def _alloc_C_libcall(self, size, ctype):
if not self.available():
raise RuntimeError("Couldn't find `libc`'s `posix_memalign` to "
"allocate memory")
pagesize = self.lib.getpagesize()
assert self.padding_bytes % pagesize == 0
npages_pad = self.padding_bytes // pagesize
nbytes_user = size * ctypes.sizeof(ctype)
npages_user = (nbytes_user + pagesize - 1) // pagesize
npages_alloc = 2 * npages_pad + npages_user
c_bytesize = ctypes.c_ulong(npages_alloc * pagesize)
c_pointer = ctypes.cast(ctypes.c_void_p(), ctypes.c_void_p)
alignment = self.lib.getpagesize()
ret = self.lib.posix_memalign(ctypes.byref(c_pointer), alignment,
c_bytesize)
if ret != 0:
return None, None
# generate pointers to the left padding, the user data, and the right pad
padleft_pointer = c_pointer
c_pointer = ctypes.c_void_p(c_pointer.value + self.padding_bytes)
padright_pointer = ctypes.c_void_p(c_pointer.value +
npages_user * pagesize)
# and set the permissions on the pad memory to 0 (no access)
# if these fail, don't worry about failing the entire allocation
c_padsize = ctypes.c_ulong(self.padding_bytes)
if self.lib.mprotect(padleft_pointer, c_padsize, ctypes.c_int(0)):
logger.warning("couldn't protect memory")
if self.lib.mprotect(padright_pointer, c_padsize, ctypes.c_int(0)):
logger.warning("couldn't protect memory")
# if there is a multiple of 4 bytes left, use the code below to poison
# the memory
if nbytes_user % 4 == 0:
poison_size = npages_user * pagesize - nbytes_user
intp_type = ctypes.POINTER(ctypes.c_int)
poison_ptr = ctypes.cast(
ctypes.c_void_p(c_pointer.value + nbytes_user), intp_type)
# for both float32 and float64, a sequence of -100 int32s represents NaNs,
# at least on little-endian architectures. It shouldn't matter what we
# put in there, anyway
for i in range(poison_size // 4):
poison_ptr[i] = -100
return c_pointer, (padleft_pointer, c_bytesize)
def _alloc_C_libcall(self, size, ctype):
if not self.available():
raise RuntimeError("Couldn't find `libc`'s `posix_memalign` to "
"allocate memory")
pagesize = self.lib.getpagesize()
assert self.padding_bytes % pagesize == 0
npages_pad = self.padding_bytes // pagesize
nbytes_user = size * ctypes.sizeof(ctype)
npages_user = (nbytes_user + pagesize - 1) // pagesize
npages_alloc = 2*npages_pad + npages_user
c_bytesize = ctypes.c_ulong(npages_alloc * pagesize)
c_pointer = ctypes.cast(ctypes.c_void_p(), ctypes.c_void_p)
alignment = self.lib.getpagesize()
ret = self.lib.posix_memalign(ctypes.byref(c_pointer), alignment, c_bytesize)
if ret != 0:
return None, None
# generate pointers to the left padding, the user data, and the right pad
padleft_pointer = c_pointer
c_pointer = ctypes.c_void_p(c_pointer.value + self.padding_bytes)
padright_pointer = ctypes.c_void_p(c_pointer.value + npages_user * pagesize)
# and set the permissions on the pad memory to 0 (no access)
# if these fail, don't worry about failing the entire allocation
c_padsize = ctypes.c_ulong(self.padding_bytes)
if self.lib.mprotect(padleft_pointer, c_padsize, ctypes.c_int(0)):
logger.warning("couldn't protect memory")
if self.lib.mprotect(padright_pointer, c_padsize, ctypes.c_int(0)):
logger.warning("couldn't protect memory")
# if there is a multiple of 4 bytes left, use the code below to poison
# the memory
if nbytes_user % 4 == 0:
poison_size = npages_user*pagesize - nbytes_user
intp_type = ctypes.POINTER(ctypes.c_int)
poison_ptr = ctypes.cast(ctypes.c_void_p(c_pointer.value + nbytes_user),
intp_type)
# for both float32 and float64, a sequence of -100 int32s represents NaNs,
# at least on little-endian architectures. It shouldn't matter what we
# put in there, anyway
for i in range(poison_size // 4):
poison_ptr[i] = -100
return c_pointer, (padleft_pointer, c_bytesize)