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

[Aaron Tomlin]

On Mon, Jun 15, 2026 at 10:32:59AM +0100, James Clark wrote:
> > 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@xxxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxxx/
> > ---
> >   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")) {
> 
> I checked to see if it was possible to include the #define for this constant
> (FIELD_STRING_IP) in the tools folder, but there wasn't anything existing in
> include/ that fits nicely. Either way:
> 
> Reviewed-by: James Clark <james.clark@xxxxxxxxxx>

Hi James,

Yes, unfortunately.

Thank you for the review.

Kind regards,
-- 
Aaron Tomlin

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