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From: Tao Zhou To: Daniel Bristot de Oliveira Cc: Steven Rostedt , Wim Van Sebroeck , Guenter Roeck , Jonathan Corbet , Ingo Molnar , Thomas Gleixner , Peter Zijlstra , Will Deacon , Catalin Marinas , Marco Elver , Dmitry Vyukov , "Paul E. McKenney" , Shuah Khan , Gabriele Paoloni , Juri Lelli , Clark Williams , Randy Dunlap , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-devel@vger.kernel.org, Tao Zhou Subject: Re: [PATCH V9 01/16] rv: Add Runtime Verification (RV) interface Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Fri, Jul 29, 2022 at 11:38:40AM +0200, Daniel Bristot de Oliveira wrote: > +static int __rv_disable_monitor(struct rv_monitor_def *mdef, bool sync) > +{ > + lockdep_assert_held(&rv_interface_lock); > + > + if (mdef->monitor->enabled) { > + mdef->monitor->enabled = 0; > + mdef->monitor->disable(); If call disable(), the @enabled is set 0 there. > + > + /* > + * Wait for the execution of all events to finish. > + * Otherwise, the data used by the monitor could > + * be inconsistent. i.e., if the monitor is re-enabled. > + */ > + if (sync) > + tracepoint_synchronize_unregister(); > + return 1; Return 0 indicate the actually disabling and successed. > + } > + return 0; If disable a diabled monitor, return error(negative). > +} > + > +/** > + * rv_disable_monitor - disable a given runtime monitor > + * > + * Returns 0 on success. > + */ > +int rv_disable_monitor(struct rv_monitor_def *mdef) > +{ > + __rv_disable_monitor(mdef, true); > + return 0; Always return 0 here, whatever the return value of __rv_disable_monitor(). And this enforce me to look more here, see below. > +} > +static ssize_t enabled_monitors_write(struct file *filp, const char __user *user_buf, > + size_t count, loff_t *ppos) > +{ > + char buff[MAX_RV_MONITOR_NAME_SIZE + 2]; > + struct rv_monitor_def *mdef; > + int retval = -EINVAL; > + bool enable = true; > + char *ptr = buff; > + int len; > + > + if (count < 1 || count > MAX_RV_MONITOR_NAME_SIZE + 1) > + return -EINVAL; > + > + memset(buff, 0, sizeof(buff)); > + > + retval = simple_write_to_buffer(buff, sizeof(buff) - 1, ppos, user_buf, count); > + if (retval < 0) > + return -EFAULT; > + > + ptr = strim(buff); > + > + if (ptr[0] == '!') { > + enable = false; > + ptr++; > + } > + > + len = strlen(ptr); > + if (!len) > + return count; > + > + mutex_lock(&rv_interface_lock); > + > + retval = -EINVAL; > + > + list_for_each_entry(mdef, &rv_monitors_list, list) { > + if (strcmp(ptr, mdef->monitor->name) != 0) > + continue; > + > + /* > + * Monitor found! > + */ > + if (enable) > + retval = rv_enable_monitor(mdef); > + else > + retval = rv_disable_monitor(mdef); About the retval here. If count == 1 and retval == 0, then `retval = count` --> retval == 1. This retval will be returned to user space and dedicate that how many character read and success If retval is 1(it is not possiable, the return value of da_monitor_init_*() called in enable callback in rv_enable_monitor() will be 0, so that return value check is not needed, or any other functions called in enable callback need to check the return value then, so I checked the WARN_ONCE() called in macro rv_attach_trace_probe() which is called in enable callback, if the WARN_ONCE is called, it means that something go wrong. We need to check the return value of WARN_ONCE() in enable callback), the return value will be returned to user space but actually the error(warn) happened. User space do not know. They treat the two kind of return value 1 the same but one is the write count value successed and another is the write error value returned. In enable callback, check rv_attach_trace_probe(): static int enable_wip(void) { int retval = 1; /* * Delete the check of return value of da_monitor_init_wip() * because it is always 0 */ da_monitor_init_wip(); retval &= rv_attach_trace_probe("wip", preempt_enable, handle_preempt_enable); retval &= rv_attach_trace_probe("wip", sched_waking, handle_sched_waking); retval &= rv_attach_trace_probe("wip", preempt_disable, handle_preempt_disable); /* * If the retval is not 0, it mean at least one rv_attach_trace_probe() * is WARN_ONCE(). I am not sure that if the first WARN_ONCE() happened, * then return directly or at here after all rv_attach_trace_probe() is * called and check the retval is 0 or 1. */ if (retval) return -1; return retval; } > + > + if (!retval) > + retval = count; > + > + break; > + } > +/** > + * rv_register_monitor - register a rv monitor. > + * @monitor: The rv_monitor to be registered. > + * > + * Returns 0 if successful, error otherwise. > + */ > +int rv_register_monitor(struct rv_monitor *monitor) > +{ > + struct rv_monitor_def *r; > + int retval = 0; > + > + if (strlen(monitor->name) >= MAX_RV_MONITOR_NAME_SIZE) { s/>=/>/ no? The same check happened in patch 2. Thanks, > + pr_info("Monitor %s has a name longer than %d\n", monitor->name, > + MAX_RV_MONITOR_NAME_SIZE);