On Wed, 23 Mar 2022 at 16:33, <andrey.konovalov@xxxxxxxxx> wrote: > > From: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > > kasan, arm64, scs, stacktrace: collect stack traces from Shadow Call Stack > > Currently, KASAN always uses the normal stack trace collection routines, > which rely on the unwinder, when saving alloc and free stack traces. > > Instead of invoking the unwinder, collect the stack trace by copying > frames from the Shadow Call Stack whenever it is enabled. This reduces > boot time by 30% for all KASAN modes when Shadow Call Stack is enabled. > > Stack staces are collected from the Shadow Call Stack via a new > stack_trace_save_shadow() interface. > > Note that the frame of the interrupted function is not included into > the stack trace, as it is not yet saved on the SCS when an interrupt > happens. > > --- > > To deal with this last thing, we could save the interrupted frame address > in another per-CPU variable. I'll look into implementing this for v3. > > I decided to postpone the changes to stack depot that avoid copying > frames twice until a planned upcoming update for stack depot. That's fair. > Changes v1->v2: > - Provide a kernel-wide stack_trace_save_shadow() interface for collecting > stack traces from shadow stack. > - Use ptrauth_strip_insn_pac() and READ_ONCE_NOCHECK, see the comments. > - Get SCS pointer from x18, as per-task value is meant to save the SCS > value on CPU switches. > - Collect stack frames from SDEI and IRQ contexts. Do any of these new changes introduce new (noticeable) overhead (in particular patch 2)?
