On Wed, Sep 02, 2020 at 11:32:13AM +0200, Miroslav Benes wrote: > Hi, > > it could be a silly question, but better to ask... > > > + if (regs) > > + start_backtrace(&frame, regs->regs[29], regs->pc); > > + else > > + start_backtrace(&frame, thread_saved_fp(task), > > + thread_saved_pc(task)); > > Would this also work for task == current? Given that the original code had > > > - start_backtrace(&frame, > > - (unsigned long)__builtin_frame_address(0), > > - (unsigned long)__save_stack_trace);
Oh whoops; I'm annoyed I didn't spot that. With that gone this cannot work for (task == current && regs == NULL), as we'll erroneously use stale values from the task struct. It looks like the LKDTM tests only trigger cases with non-NULL regs, but IIUC this should show up with show_stack(NULL, NULL, KERN_INFO), as drivers/tty/sysrq.c does for other cpus. Thanks, Mark.
