Introduced 'as_signed' utility method for turning unsigned values int…

…o signed ones

qiling/os/posix/syscall/mman.py

@@ -161,7 +161,7 @@ class mmap_flags(IntFlag):
         label = '[mmap anonymous]'
 
     else:
-        fd = ql.unpacks(ql.pack(fd))
+        fd = ql.os.utils.as_signed(fd, 32)
 
         if fd not in range(NR_OPEN):
             return -EBADF

qiling/os/posix/syscall/unistd.py

@@ -266,7 +266,7 @@ def ql_syscall_faccessat(ql: Qiling, dirfd: int, filename: int, mode: int):
 
 
 def ql_syscall_lseek(ql: Qiling, fd: int, offset: int, origin: int):
-    offset = ql.unpacks(ql.pack(offset))
+    offset = ql.os.utils.as_signed(offset, 32)
 
     f = get_opened_fd(ql.os, fd)
 
@@ -285,8 +285,7 @@ def ql_syscall_lseek(ql: Qiling, fd: int, offset: int, origin: int):
 
 
 def ql_syscall__llseek(ql: Qiling, fd: int, offset_high: int, offset_low: int, result: int, whence: int):
-    # treat offset as a signed value
-    offset = ql.unpack64s(ql.pack64((offset_high << 32) | offset_low))
+    offset = ql.os.utils.as_signed((offset_high << 32) | offset_low, 64)
 
     f = get_opened_fd(ql.os, fd)
 

qiling/os/posix/syscall/wait.py

@@ -9,19 +9,15 @@
 from qiling.os.posix.const import ECHILD
 
 def ql_syscall_wait4(ql: Qiling, pid: int, wstatus: int, options: int, rusage: int):
-    # convert to signed (pid_t is 32bit)
-    pid = ql.unpack32s(ql.pack32(pid))
-    # python expects options to be a signed 32bit int
-    options = ql.unpack32s(ql.pack32(options))
+    pid = ql.os.utils.as_signed(pid, 32)
+    options = ql.os.utils.as_signed(options, 32)
 
     try:
         spid, status, _ = os.wait4(pid, options)
-
-        if wstatus:
-            ql.mem.write_ptr(wstatus, status, 4)
-
-        retval = spid
     except ChildProcessError:
-        retval = -ECHILD
+        return -ECHILD
+
+    if wstatus:
+        ql.mem.write_ptr(wstatus, status, 4)
 
-    return retval
+    return spid

qiling/os/utils.py

@@ -23,6 +23,25 @@ class QlOsUtils:
     def __init__(self, ql: Qiling):
         self.ql = ql
 
+    @staticmethod
+    def as_signed(value: int, nbits: int) -> int:
+        """Transform an unsigned integer value into its 2's complement signed value
+        equivalent. This method has no effect on signed integers.
+
+        Args:
+            value: an unsigned integer to transform
+            nbits: value bit size
+
+        Returns: a signed integer
+        """
+
+        # truncate value to specified bit size
+        value &= (1 << nbits) - 1
+
+        msb = 1 << (nbits - 1)
+
+        return -(value & ~(msb - 1)) | value
+
     def read_string(self, address: int, encoding: str, maxlen: int = 0) -> str:
         """Read a null-terminated string from memory.
 
@@ -244,4 +263,4 @@ def __update_ellipsis(self, args: Iterable[int]) -> Callable[[MutableMapping], N
         def __do_update(params: MutableMapping) -> None:
             params.update((f'{QlOsUtils.ELLIPSIS_PREF}{i}', a) for i, a in enumerate(args))
 
-        return __do_update
+        return __do_update

qiling/os/windows/dlls/kernel32/fileapi.py

@@ -698,7 +698,7 @@ def _CreateFileMapping(ql: Qiling, address: int, params):
 
     req_size = (dwMaximumSizeHigh << 32) | dwMaximumSizeLow
 
-    if hFile == ql.unpack(ql.packs(INVALID_HANDLE_VALUE)):
+    if hFile == ql.os.utils.as_signed(INVALID_HANDLE_VALUE, ql.arch.bits):
         fmobj = FileMappingMem()
 
     else: