On Mon, Jun 28, 2021 at 11:53:41AM +0530, Kajol Jain wrote: > Commit 48a1f565261d ("perf script python: Add more PMU fields > to event handler dict") added functionality to report fields like > weight, iregs, uregs etc via perf report. > That commit predefined buffer size to 512 bytes to print those fields. > > But incase of powerpc, since we added extended regs support > in commits: > > Commit 068aeea3773a ("perf powerpc: Support exposing Performance Monitor > Counter SPRs as part of extended regs") > Commit d735599a069f ("powerpc/perf: Add extended regs support for > power10 platform") > > Now iregs can carry more bytes of data and this predefined buffer size > can result to data loss in perf script output. > > Patch resolve this issue by making buffer size dynamic based on number > of registers needed to print. It also changed return type for function > "regs_map" from int to void, as the return value is not being used by > the caller function "set_regs_in_dict". > > Fixes: 068aeea3773a ("perf powerpc: Support exposing Performance Monitor > Counter SPRs as part of extended regs") > Signed-off-by: Kajol Jain <kj...@linux.ibm.com> > --- > .../util/scripting-engines/trace-event-python.c | 17 ++++++++++++----- > 1 file changed, 12 insertions(+), 5 deletions(-) > > diff --git a/tools/perf/util/scripting-engines/trace-event-python.c > b/tools/perf/util/scripting-engines/trace-event-python.c > index 4e4aa4c97ac5..c8c9706b4643 100644 > --- a/tools/perf/util/scripting-engines/trace-event-python.c > +++ b/tools/perf/util/scripting-engines/trace-event-python.c [...] > @@ -713,7 +711,16 @@ static void set_regs_in_dict(PyObject *dict, > struct evsel *evsel) > { > struct perf_event_attr *attr = &evsel->core.attr; > - char bf[512]; > + > + /* > + * Here value 28 is a constant size which can be used to print > + * one register value and its corresponds to: > + * 16 chars is to specify 64 bit register in hexadecimal. > + * 2 chars is for appending "0x" to the hexadecimal value and > + * 10 chars is for register name. > + */ > + int size = __sw_hweight64(attr->sample_regs_intr) * 28; > + char bf[size];
I propose using a template rather than a magic number here. Something like: const char reg_name_tmpl[] = "10 chars "; const char reg_value_tmpl[] = "0x0123456789abcdef"; const int size = __sw_hweight64(attr->sample_regs_intr) + sizeof reg_name_tmpl + sizeof reg_value_tmpl; Pardon my ignorance, but is there no separation/whitespace between the name and the value? And is there some significance to 10 characters for the register name, or is that a magic number? PC