On Wed, Jan 16, 2013 at 3:17 PM, Saul Tamari <stamari@xxxxxxxxx> wrote: > > I'm using a GNU/Linux on an Intel 32bit x86. > > I think that I might be digging too deep. There shouldn't be any > problem with the gs segment or whatever it points to. > > The application is a C program that dynamically loads (using dlopen()) > C++ libraries. > Do I need to set -ftls-model=global-dynamic when compiling the various > C++ libraries so TLS works correctly? Normally that will happen automatically when you use -fPIC. Since you are using 32-bit x86, I guess it is possible that you are compiling code without -fPIC and then putting it in a shared library and then using dlopen. If so, that is your problem; use -fPIC. If you are using -fPIC, then I do not know what is wrong. > Now in order to get eax's value before the call to ___tls_get_attr() I do: > 0xf6f536d9 + 0x3591b = 0xf6f88ff4 > 0xf6f88ff4 - 0x56c = 0xf6f88a88 > > Can this value help me locate which tls value is accessed here? Can I > find it with readelf or objdump? I don't know of any easy way to from that address to the variable being accessed. By looking at the source code for __cxa_get_globals (which is part of GCC, not glibc) I can tell you that the variable in question is a static __thread variable defined in libstdc++-v3/libsupc++/eh_globals.cc. The variabls is used to keep track of all the C++ exceptions currently being thrown. Ian
