This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[PATCH] fix PR sanitizer/55617


   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 99 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 == 99.

Attachment: pr55617.diff
Description: Text document


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]