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Message-ID: <alpine.DEB.2.00.0903090947450.2203@gandalf.stny.rr.com>
Date: Mon, 9 Mar 2009 09:52:20 -0400 (EDT)
From: Steven Rostedt <rostedt@...dmis.org>
To: Frederic Weisbecker <fweisbec@...il.com>
cc: Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
Lai Jiangshan <laijs@...fujitsu.com>,
Peter Zijlstra <peterz@...radead.org>,
Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
Jiaying Zhang <jiayingz@...gle.com>,
Martin Bligh <mbligh@...gle.com>
Subject: Re: [RFC][PATCH 1/2] tracing/ftrace: syscall tracing
infrastructure
On Sat, 7 Mar 2009, Frederic Weisbecker wrote:
> +
> +
> +static atomic_t refcount;
> +
> +enum print_line_t
> +print_syscall_enter(struct trace_iterator *iter, int flags)
> +{
> + struct trace_seq *s = &iter->seq;
> + struct trace_entry *ent = iter->ent;
> + struct syscall_trace_enter *trace;
> + enum syscall_trace_nr syscall;
> + const struct syscall_trace_entry *entry;
> + char *str = NULL;
> + int i, ret;
> +
> + trace_assign_type(trace, ent);
> +
> + syscall = trace->nr;
> +
> + if (!syscall || syscall >= __SYSCALL_TRACE_END)
You still need to print a "\n" otherwise the output of the next line
will start on the current line.
> + return TRACE_TYPE_HANDLED;
> +
> + entry = &syscall_trace_entries[syscall];
> + if (!entry->simple_format) {
> + ret = entry->output.print(trace->args);
> + if (!ret)
> + return TRACE_TYPE_PARTIAL_LINE;
> + return TRACE_TYPE_HANDLED;
> + }
> +
> + ret = trace_seq_printf(s, "syscall %s :", entry->name);
> + if (!ret)
> + return TRACE_TYPE_PARTIAL_LINE;
> +
> + for (i = 0; i < entry->nb_args; i++) {
> + /*
> + * FIXME: the string comes from the user, but on tracing
> + * output time, it may have disappeared from the memory.
> + * May be better to strdup it on tracing time.
> + */
> + if (entry->output.string_mask & (1 << i)) {
> + /* 128 is enough for most path */
> + str = strndup_user((char *)trace->args[i], 128);
> +
> + /* If it faulted badly, the error shoud have been
> + * handled while servicing the syscall, just ignore.
> + */
> + if (str == ERR_PTR(-EFAULT) || str == ERR_PTR(-EINVAL)
> + || str == ERR_PTR(-ENOMEM))
> + return TRACE_TYPE_HANDLED;
> +
> + ret = trace_seq_printf(s, " %s", str);
> + } else {
> + ret = trace_seq_printf(s, " 0x%lx", trace->args[i]);
> + }
> + if (!ret)
> + goto end_partial;
> + }
> + if (!trace_seq_printf(s, "\n"))
> + goto end_partial;
> +
> + kfree(str);
> + return TRACE_TYPE_HANDLED;
> +
> +end_partial:
> + kfree(str);
> + return TRACE_TYPE_PARTIAL_LINE;
> +}
> +
> +enum print_line_t
> +print_syscall_exit(struct trace_iterator *iter, int flags)
> +{
> + struct trace_seq *s = &iter->seq;
> + struct trace_entry *ent = iter->ent;
> + struct syscall_trace_exit *trace;
> + enum syscall_trace_nr syscall;
> + const struct syscall_trace_entry *entry;
> + int ret;
> +
> + trace_assign_type(trace, ent);
> +
> + syscall = trace->nr;
> +
> + if (!syscall || syscall >= __SYSCALL_TRACE_END)
> + return TRACE_TYPE_HANDLED;
> +
> + entry = &syscall_trace_entries[syscall];
> +
