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# gdb script: catch the write that ZEROES ds+0xe94 after the CASE1 body set
# it to 0x18. Run via run_cycle.sh gdb-launch (device init happens during
# cuInit, before the CDT_PAUSE).
#
# bpz18 showed: CASE1 (0x32e8be) hit at t=0.24; at FUN_003e3e80 (t=72.9)
# ds+0xe94 == 0. Set a hardware watchpoint at the CASE1 hit and log every
# write with a backtrace.
import gdb
import time
gdb.execute("set pagination off")
gdb.execute("set confirm off")
gdb.execute("set environment CDT_PAUSE=60")
gdb.execute("set environment CDT_HOLD=900")
gdb.execute("catch load libcuda.so")
gdb.execute("run")
out = gdb.execute("info proc mappings", to_string=True)
base = None
for line in out.splitlines():
if "libcuda" in line and "r-xp" in line:
f = line.split()
base = int(f[0], 16) - int(f[3], 16)
break
print("BASE=0x%x" % (base or 0))
if base is None:
raise SystemExit
CASE1 = base + 0x32e8be
TERM = base + 0x2e3e80
CALLER_RET = base + 0xd0eae1
gdb.execute("break *0x%x" % CASE1)
gdb.execute("break *0x%x" % TERM)
def rd(addr, n=4, fmt="unsigned int"):
try:
return int(gdb.parse_and_eval("*(%s*)0x%x" % (fmt, addr))) & ((1 << (8 * n)) - 1)
except Exception:
return None
t0 = time.time()
watched = False
for hit in range(200):
try:
gdb.execute("continue")
except gdb.error as e:
print("CONTINUE_END %s" % e)
break
rip = int(gdb.parse_and_eval("$rip")) & 0xffffffffffffffff
if rip == CASE1 and not watched:
rc = int(gdb.parse_and_eval("$rcx")) & 0xffffffffffffffff
gdb.execute("delete 1")
gdb.execute("set $wpaddr = 0x%x" % (rc + 0xe94))
gdb.execute("watch *(int*)$wpaddr")
watched = True
print("WATCH set on ds=0x%x +0xe94 (t=%.3f)" % (rc, time.time() - t0))
continue
if rip == TERM:
ret = rd(int(gdb.parse_and_eval("$rsp")), 8, "unsigned long")
if ret != CALLER_RET:
continue
rdi = int(gdb.parse_and_eval("$rdi")) & 0xffffffffffffffff
ds = rd(rdi + 0x40, 8, "unsigned long")
print("TERMINATOR t=%.3f ds=0x%x e94=0x%x c4c=0x%x" %
(time.time() - t0, ds or 0, rd(ds + 0xe94) or 0, rd(ds + 0xc4c) or 0))
break
# watchpoint hit
addr = int(gdb.parse_and_eval("$wpaddr")) & 0xffffffffffffffff
val = rd(addr) or 0
print("WP hit t=%.3f pc=+0x%x val=0x%x" % (time.time() - t0, rip - base, val))
try:
print(gdb.execute("bt 6", to_string=True))
except Exception:
pass
try:
gdb.execute("detach")
except Exception:
pass
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