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 front of the array of constructors on
program
startup. This causes code any instrumented code that executes before the
__asan_init
call to crash.
The attached patch uses a va_gc vector of constructor symbol/priority
records to
queue this data inside machopic_asm_out_constructor. When the ctors vector is
not empty,
the finalize_ctors routine is called in darwin_file_end to sort the queue by
priority,
using a qsort stabilized on original position for identical priority, prior to
emitting
the constructors. 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 (which is similar to what linux shows). 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 The issue of inter module priority support remains unresolved (as it is in
clang/llvm).
The only solution for both compilers is to reorder the linkage of the modules
to insure that the
module with the asan constructor appears first.
/gcc
2013-02-04 Alexander Potapenko <gli...@google.com>
Jack Howarth <howa...@bromo.med.uc.edu>
Jakub Jelinek <ja...@redhat.com>
PR sanitizer/55617
* config/darwin.c (sort_ctor_records): Stabilized qsort
on constructor priority by using original position.
(finalize_ctors): New routine to sort constructors by
priority before use in assemble_integer.
(machopic_asm_out_constructor): Use finalize_ctors if needed.
/gcc/testsuite
2013-02-04 Alexander Potapenko <gli...@google.com>
Jack Howarth <howa...@bromo.med.uc.edu>
Jakub Jelinek <ja...@redhat.com>
PR sanitizer/55617
* g++.dg/asan/pr55617.C: New test.
Index: gcc/config/darwin.c
===================================================================
--- gcc/config/darwin.c (revision 195685)
+++ gcc/config/darwin.c (working copy)
@@ -83,6 +83,14 @@ 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 */
+ int position; /* original position */
+} 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 +1716,48 @@ machopic_select_rtx_section (enum machin
void
machopic_asm_out_constructor (rtx symbol, int priority ATTRIBUTE_UNUSED)
{
+ ctor_record new_elt = {symbol, priority, vec_safe_length (ctors)};
+
+ vec_safe_push (ctors, new_elt);
+
+ if (! MACHOPIC_INDIRECT)
+ fprintf (asm_out_file, ".reference .constructors_used\n");
+}
+
+static int
+sort_ctor_records (const void * a, const void * b)
+{
+ const ctor_record *ca = (const ctor_record *)a;
+ const ctor_record *cb = (const ctor_record *)b;
+ if (ca->priority > cb->priority)
+ return 1;
+ if (ca->priority < cb->priority)
+ return -1;
+ if (ca->position > cb->position)
+ return 1;
+ if (ca->position < cb->position)
+ return -1;
+ return 0;
+}
+
+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");
+ if (vec_safe_length (ctors) > 1)
+ ctors->qsort (sort_ctor_records);
+ 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 +2803,8 @@ 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)
{
