From: Kees Cook <keescook@chromium.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Next Mailing List <linux-next@vger.kernel.org>
Subject: Re: linux-next: build failure after merge of the kspp tree
Date: Tue, 25 Jan 2022 14:07:14 -0800 [thread overview]
Message-ID: <202201251402.0FB08DB@keescook> (raw)
In-Reply-To: <20220125162859.2b3cc8a0@gandalf.local.home>
On Tue, Jan 25, 2022 at 04:28:59PM -0500, Steven Rostedt wrote:
> On Tue, 25 Jan 2022 16:23:26 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > > > #undef __get_rel_dynamic_array
> > > > -#define __get_rel_dynamic_array(field) \
> > > > - ((void *)(&__entry->__rel_loc_##field) + \
> > > > - sizeof(__entry->__rel_loc_##field) + \
> > > > +#define __get_rel_dynamic_array(field) \
> > > > + ((void *)__entry + \
> > > > + offsetof(typeof(*__entry), __rel_loc_##field) + \
> > > > + sizeof(__entry->__rel_loc_##field) + \
> > > > (__entry->__rel_loc_##field & 0xffff))
> > > >
> > > > #undef __get_rel_dynamic_array_len
> > >
>
> I also do not like the the inconsistency between
> sizeof(__entry->__rel_loc_##field) and sizeof(u32) that is used in the
> calculation part:
>
>
> #define __rel_dynamic_array(type, item, len) \
> __item_length = (len) * sizeof(type); \
> __data_offsets->item = __data_size + \
> offsetof(typeof(*entry), __data) - \
> offsetof(typeof(*entry), __rel_loc_##item) - \
> sizeof(u32); \
> __data_offsets->item |= __item_length << 16; \
> __data_size += __item_length;
>
> Why is one using sizeof(u32) and the other using the size of the field?
It might make more sense to calculate everything as an offset within
__data[] instead of from the start of __entry. The patch I sent just did
in perf.h exactly what Masami did in trace_event.h. That worked. I had
an earlier version that did this horrible thing which could probably be
significantly improved, since I just subtract the offset of __data:
#undef __get_rel_dynamic_array
#define __get_rel_dynamic_array(field) \
- ((void *)(&__entry->__rel_loc_##field) + \
- sizeof(__entry->__rel_loc_##field) + \
- (__entry->__rel_loc_##field & 0xffff))
+ ((void *)&__entry->__data[ \
+ offsetof(typeof(*__entry), __rel_loc_##field) \
+ + sizeof(__entry->__rel_loc_##field) \
+ + (__entry->__rel_loc_##field & 0xffff) \
+ - offsetof(typeof(*__entry), __data) \
+ ])
> Just to let you know what is happening. As dynamic elements of the trace
> event needs to be appended at the end of the event, the above macros are
> defined and then run through the TRACE_EVENT() macro, where the
> TP_STRUCT__entry() is parsed to calculate where each item will be for that
> event.
>
> static inline notrace int trace_event_get_offsets_##call( \
> struct trace_event_data_offsets_##call *__data_offsets, proto) \
> { \
> int __data_size = 0; \
> int __maybe_unused __item_length; \
> struct trace_event_raw_##call __maybe_unused *entry; \
> \
> tstruct; \
> \
> return __data_size; \
> }
>
>
> The tstruct is the TP_STRUCT__entry() and for each __rel_dynamic_array() or
> __dynamic_array(), the __data_size gets updated and saved into the
> __data_offsets that holds where each item is.
>
> The rel versions sets the offset from its location to the data, where as
> the non rel versions sets the offset from the beginning of the event to the
> data.
Could this just be
#define __get_rel_dynamic_array(field) \
((void *)(&__entry->data[__entry->__rel_loc_##field & 0xffff])
?
