Currently darwin is unable to utilize libasan with constructors due to the
lack of
constructor priority support on that target. The asan_finish_file routine
inserts an
essential __asan_init into the array of constructors (via the __mod_init_func
section).
However the insertion occurs at the end, and due to the lack of priority
support for
constructors, these are executed from the start of the array of constructors on
program
startup. This causes code any instrumented code that executes before the
__asan_init
call to crash.
Since darwin sets...
#undef SUPPORTS_INIT_PRIORITY
#define SUPPORTS_INIT_PRIORITY 0
in gcc/config/darwin.h, all constructors are automatically set to
#define DEFAULT_INIT_PRIORITY 65535
in gcc/collect2.c. Any code that attempts to set the constructor/destructor
priority
on darwin results in a compile time error of "constructor priorities are not
supported".
So asan alone should be unique in emitting priorities different from 65535 on
darwin.
The attached patch uses a va_gc vector of constructor symbol/priority records
to queue
this data as it is generated in calls to machopic_asm_out_constructor. Any
instances of
the static constructor with priority MAX_RESERVED_INIT_PRIORITY-1 emitted by
asan are
inserted safely in the front of the vector queue which retains the original
order of the
remaining constructors in the queue. The contents of the vector queue are later
processed
in a new finalize_ctors routine called from darwin_file_end if necessary. The
patch also
adds a g++.dg/asan/pr55617.C test case which is targeted to i?86-*-darwin* and
x86_64-*-darwin*.
The patch reduces the failures observed when running....
make -k check-g++ RUNTESTFLAGS="--target_board=unix'{-fsanitize=address}'"
from 323 to only 85 on darwin (similar to the results on linux). The cov.C
testcase also
fails on gcc trunk with -fsanitize=address when recrafted into a dynamic shared
library
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55617#c28. This patch eliminates
those
crashes. This problem doesn't extend to when the shared library or module is
dlopen'd
(which works in stock gcc trunk and with this patch as well).
The patch has been bootstrap and regression tested on x86_64-apple-darwin12.
Okay for gcc trunk?
Jack
ps Unfortunately the flag_sort variable is unavailable inside of
machopic_asm_out_constructor
so we have to unconditionally test for priority == MAX_RESERVED_INIT_PRIORITY -
1.
/gcc
2013-02-03 Alexander Potapenko <gli...@google.com>
Jack Howarth <howa...@bromo.med.uc.edu>
PR sanitizer/55617
* config/darwin.c (machopic_asm_out_constructor): Use vector to
queue constructors while inserting asan static constructors at front.
(finalize_ctors): New routine to output queued constructors.
(darwin_file_end): Use finalize_ctors.
/gcc/testsuite
2013-02-03 Alexander Potapenko <gli...@google.com>
Jack Howarth <howa...@bromo.med.uc.edu>
PR sanitizer/55617
* g++.dg/asan/pr55617.C: New test.
Index: gcc/config/darwin.c
===================================================================
--- gcc/config/darwin.c (revision 195701)
+++ gcc/config/darwin.c (working copy)
@@ -83,6 +83,13 @@ along with GCC; see the file COPYING3.
kernel) the stubs might still be required, and this will be set true. */
int darwin_emit_branch_islands = false;
+typedef struct GTY(()) ctor_record {
+ rtx symbol;
+ int priority; /* constructor priority */
+} ctor_record;
+
+static GTY(()) vec<ctor_record, va_gc> *ctors = NULL;
+
/* A flag to determine whether we are running c++ or obj-c++. This has to be
settable from non-c-family contexts too (i.e. we can't use the c_dialect_
functions). */
@@ -1708,15 +1715,33 @@ machopic_select_rtx_section (enum machin
void
machopic_asm_out_constructor (rtx symbol, int priority ATTRIBUTE_UNUSED)
{
+ ctor_record new_elt = {symbol, priority};
+ /* Force asan static constructors to front of constructor queue. */
+ if (priority == MAX_RESERVED_INIT_PRIORITY - 1)
+ vec_safe_insert(ctors, 0, new_elt);
+ else
+ vec_safe_push (ctors, new_elt);
+
+ if (! MACHOPIC_INDIRECT)
+ fprintf (asm_out_file, ".reference .constructors_used\n");
+}
+
+static void
+finalize_ctors()
+{
+ unsigned int i;
+ ctor_record *elt;
+
if (MACHOPIC_INDIRECT)
switch_to_section (darwin_sections[mod_init_section]);
else
switch_to_section (darwin_sections[constructor_section]);
- assemble_align (POINTER_SIZE);
- assemble_integer (symbol, POINTER_SIZE / BITS_PER_UNIT, POINTER_SIZE, 1);
- if (! MACHOPIC_INDIRECT)
- fprintf (asm_out_file, ".reference .constructors_used\n");
+ FOR_EACH_VEC_SAFE_ELT (ctors, i, elt)
+ {
+ assemble_align (POINTER_SIZE);
+ assemble_integer (elt->symbol, POINTER_SIZE / BITS_PER_UNIT,
POINTER_SIZE, 1);
+ }
}
void
@@ -2762,6 +2787,8 @@ darwin_file_start (void)
void
darwin_file_end (void)
{
+ if (!vec_safe_is_empty (ctors))
+ finalize_ctors();
machopic_finish (asm_out_file);
if (strcmp (lang_hooks.name, "GNU C++") == 0)
{
--- /dev/null 2013-02-02 10:53:51.000000000 -0500
+++ gcc/testsuite/g++.dg/asan/pr55617.C 2013-02-02 10:22:17.000000000 -0500
@@ -0,0 +1,8 @@
+// { dg-do run { target { i?86-*-darwin* x86_64-*-darwin* } } }
+
+struct c18 {
+ virtual void bar() { }
+};
+c18 ret;
+int main () {
+}
