / 128) % 32
r9_7 = (r11_7 % 8) + 8
r6_2 = int(instr / 4) % 32
r4_2 = (r6_2 % 8) + 8
shamt = r6_2 + b12 * 32
if(op == 0) {
if(f3 == 0) { # C.ADDI4SPN
imm = (r11_7 % 16) * 64 + (int(r11_7 / 16) + b12 * 2) * 16 + (int(r6_2 / 8) % 2) * 8 + (int(r6_2 / 16) % 2) * 4
if(imm == 0) trapout(sprintf("Illegal instruction C.ADDI4SPN at 0x%X", pc-2))
setreg(r4_2, getreg(2) + imm)
} else if(f3 == 2) { # C.LW
imm = (int(r6_2 / 8) % 2) * 64 + (int(r11_7 / 8) % 4) * 8 + b12 * 32 + (int(r6_2 / 16) % 2) * 4
setreg(r4_2, read_mem(getreg(r9_7) + imm, 4, 1))
} else if(f3 == 6) { # C.SW
imm = (int(r6_2 / 8) % 2) * 64 + (int(r11_7 / 8) % 4) * 8 + b12 * 32 + (int(r6_2 / 16) % 2) * 4
write_mem(getreg(r9_7) + imm, getreg(r4_2), 4)
} else trapout(sprintf("Illegal instruction at 0x%X", pc-2))
} else if(op == 1) {
if(f3 == 0) { # C.NOP / C.ADDI
imm = r6_2 + b12 * 32
if(imm >= 32) imm -= 64
setreg(r11_7, getreg(r11_7) + imm)
} else if(f3 == 1 || f3 == 5) { # C.JAL / C.J
imm = b12 * 2048 + (int(r11_7 / 2) % 2) * 1024 + (int(r11_7 / 4) % 4) * 256 + (int(r6_2 / 16) % 2) * 128 + (r11_7 % 2) * 64 + (r6_2 % 2) * 32 + (int(r11_7 / 16)) * 16 + (int(r6_2 / 2) % 8) * 2
if(imm >= 2048) imm -= 4096
if(f3 == 1) setreg(1, pc)
pc = (pc - 2) + imm
} else if(f3 == 2) { # C.LI
imm = r6_2 + b12 * 32
if(imm >= 32) imm -= 64
setreg(r11_7, imm)
} else if(f3 == 3) { # C.ADDI16SP / C.LUI
if(r11_7 == 2) { # C.ADDI16SP
imm = b12 * 512 + (int(r6_2 / 2) % 4) * 128 + (int(r6_2 / 8) % 2) * 64 + (r6_2 % 2) * 32 + (int(r6_2 / 16) % 2) * 16
if(imm >= 512) imm -= 1024
if(imm == 0) trapout(sprintf("Illegal instruction C.ADDI16SP at 0x%X", pc-2))
setreg(2, getreg(2) + imm)
} else if(r11_7 != 0) { # C.LUI
imm = r6_2 + b12 * 32
if(imm >= 32) imm -= 64
imm = imm * 4096
if(imm == 0) trapout(sprintf("Illegal instruction C.LUI at 0x%X", pc-2))
setreg(r11_7, imm)
}
} else if(f3 == 4) {
val = int(r11_7 / 8) % 4
if(val == 0) { # C.SRLI
if(shamt >= 32) trapout(sprintf("Illegal shift amount %d at 0x%X", shamt, pc-2))
imm = getreg(r9_7)
if(imm < 0) imm += 4294967296
setreg(r9_7, int(imm / (2^shamt)))
} else if(val == 1) { # C.SRAI
if(shamt >= 32) trapout(sprintf("Illegal shift amount %d at 0x%X", shamt, pc-2))
setreg(r9_7, floor(getreg(r9_7) / (2^shamt)))
} else if(val == 2) { # C.ANDI
imm = r6_2 + b12 * 32
if(imm >= 32) imm -= 64
setreg(r9_7, bw_and(getreg(r9_7), imm))
} else if(val == 3) { # C.SUB, C.XOR, C.OR, C.AND
imm = int(r6_2 / 8) % 4
if(b12 != 0) trapout(sprintf("Illegal register-register instruction at 0x%X", pc-2))
if(imm == 0) setreg(r9_7, getreg(r9_7) - getreg(r4_2))
else if(imm == 1) setreg(r9_7, bw_xor(getreg(r9_7), getreg(r4_2)))
else if(imm == 2) setreg(r9_7, bw_or(getreg(r9_7), getreg(r4_2)))
else if(imm == 3) setreg(r9_7, bw_and(getreg(r9_7), getreg(r4_2)))
}
} else if(f3 == 6 || f3 == 7) { # C.BEQZ / C.BNEZ
imm = b12 * 256 + (int(r6_2 / 8) % 4) * 64 + (r6_2 % 2) * 32 + (int(r11_7 / 8) % 4) * 8 + (int(r6_2 / 2) % 4) * 2
if(imm >= 256) imm -= 512
val = (f3 == 6) ? (getreg(r9_7) == 0) : (getreg(r9_7) != 0)
pc = val ? (pc - 2) + imm : pc
}
} else if(op == 2) {
if(f3 == 0) { # C.SLLI
if(shamt >= 32) trapout(sprintf("Illegal shift amount %d at 0x%X", shamt, pc-2))
if(r11_7 != 0) {
setreg(r11_7, (getreg(r11_7) * (2^shamt)) % 4294967296)
}
} else if(f3 == 2) { # C.LWSP
