1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
|
from rpython.rlib import _rffi_stacklet as _c
from rpython.rlib.debug import ll_assert
from rpython.rtyper.annlowlevel import llhelper
from rpython.rtyper.lltypesystem import lltype, llmemory
from rpython.rtyper.lltypesystem.lloperation import llop
from rpython.tool.staticmethods import StaticMethods
NULL_SUSPSTACK = lltype.nullptr(llmemory.GCREF.TO)
def _new_callback(h, arg):
# We still have the old shadowstack active at this point; save it
# away, and start a fresh new one
oldsuspstack = gcrootfinder.oldsuspstack
h = llmemory.cast_ptr_to_adr(h)
llop.gc_save_current_state_away(lltype.Void,
oldsuspstack, h)
llop.gc_start_fresh_new_state(lltype.Void)
gcrootfinder.oldsuspstack = NULL_SUSPSTACK
#
newsuspstack = gcrootfinder.callback(oldsuspstack, arg)
#
# Finishing this stacklet.
gcrootfinder.oldsuspstack = NULL_SUSPSTACK
gcrootfinder.newsuspstack = newsuspstack
h = llop.gc_shadowstackref_context(llmemory.Address, newsuspstack)
return llmemory.cast_adr_to_ptr(h, _c.handle)
def prepare_old_suspstack():
if not gcrootfinder.oldsuspstack: # else reuse the one still there
_allocate_old_suspstack()
def _allocate_old_suspstack():
suspstack = llop.gc_shadowstackref_new(llmemory.GCREF)
gcrootfinder.oldsuspstack = suspstack
_allocate_old_suspstack._dont_inline_ = True
def get_result_suspstack(h):
# Now we are in the target, after the switch() or the new().
# Note that this whole module was carefully written in such a way as
# not to invoke pushing/popping things off the shadowstack at
# unexpected moments...
oldsuspstack = gcrootfinder.oldsuspstack
newsuspstack = gcrootfinder.newsuspstack
gcrootfinder.oldsuspstack = NULL_SUSPSTACK
gcrootfinder.newsuspstack = NULL_SUSPSTACK
if not h:
raise MemoryError
# We still have the old shadowstack active at this point; save it
# away, and restore the new one
if oldsuspstack:
ll_assert(not _c.is_empty_handle(h),"unexpected empty stacklet handle")
h = llmemory.cast_ptr_to_adr(h)
llop.gc_save_current_state_away(lltype.Void, oldsuspstack, h)
else:
ll_assert(_c.is_empty_handle(h),"unexpected non-empty stacklet handle")
llop.gc_forget_current_state(lltype.Void)
#
llop.gc_restore_state_from(lltype.Void, newsuspstack)
#
# From this point on, 'newsuspstack' is consumed and done, its
# shadow stack installed as the current one. It should not be
# used any more. For performance, we avoid it being deallocated
# by letting it be reused on the next switch.
gcrootfinder.oldsuspstack = newsuspstack
# Return.
return oldsuspstack
class StackletGcRootFinder:
__metaclass__ = StaticMethods
def new(thrd, callback, arg):
gcrootfinder.callback = callback
thread_handle = thrd._thrd
prepare_old_suspstack()
h = _c.new(thread_handle, llhelper(_c.run_fn, _new_callback), arg)
return get_result_suspstack(h)
new._dont_inline_ = True
def switch(suspstack):
# suspstack has a handle to target, i.e. where to switch to
ll_assert(suspstack != gcrootfinder.oldsuspstack,
"stacklet: invalid use")
gcrootfinder.newsuspstack = suspstack
h = llop.gc_shadowstackref_context(llmemory.Address, suspstack)
h = llmemory.cast_adr_to_ptr(h, _c.handle)
prepare_old_suspstack()
h = _c.switch(h)
return get_result_suspstack(h)
switch._dont_inline_ = True
def is_empty_handle(suspstack):
return not suspstack
def get_null_handle():
return NULL_SUSPSTACK
gcrootfinder = StackletGcRootFinder()
gcrootfinder.oldsuspstack = NULL_SUSPSTACK
gcrootfinder.newsuspstack = NULL_SUSPSTACK
|
