On Mon, Jan 09, 2017 at 03:58:04PM +0100, Martin Liška wrote:
> >> Well, having following sample:
> >>
> >> int
> >> main (int argc, char **argv)
> >> {
> >> int *ptr = 0;
> >>
> >> {
> >> int a;
> >> ptr = &a;
> >> *ptr = 12345;
> >> }
> >>
> >> *ptr = 12345;
> >> return *ptr;
> >> }
> >>
> I'm still not sure how to do that. Problem is that transformation from:
>
> ASAN_MARK (UNPOISON, &a, 4);
> a = 5;
> ASAN_MARK (POISON, &a, 4);
>
> to
>
> a_8 = 5;
> a_9 = ASAN_POISON ();
>
> happens in tree-ssa.c, after SSA is created, in situation where we prove the
> 'a'
> does not need to live in memory. Thus said, question is how to identify that
> we
> need to transform into SSA in a different way:
>
> a_10 = ASAN_POISON ();
> ASAN_POISON (a_10);
I meant something like this (completely untested, and without the testcase
added to the testsuite).
The incremental patch as is relies on the ASAN_POISON_USE call having the
argument the result of ASAN_POISON, it would ICE if that is not the case
(especially if -fsanitize-recover=address). Dunno if some optimization
might decide to create a PHI in between, say merge two unrelated vars for
if (something)
{
x_1 = ASAN_POISON ();
...
ASAN_POISON_USE (x_1);
}
else
{
y_2 = ASAN_POISON ();
...
ASAN_POISON_USE (y_2);
}
to turn that into:
if (something)
x_1 = ASAN_POISON ();
else
y_2 = ASAN_POISON ();
_3 = PHI <x_1, y_2>;
...
ASAN_POISON_USE (_3);
If it did, we would ICE because ASAN_POISON_USE would survive this way until
expansion. A quick fix for the ICE (if it can ever happen) would be easy,
in sanopt remove ASAN_POISON_USE calls which have argument that is not lhs
of ASAN_POISON (all other ASAN_POISON_USE calls will be handled by my
incremental patch). Of course that would also mean in that case we'd report
a read rather than write. But if it can't happen or is very unlikely to
happen, then it is a non-issue.
Something missing from the patch is some change in DCE to remove ASAN_POISON
calls without lhs earlier. I think we can't make ASAN_POISON ECF_CONST, we
don't want it to be merged for different variables.
--- gcc/internal-fn.def.jj 2017-01-16 13:19:49.000000000 +0100
+++ gcc/internal-fn.def 2017-01-16 14:25:37.427962196 +0100
@@ -167,6 +167,7 @@ DEF_INTERNAL_FN (ABNORMAL_DISPATCHER, EC
DEF_INTERNAL_FN (ASAN_CHECK, ECF_TM_PURE | ECF_LEAF | ECF_NOTHROW, ".R...")
DEF_INTERNAL_FN (ASAN_MARK, ECF_LEAF | ECF_NOTHROW, ".R..")
DEF_INTERNAL_FN (ASAN_POISON, ECF_LEAF | ECF_NOTHROW | ECF_NOVOPS, NULL)
+DEF_INTERNAL_FN (ASAN_POISON_USE, ECF_LEAF | ECF_NOTHROW | ECF_NOVOPS, NULL)
DEF_INTERNAL_FN (ADD_OVERFLOW, ECF_CONST | ECF_LEAF | ECF_NOTHROW, NULL)
DEF_INTERNAL_FN (SUB_OVERFLOW, ECF_CONST | ECF_LEAF | ECF_NOTHROW, NULL)
DEF_INTERNAL_FN (MUL_OVERFLOW, ECF_CONST | ECF_LEAF | ECF_NOTHROW, NULL)
--- gcc/asan.c.jj 2017-01-16 13:19:49.000000000 +0100
+++ gcc/asan.c 2017-01-16 14:52:34.022044223 +0100
@@ -3094,6 +3094,8 @@ create_asan_shadow_var (tree var_decl,
return *slot;
}
+/* Expand ASAN_POISON ifn. */
+
bool
asan_expand_poison_ifn (gimple_stmt_iterator *iter,
bool *need_commit_edge_insert,
@@ -3107,8 +3109,8 @@ asan_expand_poison_ifn (gimple_stmt_iter
return true;
