On Sat, 3 Jun 2017 19:42:14 -0300 Breno Leitao <lei...@debian.org> wrote:
> Hi Anton, > > On Sat, Jun 03, 2017 at 08:04:11AM +1000, Anton Blanchard wrote: > > Hi Breno, > > > > > Currently tsk->thread->load_vec and load_fp are not initialized > > > during a task creation, which set garbage to these variables > > > (non-zero value). > > > > Nice catch! It seems like we should zero load_tm too though? > > Yes, it seems we need to zero load_tm also, since it does not seem to > be zeroed anywhere else. > > But I did some tests, and load_tm is always zero after start_thread() > is being called. > > In fact, start_thread() is being called and pt_regs->load_tm is > already zero since the function start. > > I also wrote a SystemTap script[1] to investigate it better, and I've > never seen a single load_tm != 0 in a my machine. I tested on both > POWER8 bare metal and KVM guests. (load_vec and load_fp happened to > have garbage all the time) > > Any idea if this is just occasional event, or, if there is someone > zeroing it in an obscure code? Quite likely no one uses TM :) Try: #include <unistd.h> int main(void) { __builtin_tbegin(0); execlp("/bin/true", "/bin/true", NULL); } Anton