Author: Armin Rigo <ar...@tunes.org>
Branch:
Changeset: r1017:ddbc16971682
Date: 2014-03-15 11:11 +0100
http://bitbucket.org/pypy/stmgc/changeset/ddbc16971682/
Log: shadowstack: improve the aliasing analysis in the C code.
diff --git a/c7/stm/core.h b/c7/stm/core.h
--- a/c7/stm/core.h
+++ b/c7/stm/core.h
@@ -150,7 +150,7 @@
/* In case of abort, we restore the 'shadowstack' field and the
'thread_local_obj' field. */
- object_t **shadowstack_at_start_of_transaction;
+ struct stm_shadowentry_s *shadowstack_at_start_of_transaction;
object_t *threadlocal_at_start_of_transaction;
/* For debugging */
diff --git a/c7/stm/gcpage.c b/c7/stm/gcpage.c
--- a/c7/stm/gcpage.c
+++ b/c7/stm/gcpage.c
@@ -397,11 +397,11 @@
if (must_be_zero == (segment_base == get_segment_base(0))) {
- object_t **current = tl->shadowstack;
- object_t **base = tl->shadowstack_base;
+ struct stm_shadowentry_s *current = tl->shadowstack;
+ struct stm_shadowentry_s *base = tl->shadowstack_base;
while (current-- != base) {
- assert(*current != (object_t *)-1);
- mark_visit_object(*current, segment_base);
+ assert(current->ss != (object_t *)-1);
+ mark_visit_object(current->ss, segment_base);
}
mark_visit_object(tl->thread_local_obj, segment_base);
}
diff --git a/c7/stm/nursery.c b/c7/stm/nursery.c
--- a/c7/stm/nursery.c
+++ b/c7/stm/nursery.c
@@ -158,11 +158,11 @@
static void collect_roots_in_nursery(void)
{
stm_thread_local_t *tl = STM_SEGMENT->running_thread;
- object_t **current = tl->shadowstack;
- object_t **base = tl->shadowstack_base;
+ struct stm_shadowentry_s *current = tl->shadowstack;
+ struct stm_shadowentry_s *base = tl->shadowstack_base;
while (current-- != base) {
- assert(*current != (object_t *)-1);
- minor_trace_if_young(current);
+ assert(current->ss != (object_t *)-1);
+ minor_trace_if_young(¤t->ss);
}
minor_trace_if_young(&tl->thread_local_obj);
}
diff --git a/c7/stm/setup.c b/c7/stm/setup.c
--- a/c7/stm/setup.c
+++ b/c7/stm/setup.c
@@ -118,7 +118,8 @@
void _init_shadow_stack(stm_thread_local_t *tl)
{
- object_t **s = (object_t **)malloc(SHADOW_STACK_SIZE * sizeof(object_t *));
+ struct stm_shadowentry_s *s = (struct stm_shadowentry_s *)
+ malloc(SHADOW_STACK_SIZE * sizeof(struct stm_shadowentry_s));
assert(s);
tl->shadowstack = s;
tl->shadowstack_base = s;
diff --git a/c7/stmgc.h b/c7/stmgc.h
--- a/c7/stmgc.h
+++ b/c7/stmgc.h
@@ -48,9 +48,15 @@
};
#define STM_SEGMENT ((stm_segment_info_t *)4352)
+struct stm_shadowentry_s {
+ /* Like stm_read_marker_s, this is a struct to enable better
+ aliasing analysis in the C code. */
+ object_t *ss;
+};
+
typedef struct stm_thread_local_s {
/* every thread should handle the shadow stack itself */
- object_t **shadowstack, **shadowstack_base;
+ struct stm_shadowentry_s *shadowstack, *shadowstack_base;
/* a generic optional thread-local object */
object_t *thread_local_obj;
/* in case this thread runs a transaction that aborts,
@@ -218,9 +224,9 @@
/* Push and pop roots from/to the shadow stack. Only allowed inside
transaction. */
-#define STM_PUSH_ROOT(tl, p) (*((tl).shadowstack++) = (object_t *)(p))
-#define STM_POP_ROOT(tl, p) ((p) = (typeof(p))*(--(tl).shadowstack))
-#define STM_POP_ROOT_RET(tl) (*(--(tl).shadowstack))
+#define STM_PUSH_ROOT(tl, p) ((tl).shadowstack++->ss = (object_t *)(p))
+#define STM_POP_ROOT(tl, p) ((p) = (typeof(p))((--(tl).shadowstack)->ss))
+#define STM_POP_ROOT_RET(tl) ((--(tl).shadowstack)->ss)
/* Every thread needs to have a corresponding stm_thread_local_t
diff --git a/c7/test/support.py b/c7/test/support.py
--- a/c7/test/support.py
+++ b/c7/test/support.py
@@ -12,8 +12,12 @@
#define _STM_FAST_ALLOC ...
#define _STM_GCFLAG_WRITE_BARRIER ...
+struct stm_shadowentry_s {
+ object_t *ss;
+};
+
typedef struct {
- object_t **shadowstack, **shadowstack_base;
+ struct stm_shadowentry_s *shadowstack, *shadowstack_base;
object_t *thread_local_obj;
char *mem_clear_on_abort;
size_t mem_bytes_to_clear_on_abort;
@@ -389,7 +393,7 @@
def _allocate_thread_local():
tl = ffi.new("stm_thread_local_t *")
- ss = ffi.new("object_t *[]", SHADOWSTACK_LENGTH)
+ ss = ffi.new("struct stm_shadowentry_s[]", SHADOWSTACK_LENGTH)
_keepalive[tl] = ss
tl.shadowstack = ss
tl.shadowstack_base = ss
@@ -462,7 +466,7 @@
tl = self.tls[self.current_thread]
curlength = tl.shadowstack - tl.shadowstack_base
assert 0 <= curlength < SHADOWSTACK_LENGTH
- tl.shadowstack[0] = ffi.cast("object_t *", o)
+ tl.shadowstack[0].ss = ffi.cast("object_t *", o)
tl.shadowstack += 1
def pop_root(self):
@@ -472,7 +476,7 @@
raise EmptyStack
assert 0 < curlength <= SHADOWSTACK_LENGTH
tl.shadowstack -= 1
- return ffi.cast("object_t *", tl.shadowstack[0])
+ return ffi.cast("object_t *", tl.shadowstack[0].ss)
def push_root_no_gc(self):
"Pushes an invalid object, to crash in case the GC is called"
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