From: David Laight <David.Laight@ACULAB.COM>
To: 'Steven Rostedt' <rostedt@goodmis.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Masami Hiramatsu <mhiramat@kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [for-next][PATCH 21/21] tracing: Use a struct alignof to determine trace event field alignment
Date: Mon, 1 Aug 2022 07:46:22 +0000 [thread overview]
Message-ID: <a7d202457150472588df0bd3b7334b3f@AcuMS.aculab.com> (raw)
In-Reply-To: <20220731190435.611455708@goodmis.org>
From: Steven Rostedt
> Sent: 31 July 2022 20:04
>
> alignof() gives an alignment of types as they would be as standalone
> variables. But alignment in structures might be different, and when
> building the fields of events, the alignment must be the actual
> alignment otherwise the field offsets may not match what they actually
> are.
>
> This caused trace-cmd to crash, as libtraceevent did not check if the
> field offset was bigger than the event. The write_msr and read_msr
> events on 32 bit had their fields incorrect, because it had a u64 field
> between two ints. alignof(u64) would give 8, but the u64 field was at a
> 4 byte alignment.
>
> Define a macro as:
>
> ALIGN_STRUCTFIELD(type) ((int)(offsetof(struct {char a; type b;}, b)))
>
> which gives the actual alignment of types in a structure.
The simpler:
__alignof__(struct {type b;})
also works.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-08-01 7:46 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-31 19:03 [for-next][PATCH 00/21] tracing: Updates for 5.20 Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 01/21] USB: mtu3: tracing: Use the new __vstring() helper Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 02/21] batman-adv: " Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 04/21] ftrace/x86: Add back ftrace_expected assignment Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 05/21] rv: Add Runtime Verification (RV) interface Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 06/21] rv: Add runtime reactors interface Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 07/21] rv/include: Add helper functions for deterministic automata Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 08/21] rv/include: Add deterministic automata monitor definition via C macros Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 09/21] rv/include: Add instrumentation helper functions Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 10/21] Documentation/rv: Add a basic documentation Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 11/21] tools/rv: Add dot2c Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 12/21] Documentation/rv: Add deterministic automaton documentation Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 13/21] tools/rv: Add dot2k Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 14/21] Documentation/rv: Add deterministic automata monitor synthesis documentation Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 15/21] Documentation/rv: Add deterministic automata instrumentation documentation Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 16/21] rv/monitor: Add the wip monitor skeleton created by dot2k Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 17/21] rv/monitor: Add the wip monitor Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 18/21] rv/monitor: Add the wwnr monitor Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 19/21] rv/reactor: Add the printk reactor Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 20/21] rv/reactor: Add the panic reactor Steven Rostedt
2022-07-31 19:03 ` [for-next][PATCH 21/21] tracing: Use a struct alignof to determine trace event field alignment Steven Rostedt
2022-08-01 7:46 ` David Laight [this message]
2022-08-01 21:08 ` Steven Rostedt
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