http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55309
--- Comment #35 from Dmitry Vyukov <dvyukov at google dot com> 2013-02-12 08:47:21 UTC --- On Tue, Feb 12, 2013 at 12:39 PM, jakub at gcc dot gnu.org <gcc-bugzi...@gcc.gnu.org> wrote: > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55309 > > --- Comment #34 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-02-12 > 08:39:33 UTC --- > (In reply to comment #32) >> Good news, 0x7fff8000 seems great: >> There is another suggestion (from dvyukov) to use >> -Wl,-Ttext-segment=0x40000000 >> together with zerobase (pie is not required) which is worth investigating. > > Glad to hear that. The disadvantage of > -Wl,-Ttext-segment=0x40000000 is that it requires special command line option > for building the executable, i.e. you can't e.g. just build some shared > library > with -fsanitize=address and leave the main executable non-instrumented. > Plus, I don't see how can > -Wl,-Ttext-segment=0x40000000 be used for x86_64, where you need 16TB of > shadow > memory for >> 3 scale. For zero shadow offset you'd need to place the > executable above 16TB, and that implies non-small model. It is intended for x86_64. The binary is situated at 0x40000000 and it's shadow is at 0x10000000-0x3fffffff (MAP_32BIT can live here as well). Dynamic libraries and mmap live either at 0x7fxxxxxxxxxx or at 0x55xxxxxxxxxx, that is mapped way above the executable. So there are no overlaps. > If -Ttext-segment is meant for 32-bit programs, then it could allow zero > shadow > offset, but with the disadvantage of special building of executables, and on > i?86 the offset already fits into the immediates, so it is basically the > 0x7fff8000 case for x86_64 already. > > (In reply to comment #33) >> > , it might be better to have the scale >> > and offset as arguments of __asan_init? >> >> We did this in the very early version, but it did not work in general. >> Consider you are linking your program with a third-party object >> not built with asan. It may have constructor functions called before main and >> before __asan_init, and those functions call malloc which has to >> call __asan_init, but can not pass arguments. > > I see, but then you could use the global vars (perhaps weak ones in libasan > with some default), combined together with arguments to __asan_init (or some > alternative name of the same function for compatibility). All that it would > do > beyond normal initialization would be complain if the requested scale/offset > pair is different from the chosen one. > > -- > Configure bugmail: http://gcc.gnu.org/bugzilla/userprefs.cgi?tab=email > ------- You are receiving this mail because: ------- > You are on the CC list for the bug.
