| Message ID | 20130204172259.GA23606@bromo.med.uc.edu |
|---|---|
| State | New |
| Headers | show |
On Feb 4, 2013, at 9:22 AM, Jack Howarth <howarth@bromo.med.uc.edu> wrote: > Currently darwin is unable to utilize libasan with constructors due to the lack of > constructor priority support on that target. > Okay for gcc trunk? Since asan doesn't need cross translation unit priorities, the patch is sufficient to fix all of the semantics needed for asan. I still have a preference, though small, for stable_sort instead of qsort, absent performance data saying qsort is better. Ok. > 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. Since asan doesn't care who goes first, we don't need priorities across translation units for it.
On Feb 4, 2013, at 11:23 AM, Mike Stump <mrs@mrs.kithrup.com> wrote: > On Feb 4, 2013, at 9:22 AM, Jack Howarth <howarth@bromo.med.uc.edu> wrote: >> Currently darwin is unable to utilize libasan with constructors due to the lack of >> constructor priority support on that target. > >> Okay for gcc trunk? > > Since asan doesn't need cross translation unit priorities, the patch is sufficient to fix all of the semantics needed for asan. > > I still have a preference, though small, for stable_sort instead of qsort, absent performance data saying qsort is better. > > Ok. Oh, if you could, could you qsort of the dtors as well. The code exactly mirrors the ctors code.
On Feb 4, 2013, at 11:23 AM, Mike Stump <mrs@mrs.kithrup.com> wrote: > On Feb 4, 2013, at 9:22 AM, Jack Howarth <howarth@bromo.med.uc.edu> wrote: >> Currently darwin is unable to utilize libasan with constructors due to the lack of >> constructor priority support on that target. > >> Okay for gcc trunk? > > Since asan doesn't need cross translation unit priorities, the patch is sufficient to fix all of the semantics needed for asan. > Ok. Committed revision 195735. Note, this doesn't have the test case in it. Please repost just the test case, thanks.
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) {
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 <glider@google.com> Jack Howarth <howarth@bromo.med.uc.edu> Jakub Jelinek <jakub@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 <glider@google.com> Jack Howarth <howarth@bromo.med.uc.edu> Jakub Jelinek <jakub@redhat.com> PR sanitizer/55617 * g++.dg/asan/pr55617.C: New test.