linux-kernel - Re: [PATCH 05/42] arch/x86/events/intel: Convert snprintf to sysfs

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Date: Fri, 19 Jan 2024 14:00:41 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Li Zhijian <lizhijian@...itsu.com>
Cc: linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 05/42] arch/x86/events/intel: Convert snprintf to sysfs_emit

Hello,

On Mon, Jan 15, 2024 at 8:53 PM Li Zhijian <lizhijian@...itsu.com> wrote:
>
> Per filesystems/sysfs.rst, show() should only use sysfs_emit()
> or sysfs_emit_at() when formatting the value to be returned to user space.
>
> coccinelle complains that there are still a couple of functions that use
> snprintf(). Convert them to sysfs_emit().
>
> > ./arch/x86/events/intel/core.c:5496:8-16: WARNING: please use sysfs_emit
> > ./arch/x86/events/intel/core.c:5530:8-16: WARNING: please use sysfs_emit
> > ./arch/x86/events/intel/core.c:5546:8-16: WARNING: please use sysfs_emit
> > ./arch/x86/events/intel/pt.c:99:8-16: WARNING: please use sysfs_emit
>
> No functional change intended
>
> CC: Peter Zijlstra <peterz@...radead.org>
> CC: Ingo Molnar <mingo@...hat.com>
> CC: Arnaldo Carvalho de Melo <acme@...nel.org>
> CC: Mark Rutland <mark.rutland@....com>
> CC: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> CC: Jiri Olsa <jolsa@...nel.org>
> CC: Namhyung Kim <namhyung@...nel.org>
> CC: Ian Rogers <irogers@...gle.com>
> CC: Adrian Hunter <adrian.hunter@...el.com>
> CC: Thomas Gleixner <tglx@...utronix.de>
> CC: Borislav Petkov <bp@...en8.de>
> CC: Dave Hansen <dave.hansen@...ux.intel.com>
> CC: x86@...nel.org
> CC: "H. Peter Anvin" <hpa@...or.com>
> CC: linux-perf-users@...r.kernel.org
> Signed-off-by: Li Zhijian <lizhijian@...itsu.com>
> ---
>  arch/x86/events/intel/core.c | 6 +++---
>  arch/x86/events/intel/pt.c   | 2 +-
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index 0f2786d4e405..aa5fa64a923b 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -5493,7 +5493,7 @@ static ssize_t show_sysctl_tfa(struct device *cdev,
>                               struct device_attribute *attr,
>                               char *buf)
>  {
> -       return snprintf(buf, 40, "%d\n", allow_tsx_force_abort);
> +       return sysfs_emit(buf, "%d\n", allow_tsx_force_abort);

I guess the size doesn't matter here..

Anyway there's freeze_on_smi_show() even uses sprintf().

Thanks,
Namhyung

>  }
>
>  static ssize_t set_sysctl_tfa(struct device *cdev,
> @@ -5527,7 +5527,7 @@ static ssize_t branches_show(struct device *cdev,
>                              struct device_attribute *attr,
>                              char *buf)
>  {
> -       return snprintf(buf, PAGE_SIZE, "%d\n", x86_pmu.lbr_nr);
> +       return sysfs_emit(buf, "%d\n", x86_pmu.lbr_nr);
>  }
>
>  static DEVICE_ATTR_RO(branches);
> @@ -5543,7 +5543,7 @@ static ssize_t pmu_name_show(struct device *cdev,
>                              struct device_attribute *attr,
>                              char *buf)
>  {
> -       return snprintf(buf, PAGE_SIZE, "%s\n", pmu_name_str);
> +       return sysfs_emit(buf, "%s\n", pmu_name_str);
>  }
>
>  static DEVICE_ATTR_RO(pmu_name);
> diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
> index 8e2a12235e62..30bba5f3a840 100644
> --- a/arch/x86/events/intel/pt.c
> +++ b/arch/x86/events/intel/pt.c
> @@ -96,7 +96,7 @@ static ssize_t pt_cap_show(struct device *cdev,
>                 container_of(attr, struct dev_ext_attribute, attr);
>         enum pt_capabilities cap = (long)ea->var;
>
> -       return snprintf(buf, PAGE_SIZE, "%x\n", intel_pt_validate_hw_cap(cap));
> +       return sysfs_emit(buf, "%x\n", intel_pt_validate_hw_cap(cap));
>  }
>
>  static struct attribute_group pt_cap_group __ro_after_init = {
> --
> 2.29.2
>