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Make accessing Debugger registers more ergonomic #997

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Make accessing Debugger registers more ergonomic #997

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0149e40
cptbox: add array-like register accessors
Xyene Feb 27, 2022
d6c7393
cptbox/isolate: use array accessors for uargs
Xyene Feb 27, 2022
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6 changes: 6 additions & 0 deletions dmoj/cptbox/_cptbox.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,10 @@ PTBOX_ABI_COUNT: int
ALL_ABIS: List[int]
SUPPORTED_ABIS: List[int]

class ArgAccessor:
def __getitem__(self, reg : int) -> int: ...
def __setitem__(self, reg : int, val : int) -> None: ...

class Debugger:
syscall: int
result: int
Expand All @@ -22,6 +26,7 @@ class Debugger:
arg3: int
arg4: int
arg5: int
arg: ArgAccessor

uresult: int
uarg0: int
Expand All @@ -30,6 +35,7 @@ class Debugger:
uarg3: int
uarg4: int
uarg5: int
uarg: ArgAccessor

pid: int
tid: int
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18 changes: 18 additions & 0 deletions dmoj/cptbox/_cptbox.pyx
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Expand Up @@ -225,6 +225,22 @@ def memory_fd_seal(int fd):

cdef class Process

cdef class Debugger

cdef class ArgAccessor:
cdef Debugger debugger
cdef object base

def __cinit__(self, Debugger debugger, object base):
self.debugger = debugger
self.base = base

def __getitem__(self, reg):
return getattr(self.debugger, '%s%d' % (self.base, reg))
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Why are you doing this in _cptbox? Maybe you should move this into AdvancedDebugger instead.


def __setitem__(self, reg, val):
setattr(self.debugger, '%s%d' % (self.base, reg), val)


cdef class Debugger:
cdef pt_debugger *thisptr
Expand All @@ -235,6 +251,8 @@ cdef class Debugger:
self.thisptr = new pt_debugger()
self.process = process
self.on_return_callback = {}
self.uarg = ArgAccessor(self, "uarg")
self.arg = ArgAccessor(self, "arg")

def __dealloc__(self):
del self.thisptr
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9 changes: 4 additions & 5 deletions dmoj/cptbox/isolate.py
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Expand Up @@ -213,7 +213,7 @@ def _compile_fs_jail(self, fs) -> FilesystemPolicy:

def _dirfd_getter_from_reg(self, reg: int) -> DirFDGetter:
def getter(debugger: Debugger) -> int:
return getattr(debugger, 'uarg%d' % reg)
return debugger.uarg[reg]

return getter

Expand All @@ -222,7 +222,7 @@ def _dirfd_getter_cwd(self, debugger: Debugger) -> int:

def _fs_jail_getter_from_open_flags_reg(self, reg: int) -> FSJailGetter:
def getter(debugger: Debugger) -> FilesystemPolicy:
open_flags = getattr(debugger, 'uarg%d' % reg)
open_flags = debugger.uarg[reg]
for flag in open_write_flags:
# Strict equality is necessary here, since e.g. O_TMPFILE has multiple bits set,
# and O_DIRECTORY & O_TMPFILE > 0.
Expand Down Expand Up @@ -282,7 +282,7 @@ def check(debugger: Debugger) -> None:
# We already allowed this one way or another, don't check again.
return

dirfd = getattr(debugger, 'uarg%d' % dir_reg)
dirfd = debugger.uarg[dir_reg]
full_path = self.get_full_path_unnormalized(debugger, rel_file, dirfd=dirfd)
self._access_check(debugger, full_path, self.read_fs_jail)

Expand All @@ -299,9 +299,8 @@ def check(debugger: Debugger) -> None:
return check

def get_rel_file(self, debugger: Debugger, *, reg: int) -> str:
ptr = getattr(debugger, 'uarg%d' % reg)
try:
file = debugger.readstr(ptr)
file = debugger.readstr(debugger.uarg[reg])
except MaxLengthExceeded as e:
raise DeniedSyscall(ACCESS_ENAMETOOLONG, f'Overly long path: {e.args[0]}')
except UnicodeDecodeError as e:
Expand Down