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Peter Anvin" , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Saurabh Singh Sengar , Praveen Kumar , Deepak R Varma Subject: [PATCH v3 3/3] perf/x86/intel: Use sysfs_emit() in show() callback function Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1758917116676189160?= X-GMAIL-MSGID: =?utf-8?q?1758917116676189160?= As per C99 standard, snprintf() returns the number of bytes that would be encoded in the destination buffer when it is sufficiently large. This return value may be different from what the caller is expecting and hence may lead to potential errors in the program. Kernel release 2.6.2 introduced scnprintf() & vscnprintf() which precisely return the actual bytes encoded into the destination buffer. For the sysfs attribute show() callback functions, which returns the number of bytes to the user space, a more recent recommendation is to use sysfs_emit() or sysfs_emit_at() instead of sprintf() family of functions. This is recorded in the Documentation/filesystems/sysfs.rst Kernel documentation file. Issue identified using the coccinelle device_attr_show.cocci script. Signed-off-by: Deepak R Varma --- Changes in v3: - None. Changes in v2: - Revise patch log message to include details on the potential issues with current implementation and how the proposal is a better solution. Feedback provided by Peter Zijlstra arch/x86/events/intel/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index 9fce2d1247a7..75ab89ff3a0f 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -5387,7 +5387,7 @@ 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); } static ssize_t set_sysctl_tfa(struct device *cdev, @@ -5421,7 +5421,7 @@ 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); @@ -5437,7 +5437,7 @@ 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);