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Message-ID: <20231130192554.10da680c@gandalf.local.home> Date: Thu, 30 Nov 2023 19:25:54 -0500 From: Steven Rostedt <rostedt@...dmis.org> To: Łukasz Bartosik <lb@...ihalf.com> Cc: Jason Baron <jbaron@...mai.com>, Jim Cromie <jim.cromie@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, Douglas Anderson <dianders@...omium.org>, Guenter Roeck <groeck@...gle.com>, Yaniv Tzoreff <yanivt@...gle.com>, Benson Leung <bleung@...gle.com>, Vincent Whitchurch <vincent.whitchurch@...s.com>, Pekka Paalanen <ppaalanen@...il.com>, Sean Paul <seanpaul@...omium.org>, Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org, upstream@...ihalf.com, pmladek@...e.com, sergey.senozhatsky@...il.com, john.ogness@...utronix.de, Simon Ser <contact@...rsion.fr> Subject: Re: [PATCH v2 05/15] tracefs: add __get_str_strip_nl - RFC On Fri, 1 Dec 2023 00:40:38 +0100 Łukasz Bartosik <lb@...ihalf.com> wrote: > From: Jim Cromie <jim.cromie@...il.com> > > This variant of __get_str() removes the trailing newline. It is for > use by printk/debug-ish events which already have a trailing newline. > It is here to support: > > https://lore.kernel.org/lkml/ > 20200825153338.17061-1-vincent.whitchurch@...s.com/ Line wrap breakage. > which taught dyndbg to send pr_debug() msgs to tracefs, via -x/T flag. > > It "reused" the include/trace/events/printk.h console event, > which does the following: > > TP_fast_assign( > /* > * Each trace entry is printed in a new line. > * If the msg finishes with '\n', cut it off > * to avoid blank lines in the trace. > */ > if (len > 0 && (msg[len-1] == '\n')) > len -= 1; > > memcpy(__get_str(s), msg, len); > __get_str(s)[len] = 0; > ), > > That trim work could be avoided, *if* all pr_debug() callers are > known to have no '\n' to strip. While that's not true for *all* > callsites, it is 99+% true for DRM.debug callsites, and can be made > true for some subsets of prdbg/dyndbg callsites. > > WANTED: macros to validate that a literal format-str has or doesn't > have a trailing newline, or to provide or trim trailing newline(s?). > Should be usable in TP_printk* defns, for use in new event defns. > > Cc: <rostedt@...dmis.org> > Cc: Vincent Whitchurch <vincent.whitchurch@...s.com> > Cc: <daniel@...ll.ch> > Cc: <pmladek@...e.com> > Cc: <sergey.senozhatsky@...il.com> > Cc: <john.ogness@...utronix.de> > Cc: Simon Ser <contact@...rsion.fr> > Cc: Sean Paul <seanpaul@...omium.org> > Signed-off-by: Jim Cromie <jim.cromie@...il.com> > Signed-off-by: Łukasz Bartosik <lb@...ihalf.com> > --- > include/trace/stages/stage3_trace_output.h | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/include/trace/stages/stage3_trace_output.h b/include/trace/stages/stage3_trace_output.h > index c1fb1355d309..92a79bd5c0cd 100644 > --- a/include/trace/stages/stage3_trace_output.h > +++ b/include/trace/stages/stage3_trace_output.h > @@ -19,6 +19,15 @@ > #undef __get_str > #define __get_str(field) ((char *)__get_dynamic_array(field)) > > +#undef __get_str_strip_nl > +#define __get_str_strip_nl(field) \ > + ({ \ > + char *s = __get_str(field); \ > + size_t len = strlen(s); \ > + if (len && s[len-1] == '\n') \ > + s[len-1] = '\0'; s; \ > + }) I'd be worried about modifying the string itself as you are doing above. That's modifying the source which may have unintended consequences. That said, there's a trace_seq that is available for stage 3 called "p". You can use that: #define __get_str_strip_nl(field) \ ({ \ char *s = trace_seq_buffer_ptr(p); \ size_t len; \ trace_seq_printf(p, "%s", __get_str(field)); \ trace_seq_putc(p, '\0'); \ len = strlen(s); \ if (len && s[len-1] == '\n') \ s[len-1] = '\0'; \ s; \ }) -- Steve > + > #undef __get_rel_dynamic_array > #define __get_rel_dynamic_array(field) \ > ((void *)__entry + \
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