Author: Armin Rigo <ar...@tunes.org>
Branch: shadowstack-no-move-2
Changeset: r79827:c137e4ccaacd
Date: 2015-09-25 16:46 +0200
http://bitbucket.org/pypy/pypy/changeset/c137e4ccaacd/
Log: Backout the issue #2017 fixes, now that they are not really needed
any more. This should indirectly fix issue #2141.
diff --git a/rpython/memory/gctransform/shadowstack.py
b/rpython/memory/gctransform/shadowstack.py
--- a/rpython/memory/gctransform/shadowstack.py
+++ b/rpython/memory/gctransform/shadowstack.py
@@ -180,7 +180,7 @@
thread_stacks[gcdata.active_tid] = old_ref
#
# no GC operation from here -- switching shadowstack!
- shadow_stack_pool.save_current_state_away(old_ref, llmemory.NULL)
+ shadow_stack_pool.save_current_state_away(old_ref)
if new_ref:
shadow_stack_pool.restore_state_from(new_ref)
else:
@@ -225,18 +225,11 @@
# ____________________________________________________________
class ShadowStackPool(object):
- """Manages a pool of shadowstacks. The MAX most recently used
- shadowstacks are fully allocated and can be directly jumped into
- (called "full stacks" below).
- The rest are stored in a more virtual-memory-friendly way, i.e.
- with just the right amount malloced. Before they can run, they
- must be copied into a full shadowstack.
+ """Manages a pool of shadowstacks.
"""
_alloc_flavor_ = "raw"
root_stack_depth = 163840
- MAX = 20
-
def __init__(self, gcdata):
self.unused_full_stack = llmemory.NULL
self.gcdata = gcdata
@@ -249,28 +242,18 @@
"""Allocate an empty SHADOWSTACKREF object."""
return lltype.malloc(SHADOWSTACKREF, zero=True)
- def save_current_state_away(self, shadowstackref, ncontext):
+ def save_current_state_away(self, shadowstackref):
"""Save the current state away into 'shadowstackref'.
This either works, or raise MemoryError and nothing is done.
To do a switch, first call save_current_state_away() or
forget_current_state(), and then call restore_state_from()
or start_fresh_new_state().
"""
- fresh_free_fullstack = shadowstackref.prepare_free_slot()
- if self.unused_full_stack:
- if fresh_free_fullstack:
- llmemory.raw_free(fresh_free_fullstack)
- elif fresh_free_fullstack:
- self.unused_full_stack = fresh_free_fullstack
- else:
- self._prepare_unused_stack()
- #
+ self._prepare_unused_stack()
shadowstackref.base = self.gcdata.root_stack_base
shadowstackref.top = self.gcdata.root_stack_top
- shadowstackref.context = ncontext
ll_assert(shadowstackref.base <= shadowstackref.top,
"save_current_state_away: broken shadowstack")
- shadowstackref.attach()
#
# cannot use llop.gc_writebarrier() here, because
# we are in a minimally-transformed GC helper :-/
@@ -293,7 +276,6 @@
ll_assert(bool(shadowstackref.base), "empty shadowstackref!")
ll_assert(shadowstackref.base <= shadowstackref.top,
"restore_state_from: broken shadowstack")
- self.unused_full_stack = shadowstackref.rebuild(self.unused_full_stack)
self.gcdata.root_stack_base = shadowstackref.base
self.gcdata.root_stack_top = shadowstackref.top
self._cleanup(shadowstackref)
@@ -306,127 +288,28 @@
def _cleanup(self, shadowstackref):
shadowstackref.base = llmemory.NULL
shadowstackref.top = llmemory.NULL
- shadowstackref.context = llmemory.NULL
def _prepare_unused_stack(self):
- ll_assert(self.unused_full_stack == llmemory.NULL,
- "already an unused_full_stack")
- root_stack_size = sizeofaddr * self.root_stack_depth
- self.unused_full_stack = llmemory.raw_malloc(root_stack_size)
if self.unused_full_stack == llmemory.NULL:
- raise MemoryError
+ root_stack_size = sizeofaddr * self.root_stack_depth
+ self.unused_full_stack = llmemory.raw_malloc(root_stack_size)
+ if self.unused_full_stack == llmemory.NULL:
+ raise MemoryError
def get_shadowstackref(root_walker, gctransformer):
if hasattr(gctransformer, '_SHADOWSTACKREF'):
return gctransformer._SHADOWSTACKREF
- # Helpers to same virtual address space by limiting to MAX the
- # number of full shadow stacks. If there are more, we compact
- # them into a separately-allocated zone of memory of just the right
- # size. See the comments in the definition of fullstack_cache below.
-
- def ll_prepare_free_slot(_unused):
- """Free up a slot in the array of MAX entries, ready for storing
- a new shadowstackref. Return the memory of the now-unused full
- shadowstack.
