On Fri, Dec 18, 2009 at 01:56:50AM +0100, Oleg Nesterov wrote: > Hi. > > do_debug() is obviously wrong wrt PTRACE_SINGLESTEP/TIF_SINGLESTEP, no? > > Afaics this was broken by > > hw-breakpoints: modifying generic debug exception to use > thread-specific debug registers > commit 08d68323d1f0c34452e614263b212ca556dae47f > > To verify, the "patch" below fixes the stepping for me, not sure what > is the proper fix... > > Oleg. > > --- arch/x86/kernel/traps.c~ 2009-12-18 00:20:49.000000000 +0100 > +++ arch/x86/kernel/traps.c 2009-12-18 01:44:05.000000000 +0100 > @@ -575,7 +575,7 @@ dotraplinkage void __kprobes do_debug(st > regs->flags &= ~X86_EFLAGS_TF; > } > si_code = get_si_code(tsk->thread.debugreg6); > - if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS)) > +// if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS)) > send_sigtrap(tsk, regs, error_code, si_code);
But I don't understand why it is broken with the check. If we are in a singlestep exception, dr6 should have its DR_STEP bit set... Single stepping works well for me, after a quick check on gdb. How did you trigger the bug? Thanks.
