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

[James Clark <james.clark@linaro.org>]

On 12/06/2026 11:56 pm, Aaron Tomlin wrote:
> 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")) {

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@linaro.org>

> +			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)