[PATCH v3 2/2] perf trace: Add --bitmask-list command-line option

[Aaron Tomlin <atomlin@atomlin.com>]

Introduce a new '--bitmask-list' command-line option for 'perf trace'.
When this option is specified, the formatting of cpumasks is delegated
to bitmap_scnprintf(), enabling cpumasks to be displayed as a condensed,
human-readable list (e.g., "0,2-5,7") instead of the default hexadecimal
representation. An example is provided below:

❯ sudo ./perf trace --show-cpu --bitmask-list --event ipi:ipi_send_cpumask --max-event 5
     0.000 [000] Xorg/1434 ipi:ipi_send_cpumask(cpumask: 2-3,6, callsite: 0xffffffff9994f8e4, callback: 0xffffffff9994fdd0)
   694.527 [002] chrome/2894 ipi:ipi_send_cpumask(cpumask: 1,3-5, callsite: 0xffffffff9994f8e4, callback: 0xffffffff9994fdd0)
  2666.608 [003] Chrome_ChildIO/2948 ipi:ipi_send_cpumask(cpumask: 4,7, callsite: 0xffffffff9994f8e4, callback: 0xffffffff9994fdd0)
  2673.638 [000] Chrome_IOThrea/2920 ipi:ipi_send_cpumask(cpumask: 2-5, callsite: 0xffffffff9994f8e4, callback: 0xffffffff9994fdd0)
  2714.228 [005] chrome/3375 ipi:ipi_send_cpumask(cpumask: 0-4,6-7, callsite: 0xffffffff9994f8e4, callback: 0xffffffff9994fdd0)

Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
---
 tools/perf/Documentation/perf-trace.txt | 4 ++++
 tools/perf/builtin-trace.c              | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/tools/perf/Documentation/perf-trace.txt b/tools/perf/Documentation/perf-trace.txt
index d0b6c771a1b9..d20b43ea3d37 100644
--- a/tools/perf/Documentation/perf-trace.txt
+++ b/tools/perf/Documentation/perf-trace.txt
@@ -247,6 +247,10 @@ the thread executes on the designated CPUs. Default is to monitor all CPUs.
 	pretty-printing serves as a fallback to hand-crafted pretty printers, as the latter can
 	better pretty-print integer flags and struct pointers.
 
+--bitmask-list::
+	Show bitmasks as a human-readable, condensed list (e.g. "0,2-5,7")
+	instead of the default hexadecimal representation.
+
 --bpf-summary::
 	Collect system call statistics in BPF.  This is only for live mode and
 	works well with -s/--summary option where no argument information is
diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index f8b8431f9543..0142a16830de 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -226,6 +226,7 @@ struct trace {
 	bool			force;
 	bool			vfs_getname;
 	bool			force_btf;
+	bool			bitmask_list;
 	bool			summary_bpf;
 	int			trace_pgfaults;
 	char			*perfconfig_events;
@@ -3279,6 +3280,9 @@ static size_t trace__fprintf_tp_fields(struct trace *trace, struct perf_sample *
 
 			if (syscall_arg.len == 0) {
 				printed += scnprintf(bf + printed, size - printed, "0");
+			} else if (trace->bitmask_list) {
+				printed += bitmap_scnprintf(mask, syscall_arg.len * 8,
+							    bf + printed, size - printed);
 			} else {
 				int i;
 				bool skip_zero = true;
@@ -5589,6 +5593,7 @@ int cmd_trace(int argc, const char **argv)
 		     "start"),
 	OPT_BOOLEAN(0, "force-btf", &trace.force_btf, "Prefer btf_dump general pretty printer"
 		       "to customized ones"),
+	OPT_BOOLEAN(0, "bitmask-list", &trace.bitmask_list, "Show bitmask as a human-readable list"),
 	OPT_BOOLEAN(0, "bpf-summary", &trace.summary_bpf, "Summary syscall stats in BPF"),
 	OPT_INTEGER(0, "max-summary", &trace.max_summary,
 		     "Max number of entries in the summary."),
-- 
2.54.0