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#!/usr/bin/env python3
"""Name every DCN register the DMCUB firmware touches, and say which function
touches it, read or write.
How register access actually works in this firmware (this was a wrong turn in the
first pass -- register addresses are *not* l32r literals):
l32r a6, =0x60018030 ; base of a 2057-entry register-address table
l32i a10, a6, 0xe8 ; a10 = absolute register address (0x5ffc____)
l32i a9, a10, 0 ; read | s32i a9, a10, 0 ; write
The table holds absolute addresses in the DMCUB's register aperture. The aperture
is recovered by voting `value = APERTURE + 4*dword_offset` against AMD's published
offsets and then *validating semantically*: at 0x5ffcd300 the table's runs decode
as coherent register blocks (DMCUB_REGION3_CW*, DMCUB_INTERRUPT_*, DMCUB_SCRATCH*,
VPG0_* then VPG1_* in instance order), 1597/2153 values resolve to a known
register and 1446 neighbour pairs share a block prefix. Competing apertures score
strictly worse; see --vote.
usage:
dmcub_regs.py <image> <offset_header> table dump the register table
dmcub_regs.py <image> <offset_header> access [--grep RE] register touches by function
dmcub_regs.py <image> <offset_header> vote aperture evidence + controls
"""
import argparse
import collections
import importlib.util
import os
import re
import struct
HERE = os.path.dirname(os.path.abspath(__file__))
def _load(name):
s = importlib.util.spec_from_file_location(name, os.path.join(HERE, name + '.py'))
m = importlib.util.module_from_spec(s)
s.loader.exec_module(m)
return m
dis = _load('dmcub_dis')
regmap = _load('dmcub_regmap')
APERTURE = 0x5ffcd300
TABLE_LO, TABLE_HI = 0x5f800000, 0x60000000
class Regs:
def __init__(self, image, offsets, aperture=APERTURE):
self.a = dis.Analysis(image)
self.aperture = aperture
self.off2names = collections.defaultdict(list)
for n, (o, seg) in regmap.parse_offsets(offsets).items():
self.off2names[o].append((seg, n))
self.runs = self._runs()
def _runs(self):
p = self.a.img.payload
runs, cur = [], []
for off in range(0, len(p) - 3, 4):
v, = struct.unpack_from('<I', p, off)
if TABLE_LO <= v < TABLE_HI and v % 4 == 0:
cur.append((self.a.img.va(off), v))
else:
if len(cur) >= 8:
runs.append(cur)
cur = []
if len(cur) >= 8:
runs.append(cur)
return runs
def name(self, addr, prefer_seg=None):
if addr is None or addr < self.aperture or (addr - self.aperture) % 4:
return None
cands = self.off2names.get((addr - self.aperture) // 4)
if not cands:
return None
names = [n for seg, n in cands]
return '/'.join(sorted(names, key=lambda n: (0 if n.startswith('DMCUB') else 1, len(n))))
# ---- light abstract interpretation to resolve register accesses ------
def accesses(self):
"""yield (func_va, insn_va, 'R'|'W', reg_addr, name)"""
tablebases = set()
for r in self.runs:
tablebases.add(r[0][0])
out = []
for fva in sorted(self.a.funcs):
# val[reg] = ('lit', v) | ('regptr', addr)
val = {}
for x in self.a.dis(fva):
parts = [p.strip() for p in x.op_str.split(',')]
m = x.mnemonic
if m == 'l32r':
v = self.a.lit(x)
val[parts[0]] = ('lit', v)
continue
if m in ('mov', 'mov.n') and len(parts) == 2:
if parts[1] in val:
val[parts[0]] = val[parts[1]]
else:
val.pop(parts[0], None)
continue
if m in ('l32i', 'l32i.n') and len(parts) == 3:
dst, base = parts[0], parts[1]
try:
off = int(parts[2], 0)
except ValueError:
off = None
b = val.get(base)
if b and b[0] == 'lit' and b[1] is not None and off is not None:
w = self.a.img.word(b[1] + off)
if w is not None and TABLE_LO <= w < TABLE_HI:
val[dst] = ('regptr', w)
continue
if b and b[0] == 'regptr' and off == 0:
out.append((fva, x.address, 'R', b[1], self.name(b[1])))
val.pop(dst, None)
continue
if m in ('s32i', 's32i.n') and len(parts) == 3:
base = parts[1]
try:
off = int(parts[2], 0)
except ValueError:
off = None
b = val.get(base)
if b and b[0] == 'regptr' and off == 0:
out.append((fva, x.address, 'W', b[1], self.name(b[1])))
continue
# anything else kills the destination
if parts and re.fullmatch(r'a\d+', parts[0]):
val.pop(parts[0], None)
return out
def vote(r, offsets):
"""Aperture evidence with controls: score candidates by named-fraction and
block-prefix coherence of neighbours in the register tables."""
vals = [v for run in r.runs for _, v in run]
votes = collections.Counter()
offs = set(r.off2names)
for v in vals[:800]:
for o in offs:
votes[v - 4 * o] += 1
cands = [a for a, _ in votes.most_common(200)]
def prefix(n):
return n.split('_')[0]
def score(A):
named = coh = 0
for run in r.runs:
prev = None
for _, v in run:
if v < A or (v - A) % 4:
prev = None
continue
c = r.off2names.get((v - A) // 4)
if not c:
prev = None
continue
named += 1
pfx = set(prefix(n) for _, n in c)
if prev and prev & pfx:
coh += 1
prev = pfx
return named, coh
rows = sorted(((score(A), A) for A in cands), reverse=True)
print('register-address values in tables: %d (%d distinct)' % (len(vals), len(set(vals))))
for (named, coh), A in rows[:6]:
print(' aperture 0x%08x named %d/%d (%.0f%%) coherent-neighbour pairs %d%s' % (
A, named, len(vals), 100.0 * named / len(vals), coh,
' <= used' if A == r.aperture else ''))
def main():
ap = argparse.ArgumentParser()
ap.add_argument('image')
ap.add_argument('offsets')
ap.add_argument('cmd', choices=['table', 'access', 'vote'])
ap.add_argument('--grep', default=None)
ap.add_argument('--aperture', default=hex(APERTURE))
args = ap.parse_args()
r = Regs(args.image, args.offsets, int(args.aperture, 0))
if args.cmd == 'vote':
vote(r, args.offsets)
return
if args.cmd == 'table':
for run in r.runs:
print('=== table @VA 0x%08x n=%d' % (run[0][0], len(run)))
for va, v in run:
n = r.name(v)
if args.grep and not (n and re.search(args.grep, n)):
continue
print(' [0x%03x] 0x%08x %s' % (va - run[0][0], v, n or '?'))
return
acc = r.accesses()
byreg = collections.defaultdict(list)
for fva, ia, rw, addr, name in acc:
byreg[(addr, name)].append((fva, ia, rw))
print('resolved register accesses: %d (%d distinct registers)' % (len(acc), len(byreg)))
for (addr, name), uses in sorted(byreg.items(), key=lambda kv: (kv[0][1] or '', kv[0][0])):
if args.grep and not (name and re.search(args.grep, name)):
continue
rd = sum(1 for _, _, rw in uses if rw == 'R')
wr = len(uses) - rd
print(' 0x%08x %-44s R=%-3d W=%-3d %s' % (
addr, name or '?', rd, wr,
' '.join(sorted(set('0x%08x' % f for f, _, _ in uses)))))
if __name__ == '__main__':
main()
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