--
Kees Cook
next prev parent reply other threads:[~2022-01-25 22:07 UTC|newest]
Thread overview: 108+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-25 3:50 linux-next: build failure after merge of the kspp tree Stephen Rothwell
2022-01-25 7:44 ` Kees Cook
2022-01-25 13:27 ` Masami Hiramatsu
2022-01-25 14:01 ` Steven Rostedt
2022-01-25 17:53 ` Kees Cook
2022-01-25 14:31 ` Masami Hiramatsu
2022-01-25 15:49 ` Steven Rostedt
2022-01-25 17:54 ` Kees Cook
2022-01-25 18:41 ` Steven Rostedt
2022-01-25 20:57 ` Kees Cook
2022-01-25 21:23 ` Steven Rostedt
2022-01-25 21:28 ` Steven Rostedt
2022-01-25 22:07 ` Kees Cook [this message]
2022-01-25 22:21 ` Steven Rostedt
2022-01-26 0:35 ` Masami Hiramatsu
2022-01-26 1:16 ` Steven Rostedt
2022-01-26 3:18 ` Kees Cook
2022-01-26 3:26 ` Steven Rostedt
2022-01-26 19:41 ` Beau Belgrave
2022-01-26 21:00 ` Steven Rostedt
2022-01-26 3:52 ` Masami Hiramatsu
2022-01-26 4:06 ` Steven Rostedt
2022-01-26 3:17 ` Kees Cook
2022-01-25 22:01 ` Kees Cook
-- strict thread matches above, loose matches on Subject: below --
2024-03-05 3:50 Stephen Rothwell
2024-03-05 9:54 ` Kees Cook
2023-09-14 1:50 Stephen Rothwell
2023-09-14 3:07 ` Kees Cook
2023-01-05 2:25 Stephen Rothwell
2023-01-05 3:22 ` Kees Cook
2023-01-05 4:24 ` Stephen Rothwell
2022-12-01 3:07 Stephen Rothwell
2022-12-01 16:31 ` Kees Cook
2022-07-28 10:55 Stephen Rothwell
2022-07-28 15:12 ` Matthias Kaehlcke
2022-05-05 7:40 Stephen Rothwell
2022-05-07 17:18 ` Kees Cook
2022-03-16 7:32 Stephen Rothwell
2022-03-17 1:01 ` Linus Walleij
2022-03-17 8:24 ` Marc Zyngier
2022-03-09 10:10 Stephen Rothwell
2022-03-09 16:52 ` Kees Cook
2022-03-09 16:58 ` Hans de Goede
2022-03-09 17:18 ` Kees Cook
2022-02-28 22:27 Stephen Rothwell
2022-02-28 23:02 ` Kees Cook
2022-03-02 9:16 ` Stephen Rothwell
2022-03-03 7:29 ` Stephen Rothwell
2022-01-30 23:09 Stephen Rothwell
2022-01-31 4:04 ` Kees Cook
2022-01-31 4:59 ` Stephen Rothwell
2022-01-31 6:19 ` Kees Cook
2022-01-31 19:10 ` Saeed Mahameed
2022-01-31 21:06 ` Kees Cook
2022-01-30 22:34 Stephen Rothwell
2022-01-30 23:24 ` Herbert Xu
2022-01-31 0:15 ` Stephen Rothwell
2022-01-31 0:20 ` Herbert Xu
2022-01-31 0:41 ` Stephen Rothwell
2022-01-25 3:24 Stephen Rothwell
2022-01-25 3:43 ` Kees Cook
2022-02-08 4:42 ` Stephen Rothwell
2022-02-08 6:13 ` Kees Cook
2022-01-25 2:55 Stephen Rothwell
2022-01-25 3:02 ` Stephen Rothwell
2022-01-25 3:22 ` Kees Cook
2022-01-25 0:57 Stephen Rothwell
2022-01-25 3:35 ` Kees Cook
2022-01-25 14:07 ` David Sterba
2021-09-16 3:34 Stephen Rothwell
2021-09-16 6:00 ` Kees Cook
2021-08-26 7:52 Stephen Rothwell
2021-08-26 15:38 ` Kees Cook
2020-06-23 3:51 Stephen Rothwell
2020-06-23 3:56 ` David Miller
2020-06-21 13:48 Stephen Rothwell
2020-06-21 15:36 ` Kees Cook
2018-07-27 9:02 Stephen Rothwell
2018-07-27 9:06 ` Stephen Rothwell
2018-07-27 10:55 ` Stephen Rothwell
2018-07-27 12:55 ` Will Deacon
2018-07-27 13:01 ` Will Deacon
2018-07-27 13:27 ` Will Deacon
2018-07-27 16:00 ` Kees Cook
2018-07-30 7:33 ` Stephen Rothwell
2018-07-30 14:47 ` Laura Abbott
2018-07-30 16:37 ` Will Deacon
2018-07-31 10:09 ` Will Deacon
2018-07-31 11:27 ` Stephen Rothwell
2017-11-08 5:23 Stephen Rothwell
2017-11-08 23:43 ` Kees Cook
2017-11-09 0:18 ` Darrick J. Wong
2017-11-09 0:31 ` Kees Cook
2017-06-20 4:56 Stephen Rothwell
2017-06-20 5:39 ` Kees Cook
2017-06-20 5:42 ` John Johansen
2017-06-20 5:39 ` John Johansen
2017-06-26 18:19 ` Kees Cook
2017-06-27 3:33 ` James Morris
2017-06-27 22:16 ` Kees Cook
2017-06-28 5:48 ` James Morris
2017-06-16 1:30 Stephen Rothwell
2017-06-16 2:51 ` Daniel Micay
2017-06-16 2:52 ` Daniel Micay
2017-06-16 3:20 ` Kees Cook
2017-06-16 3:31 ` Stephen Rothwell
2017-06-19 0:23 ` Stephen Rothwell
2017-06-19 21:01 ` Kees Cook
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