- """
- index = fullstack_cache[0]
- if index > 0:
- return llmemory.NULL # there is already at least one free slot
- #
- # make a compact copy in one old entry and return the
- # original full-sized memory
- index = -index
- ll_assert(index > 0, "prepare_free_slot: cache[0] == 0")
- compacting = lltype.cast_int_to_ptr(SHADOWSTACKREFPTR,
- fullstack_cache[index])
- index += 1
- if index >= ShadowStackPool.MAX:
- index = 1
- fullstack_cache[0] = -index # update to the next value in order
- #
- compacting.detach()
- original = compacting.base
- size = compacting.top - original
- new = llmemory.raw_malloc(size)
- if new == llmemory.NULL:
- return llmemory.NULL
- llmemory.raw_memcopy(original, new, size)
- compacting.base = new
- compacting.top = new + size
- return original
-
- def ll_attach(shadowstackref):
- """After prepare_free_slot(), store a shadowstackref in that slot."""
- index = fullstack_cache[0]
- ll_assert(index > 0, "fullstack attach: no free slot")
- fullstack_cache[0] = fullstack_cache[index]
- fullstack_cache[index] = lltype.cast_ptr_to_int(shadowstackref)
- ll_assert(shadowstackref.fsindex == 0, "fullstack attach: already
one?")
- shadowstackref.fsindex = index # > 0
-
- def ll_detach(shadowstackref):
- """Detach a shadowstackref from the array of MAX entries."""
- index = shadowstackref.fsindex
- ll_assert(index > 0, "detach: unattached shadowstackref")
- ll_assert(fullstack_cache[index] ==
- lltype.cast_ptr_to_int(shadowstackref),
- "detach: bad fullstack_cache")
- shadowstackref.fsindex = 0
- fullstack_cache[index] = fullstack_cache[0]
- fullstack_cache[0] = index
-
- def ll_rebuild(shadowstackref, fullstack_base):
- if shadowstackref.fsindex > 0:
- shadowstackref.detach()
- return fullstack_base
- else:
- # make an expanded copy of the compact shadowstack stored in
- # 'shadowstackref' and free that
- compact = shadowstackref.base
- size = shadowstackref.top - compact
- shadowstackref.base = fullstack_base
- shadowstackref.top = fullstack_base + size
- llmemory.raw_memcopy(compact, fullstack_base, size)
- llmemory.raw_free(compact)
- return llmemory.NULL
-
SHADOWSTACKREFPTR = lltype.Ptr(lltype.GcForwardReference())
SHADOWSTACKREF = lltype.GcStruct('ShadowStackRef',
- ('base', llmemory.Address),
- ('top', llmemory.Address),
- ('context', llmemory.Address),
- ('fsindex', lltype.Signed),
- rtti=True,
- adtmeths={'prepare_free_slot': ll_prepare_free_slot,
- 'attach': ll_attach,
- 'detach': ll_detach,
- 'rebuild': ll_rebuild})
+ ('base', llmemory.Address),
+ ('top', llmemory.Address),
+ rtti=True)
SHADOWSTACKREFPTR.TO.become(SHADOWSTACKREF)
- # Items 1..MAX-1 of the following array can be SHADOWSTACKREF
- # addresses cast to integer. Or, they are small numbers and they
- # make up a free list, rooted in item 0, which goes on until
- # terminated with a negative item. This negative item gives (the
- # opposite of) the index of the entry we try to remove next.
- # Initially all items are in this free list and the end is '-1'.
- fullstack_cache = lltype.malloc(lltype.Array(lltype.Signed),
- ShadowStackPool.MAX,
- flavor='raw', immortal=True)
- for i in range(len(fullstack_cache) - 1):
- fullstack_cache[i] = i + 1
- fullstack_cache[len(fullstack_cache) - 1] = -1
-
def customtrace(gc, obj, callback, arg):
obj = llmemory.cast_adr_to_ptr(obj, SHADOWSTACKREFPTR)
- index = obj.fsindex
- if index > 0:
- # Haaaaaaack: fullstack_cache[] is just an integer, so it
- # doesn't follow the SHADOWSTACKREF when it moves. But we
- # know this customtrace() will be called just after the
- # move. So we fix the fullstack_cache[] now... :-/
- fullstack_cache[index] = lltype.cast_ptr_to_int(obj)
addr = obj.top
start = obj.base
while addr != start:
@@ -440,22 +323,10 @@
(SHADOWSTACKREF, customtrace))
def shadowstack_destructor(shadowstackref):
- if root_walker.stacklet_support:
- from rpython.rlib import _rffi_stacklet as _c
- h = shadowstackref.context
- h = llmemory.cast_adr_to_ptr(h, _c.handle)
- shadowstackref.context = llmemory.NULL
- #
- if shadowstackref.fsindex > 0:
- shadowstackref.detach()
base = shadowstackref.base
shadowstackref.base = llmemory.NULL
shadowstackref.top = llmemory.NULL
llmemory.raw_free(base)
- #
- if root_walker.stacklet_support:
- if h:
- _c.destroy(h)
destrptr = gctransformer.annotate_helper(shadowstack_destructor,
[SHADOWSTACKREFPTR], lltype.Void)
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