[PATCH v2] perf trace: Fix noise and signed formatting of __probe_ip in bare dynamic probes

[PATCH v2] perf trace: Fix noise and signed formatting of __probe_ip in bare dynamic probes

[Aaron Tomlin]

When a dynamic probe is created without explicitly requested arguments
via perf probe --add, the Ftrace subsystem automatically appends
"__probe_ip" to the tracepoint format to record the instruction pointer.

Currently, perf trace prints this implicit field by default.
Furthermore, because the formatting logic defaults to a standard signed
integer representation, the kernel space memory address is erroneously
displayed as a meaningless negative integer.

    ❯ sudo ./perf trace --event probe:proc_sys_open --max-events 1
         0.000 ps/1316543 probe:proc_sys_open(__probe_ip: -1406056956)

This patch addresses the user experience by combining two refinements:
    1. "__probe_ip" is now hidden from the standard output, as its
       presence adds no contextual value for a bare probe.

    2. If the user explicitly requests verbose output (--verbose),
       "__probe_ip" is intercepted and properly formatted as a hexadecimal
       kernel address, restoring its utility for debugging inline
       function hits.

    ❯ sudo ./perf trace --event probe:proc_sys_open --max-events 1
         0.000 ps/1314074 probe:proc_sys_open()

    ❯ sudo ./perf trace --verbose --event probe:proc_sys_open --max-events 1
    Using CPUID GenuineIntel-6-8E-C
    mmap size 528384B
         0.000 ps/1314366 probe:proc_sys_open(__probe_ip: 0xffffffffac314604)

Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
---
Changes since v1:

 - Fixed a bug where the hardcoded format string for "__probe_ip"
   bypassed the trace->show_arg_names configuration. The formatting
   logic is now properly decoupled to respect trace.show_arg_names when
   verbose mode is enabled.

 - Linked to v1: https://lore.kernel.org/lkml/20260612220843.1320348-1-atomlin@atomlin.com/
---
 tools/perf/builtin-trace.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 48615ddccd93..ac15b5588a27 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -3234,6 +3234,27 @@ static size_t trace__fprintf_tp_fields(struct trace *trace, struct evsel *evsel,
 		if (val == 0 && !trace->show_zeros && !arg->show_zero && arg->strtoul != STUL_BTF_TYPE)
 			continue;
 
+		/*
+		 * __probe_ip is implicitly added to bare dynamic probes.
+		 * Suppress it by default to avoid cluttering the output.
+		 * If verbose mode is enabled, ensure it is formatted as a
+		 * hexadecimal memory address rather than a signed integer.
+		 */
+		if (!strcmp(field->name, "__probe_ip")) {
+			if (!verbose)
+				continue;
+
+			printed += scnprintf(bf + printed, size - printed,
+					     "%s", printed ? ", " : "");
+			if (trace->show_arg_names)
+				printed += scnprintf(bf + printed, size - printed,
+						     "%s: ", field->name);
+
+			printed += scnprintf(bf + printed, size - printed, "%#016llx",
+					     (unsigned long long)val);
+			continue;
+		}
+
 		printed += scnprintf(bf + printed, size - printed, "%s", printed ? ", " : "");
 
 		if (trace->show_arg_names)
-- 
2.51.0