if(r11_7 == 0) trapout(sprintf("Illegal instruction C.LWSP with rd=0 at 0x%X", pc-2))
imm = (r6_2 % 4) * 64 + b12 * 32 + (int(r6_2 / 4) % 8) * 4
setreg(r11_7, read_mem(getreg(2) + imm, 4, 1))
} else if(f3 == 4) { # C.JR, C.MV, C.JALR, C.ADD
if(b12 == 0) {
if(r6_2 == 0) { # C.JR
if(r11_7 == 0) trapout(sprintf("Illegal instruction C.JR with rs1=0 at 0x%X", pc-2))
pc = getreg(r11_7)
} else setreg(r11_7, getreg(r6_2)) # C.MV
} else {
if(r6_2 == 0) {
if(r11_7 == 0) trapout(sprintf("EBREAK at 0x%X", pc-2)) # C.EBREAK
else { # C.JALR
imm = getreg(r11_7)
setreg(1, pc)
pc = imm
}
} else setreg(r11_7, getreg(r11_7) + getreg(r6_2)) # C.ADD
}
} else if(f3 == 6) { # C.SWSP
imm = (r11_7 % 4) * 64 + int(r11_7 / 4) * 4 + b12 * 32
write_mem(getreg(2) + imm, getreg(r6_2), 4)
} else trapout(sprintf("Illegal instruction at 0x%X", pc-2))
} else trapout(sprintf("Illegal instruction at 0x%X", pc-2))
}
# main instruction decoding and execution routine
function amach_exec(instr, opcode, rd, rs1, rs2, imm, funct3, funct7) {
if((instr % 4) != 3) {
amach_comp(instr)
return
}
opcode = instr % 128
instr = int(instr / 128)
rd = instr % 32
imm = int(instr / 32)
funct3 = imm % 8
rs1 = int(imm / 8) % 32
rs2 = int(imm / 256) % 32
funct7 = int(imm / 8192)
if(opcode == 51) { # 0x33, register arithmetic, type R
amach_reg_arith(funct3, funct7, rd, rs1, rs2)
} else if(opcode == 47) { # 0x2f, atomic operations, type R
amach_atomic(funct3, int(funct7 / 4), int(funct7 / 2) % 2, funct7 % 2, rd, rs1, rs2)
} else if(opcode == 3 || opcode == 19 || opcode == 103 || opcode == 115) { # type I
amach_imm(opcode, funct3, rd, rs1, imm_sign_ex(rs2 + funct7 * 32))
} else if(opcode == 35) { # 0x23, store, type S
amach_store(funct3, rs1, rs2, imm_sign_ex(rd + funct7 * 32))
} else if(opcode == 99) { # 0x63, branch, type B
imm = rd + (funct7 % 64) * 32 + (rd % 2) * 2047 + int(funct7 / 64) * 4096
pc -= 4
amach_branch(funct3, rs1, rs2, imm_sign_ex_b(imm))
} else if(opcode == 111) { # 0x6F, JAL, type J
setreg(rd, pc)
imm_10_1 = int(rs2 / 2) + (funct7 % 64) * 16
imm_19_12 = funct3 + rs1 * 8
imm = imm_10_1 * 2 + (rs2 % 2) * 2048 + imm_19_12 * 4096 + int(funct7 / 64) * 1048576
if(imm >= 1048576) imm -= 2097152
pc += imm - 4
} else if(opcode == 55) { # 0x37, LUI, type U
setreg(rd, imm * 4096)
} else if(opcode == 23) { # 0x17, AUIPC, type U
setreg(rd, imm * 4096 + pc - 4)
} else if(opcode == 15) { # 0x0F, FENCE, type I / no-op
} else trapout(sprintf("Illegal instruction at 0x%X", pc-4))
}
# Initialization section
BEGIN {
split("", MEM) # init the memory array
split("", REG) # init the (integer) registers
REG[0] = 0 # zero register
REG[2] = 2^31 # stack pointer top
RES_ADDR = -1 # reserved address for atomic ops
LVA = int(LVA)
pc = LVA
NEXT_FD = 3
LAST_SEC = -1
VIRT_NSEC = 0
srand()
}
# Decimal memory collection section
/^[[:space:]]*[[:digit:][:space:]]+/ {for(i=1; i<=NF; i++) MEM[pc++] = int($i)}
# Execution section
END {
memsize = pc - LVA
pc = LVA
while(pc > -1) {
instr = MEM[pc++] + 256 * MEM[pc++]
if((instr % 4) == 3) # full instruction
instr += 65536 * MEM[pc++] + 16777216 * MEM[pc++]
amach_exec(instr) # decode and execute
}
for(fd in FD_PATH) {
if(FD_DIRTY[fd]) {
write_fd_to_file(fd)
}
}
}
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