On Mon, Nov 08, 2021 at 05:45:42PM -0500, Steven Rostedt wrote:
> On Thu, 4 Nov 2021 10:04:32 -0700
> Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx> wrote:
>
> > Pass iterator through to probes to allow copying data directly to the
> > probe buffers instead of taking multiple copies. Enables eBPF user and
> > raw iterator types out to programs for no-copy scenarios.
> >
> > Signed-off-by: Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx>
> > ---
> > kernel/trace/trace_events_user.c | 97 +++++++++++++++++++++++---------
> > 1 file changed, 69 insertions(+), 28 deletions(-)
> >
> > diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> > index b5fe0550b489..d50118b9630a 100644
> > --- a/kernel/trace/trace_events_user.c
> > +++ b/kernel/trace/trace_events_user.c
> > @@ -39,6 +39,10 @@
> > #define MAX_EVENT_DESC 512
> > #define EVENT_NAME(user_event) ((user_event)->tracepoint.name)
> >
> > +#define MAX_BPF_COPY_SIZE PAGE_SIZE
> > +#define MAX_STACK_BPF_DATA 512
> > +#define copy_nofault copy_from_iter_nocache
> > +
> > static char *register_page_data;
> >
> > static DEFINE_MUTEX(reg_mutex);
> > @@ -63,8 +67,7 @@ struct user_event_refs {
> > struct user_event *events[];
> > };
> >
> > -typedef void (*user_event_func_t) (struct user_event *user,
> > - void *data, u32 datalen,
> > +typedef void (*user_event_func_t) (struct user_event *user, struct iov_iter *i,
> > void *tpdata);
> >
> > static int user_event_parse(char *name, char *args, char *flags,
> > @@ -491,7 +494,7 @@ static struct user_event *find_user_event(char *name, u32 *outkey)
> > /*
> > * Writes the user supplied payload out to a trace file.
> > */
> > -static void user_event_ftrace(struct user_event *user, void *data, u32 datalen,
> > +static void user_event_ftrace(struct user_event *user, struct iov_iter *i,
> > void *tpdata)
> > {
> > struct trace_event_file *file;
> > @@ -506,41 +509,82 @@ static void user_event_ftrace(struct user_event *user, void *data, u32 datalen,
> > return;
> >
> > entry = trace_event_buffer_reserve(&event_buffer, file,
> > - sizeof(*entry) + datalen);
> > + sizeof(*entry) + i->count);
> >
> > if (unlikely(!entry))
> > return;
> >
> > - memcpy(entry + 1, data, datalen);
> > + if (unlikely(!copy_nofault(entry + 1, i->count, i)))
>
> Need:
> __trace_event_discard_commit(event_buffer.buffer, event_buffer.event);
>
> Because the trace_event_buffer_reserve() will not only allocate space on
> the ring buffer, but may also disable preemption.
>
> -- Steve
>
Ah, thank you!
-Beau
>
> > + return;
> >
> > trace_event_buffer_commit(&event_buffer);
> > }
> >
> > #ifdef CONFIG_PERF_EVENTS
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