Messages in this thread Patch in this message | | | Date | Wed, 28 Jan 2015 11:26:09 +0000 | From | Javi Merino <> | Subject | Re: [PATCH v4 1/3] tracing: Add array printing helpers |
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On Wed, Jan 28, 2015 at 03:35:57AM +0000, Steven Rostedt wrote: > On Mon, 26 Jan 2015 12:11:49 +0000 > Javi Merino <javi.merino@arm.com> wrote: > > > From: Dave Martin <Dave.Martin@arm.com> > > > > If a trace event contains an array, there is currently no standard > > way to format this for text output. Drivers are currently hacking > > around this by a) local hacks that use the trace_seq functionailty > > directly, or b) just not printing that information. For fixed size > > arrays, formatting of the elements can be open-coded, but this gets > > cumbersome for arrays of non-trivial size. > > > > These approaches result in non-standard content of the event format > > description delivered to userspace, so userland tools needs to be > > taught to understand and parse each array printing method > > individually. > > > > This patch implements common __print_<type>_array() helpers that > > tracepoint implementations can use instead of reinventing them. A > > simple C-style syntax is used to delimit the array and its elements > > {like,this}. > > > > So that the helpers can be used with large static arrays as well as > > dynamic arrays, they take a pointer and element count: they can be > > used with __get_dynamic_array() for use with dynamic arrays. > > > > Cc: Steven Rostedt <rostedt@goodmis.org> > > Cc: Ingo Molnar <mingo@redhat.com> > > Signed-off-by: Dave Martin <Dave.Martin@arm.com> > > Signed-off-by: Javi Merino <javi.merino@arm.com> > > --- > > include/linux/ftrace_event.h | 4 ++++ > > include/trace/ftrace.h | 9 +++++++++ > > kernel/trace/trace_output.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 57 insertions(+) > > > > diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h > > index 0bebb5c348b8..5aa4a9269547 100644 > > --- a/include/linux/ftrace_event.h > > +++ b/include/linux/ftrace_event.h > > @@ -44,6 +44,10 @@ const char *ftrace_print_bitmask_seq(struct trace_seq *p, void *bitmask_ptr, > > const char *ftrace_print_hex_seq(struct trace_seq *p, > > const unsigned char *buf, int len); > > > > +const char *ftrace_print_array_seq(struct trace_seq *p, > > + const void *buf, int buf_len, > > + size_t el_size); > > + > > struct trace_iterator; > > struct trace_event; > > > > diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h > > index 139b5067345b..36afd0ed3458 100644 > > --- a/include/trace/ftrace.h > > +++ b/include/trace/ftrace.h > > @@ -263,6 +263,14 @@ > > #undef __print_hex > > #define __print_hex(buf, buf_len) ftrace_print_hex_seq(p, buf, buf_len) > > > > +#undef __print_array > > +#define __print_array(array, count, el_size) \ > > + ({ \ > > + BUILD_BUG_ON(el_size != 8 && el_size != 16 && \ > > + el_size != 32 && el_size != 64); \ > > I tried testing this patch by writing a print_array myself, and I kept > hitting this BUILD_BUG_ON, and was wondering WTF? Then it dawned on me. > > el_size should not be based on bits, it should be based on bytes. I > passed in "sizeof()" which doesn't work with bits. > > Please update to "el_size < 1 || el_size > 8". > > and adjust the rest accordingly.
Done, I'm testing it now. I'll send a v5 later today.
Cheers, Javi
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