}
- tree shadow_var = create_asan_shadow_var (SSA_NAME_VAR (poisoned_var),
- shadow_vars_mapping);
+ tree shadow_var = create_asan_shadow_var (SSA_NAME_VAR (poisoned_var),
+ shadow_vars_mapping);
bool recover_p;
if (flag_sanitize & SANITIZE_USER_ADDRESS)
@@ -3122,16 +3124,16 @@ asan_expand_poison_ifn (gimple_stmt_iter
ASAN_MARK_POISON),
build_fold_addr_expr (shadow_var), size);
- use_operand_p use_p;
+ gimple *use;
imm_use_iterator imm_iter;
- FOR_EACH_IMM_USE_FAST (use_p, imm_iter, poisoned_var)
+ FOR_EACH_IMM_USE_STMT (use, imm_iter, poisoned_var)
{
- gimple *use = USE_STMT (use_p);
if (is_gimple_debug (use))
continue;
int nargs;
- tree fun = report_error_func (false, recover_p, tree_to_uhwi (size),
+ bool store_p = gimple_call_internal_p (use, IFN_ASAN_POISON_USE);
+ tree fun = report_error_func (store_p, recover_p, tree_to_uhwi (size),
&nargs);
gcall *call = gimple_build_call (fun, 1,
@@ -3160,7 +3162,10 @@ asan_expand_poison_ifn (gimple_stmt_iter
else
{
gimple_stmt_iterator gsi = gsi_for_stmt (use);
- gsi_insert_before (&gsi, call, GSI_NEW_STMT);
+ if (store_p)
+ gsi_replace (&gsi, call, true);
+ else
+ gsi_insert_before (&gsi, call, GSI_NEW_STMT);
}
}
--- gcc/tree-into-ssa.c.jj 2017-01-01 12:45:35.000000000 +0100
+++ gcc/tree-into-ssa.c 2017-01-16 14:32:14.853808726 +0100
@@ -38,6 +38,7 @@ along with GCC; see the file COPYING3.
#include "tree-ssa.h"
#include "domwalk.h"
#include "statistics.h"
+#include "asan.h"
#define PERCENT(x,y) ((float)(x) * 100.0 / (float)(y))
@@ -1807,6 +1808,26 @@ maybe_replace_use_in_debug_stmt (use_ope
}
+/* If DEF has x_5 = ASAN_POISON () as its current def, add
+ ASAN_POISON_USE (x_5) stmt before GSI to denote the stmt writes into
+ a poisoned (out of scope) variable. */
+
+static void
+maybe_add_asan_poison_write (tree def, gimple_stmt_iterator *gsi)
+{
+ tree cdef = get_current_def (def);
+ if (cdef != NULL
+ && TREE_CODE (cdef) == SSA_NAME
+ && gimple_call_internal_p (SSA_NAME_DEF_STMT (cdef), IFN_ASAN_POISON))
+ {
+ gcall *call
+ = gimple_build_call_internal (IFN_ASAN_POISON_USE, 1, cdef);
+ gimple_set_location (call, gimple_location (gsi_stmt (*gsi)));
+ gsi_insert_before (gsi, call, GSI_SAME_STMT);
+ }
+}
+
+
/* If the operand pointed to by DEF_P is an SSA name in NEW_SSA_NAMES
or OLD_SSA_NAMES, or if it is a symbol marked for renaming,
register it as the current definition for the names replaced by
@@ -1837,7 +1858,11 @@ maybe_register_def (def_operand_p def_p,
def = get_or_create_ssa_default_def (cfun, sym);
}
else
- def = make_ssa_name (def, stmt);
+ {
+ if (asan_sanitize_use_after_scope ())
+ maybe_add_asan_poison_write (def, &gsi);
+ def = make_ssa_name (def, stmt);
+ }
SET_DEF (def_p, def);
tree tracked_var = target_for_debug_bind (sym);
--- gcc/internal-fn.c.jj 2017-01-16 13:19:49.000000000 +0100
+++ gcc/internal-fn.c 2017-01-16 14:26:10.828529039 +0100
@@ -388,6 +388,14 @@ expand_ASAN_POISON (internal_fn, gcall *
gcc_unreachable ();
}
+/* This should get expanded in the sanopt pass. */
+
+static void
+expand_ASAN_POISON_USE (internal_fn, gcall *)
+{
+ gcc_unreachable ();
+}
+
/* This should get expanded in the tsan pass. */
static void
Jakub
