On Sun, 7 Mar 2021 12:01:42 +0800 Peter Chen <[email protected]> wrote:
> On 21-03-02 09:56:05, Steven Rostedt wrote: > > On Tue, 2 Mar 2021 16:23:55 +0800 > > Peter Chen <[email protected]> wrote: > > > > s it looks like it uses %pa which IIUC from the printk code, it > > > > >> dereferences the pointer to find it's virtual address. The event has > > > > >> this as the field: > > > > >> > > > > >> __field(struct cdns3_trb *, start_trb_addr) > > > > >> > > > > >> Assigns it with: > > > > >> > > > > >> __entry->start_trb_addr = req->trb; > > > > >> > > > > >> And prints that with %pa, which will dereference pointer at the time > > > > >> of > > > > >> reading, where the address in question may no longer be around. That > > > > >> looks to me as a potential bug. > > > > > > Steven, thanks for reporting. Do you mind sending patch to fix it? > > > If you have no time to do it, I will do it later. > > > > > > > I would have already fixed it, but I wasn't exactly sure how this is used. > > > > In Documentation/core-api/printk-formats.rst we have: > > > > Physical address types phys_addr_t > > ---------------------------------- > > > > :: > > > > %pa[p] 0x01234567 or 0x0123456789abcdef > > > > For printing a phys_addr_t type (and its derivatives, such as > > resource_size_t) which can vary based on build options, regardless of the > > width of the CPU data path. > > > > So it only looks like it is used to for the size of the pointer. > > > > I guess something like this might work: > > > > diff --git a/drivers/usb/cdns3/cdns3-trace.h > > b/drivers/usb/cdns3/cdns3-trace.h > > index 8648c7a7a9dd..d3b8624fc427 100644 > > --- a/drivers/usb/cdns3/cdns3-trace.h > > +++ b/drivers/usb/cdns3/cdns3-trace.h > > @@ -214,7 +214,7 @@ DECLARE_EVENT_CLASS(cdns3_log_request, > > __field(int, no_interrupt) > > __field(int, start_trb) > > __field(int, end_trb) > > - __field(struct cdns3_trb *, start_trb_addr) > > + __field(phys_addr_t, start_trb_addr) > > __field(int, flags) > > __field(unsigned int, stream_id) > > ), > > @@ -230,7 +230,7 @@ DECLARE_EVENT_CLASS(cdns3_log_request, > > __entry->no_interrupt = req->request.no_interrupt; > > __entry->start_trb = req->start_trb; > > __entry->end_trb = req->end_trb; > > - __entry->start_trb_addr = req->trb; > > + __entry->start_trb_addr = *(const phys_addr_t *)req->trb; > > __entry->flags = req->flags; > > __entry->stream_id = req->request.stream_id; > > ), > > @@ -244,7 +244,7 @@ DECLARE_EVENT_CLASS(cdns3_log_request, > > __entry->status, > > __entry->start_trb, > > __entry->end_trb, > > - __entry->start_trb_addr, > > + /* %pa dereferences */ &__entry->start_trb_addr, > > __entry->flags, > > __entry->stream_id > > ) > > > > > > Can you please test it? I don't have the hardware, but I also want to make > > sure I don't break anything. > > > > Thanks, > > > > Since the virtual address for req->trb is NULL before using it. It will > trigger below oops using your change. There is already index > (start_trb/end_trb) for which TRB it has handled, it is not necessary > to trace information for its physical address. I decide to delete this > trace entry, thanks for reporting it. Thanks for fixing / removing it. But I should have added a NULL check before dereferencing, because that's what the vsnprintf() code does. -- Steve