> + ret = trace_seq_printf(s, "syscall %s -> 0x%lx\n", entry->name,
> + trace->ret);
> + if (!ret)
> + return TRACE_TYPE_PARTIAL_LINE;
> +
> + return TRACE_TYPE_HANDLED;
> +}
> +
> +void start_ftrace_syscalls(void)
> +{
> + unsigned long flags;
> + struct task_struct *g, *t;
> +
> + if (atomic_inc_return(&refcount) != 1)
> + goto out;
> +
> + read_lock_irqsave(&tasklist_lock, flags);
> +
> + do_each_thread(g, t) {
> + set_tsk_thread_flag(t, TIF_SYSCALL_FTRACE);
> + } while_each_thread(g, t);
> +
> + read_unlock_irqrestore(&tasklist_lock, flags);
> +
> + return;
> +out:
> + atomic_dec(&refcount);
> +}
> +
> +void stop_ftrace_syscalls(void)
> +{
> + unsigned long flags;
> + struct task_struct *g, *t;
> +
> + if (atomic_dec_return(&refcount))
> + return;
> +
> + read_lock_irqsave(&tasklist_lock, flags);
> +
> + do_each_thread(g, t) {
> + clear_tsk_thread_flag(t, TIF_SYSCALL_FTRACE);
> + } while_each_thread(g, t);
> +
> + read_unlock_irqrestore(&tasklist_lock, flags);
> +}
> +
> +void ftrace_syscall_enter(struct pt_regs *regs)
> +{
> + struct trace_array *tr = __get_global_trace();
> + struct syscall_trace_enter *entry;
> + const struct syscall_trace_entry *sys_data;
> + struct ring_buffer_event *event;
> + struct trace_array_cpu *data;
> + int size;
> + int syscall_nr;
> + int nr_offset;
> + int cpu;
> +
> + syscall_nr = syscall_get_nr(current, regs);
> + nr_offset = arch_syscall_trace_nr[syscall_nr];
> + if (!nr_offset || nr_offset >= __SYSCALL_TRACE_END)
> + return;
> +
> + cpu = raw_smp_processor_id();
> + data = tr->data[cpu];
> +
> + if (unlikely(atomic_read(&data->disabled)))
> + return;
> +
> + sys_data = &syscall_trace_entries[nr_offset];
> + size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
> +
> + event = trace_buffer_lock_reserve(tr, TRACE_SYSCALL_ENTER, size, 0, 0);
> + if (!event)
> + return;
> +
> + entry = ring_buffer_event_data(event);
> + entry->nr = nr_offset;
> + syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
> +
> + ring_buffer_unlock_commit(tr->buffer, event);
BTW, you should always use the matching lock. Above you used
trace_buffer_lock_reserve, and here you use ring_buffer_unlock_commit.
This may not work in the future. There is a trace_buffer_unlock_commit
too.
But you are going to change these to trace_current_buffer_lock_reserve and
trace_current_buffer_unlock_commit anyway ;-)
> + trace_wake_up();
> +}
> +
> +void ftrace_syscall_exit(struct pt_regs *regs)
> +{
> + struct trace_array *tr = __get_global_trace();
> + struct syscall_trace_exit *entry;
> + const struct syscall_trace_entry *sys_data;
> + struct ring_buffer_event *event;
> + struct trace_array_cpu *data;
> + int syscall_nr;
> + int nr_offset;
> + int cpu;
> +
> + syscall_nr = syscall_get_nr(current, regs);
> + nr_offset = arch_syscall_trace_nr[syscall_nr];
> + if (!nr_offset || nr_offset >= __SYSCALL_TRACE_END)
> + return;
> +
> + cpu = raw_smp_processor_id();
> + data = tr->data[cpu];
> +
> + if (unlikely(atomic_read(&data->disabled)))
> + return;
> +
> + sys_data = &syscall_trace_entries[nr_offset];
> +
> + event = trace_buffer_lock_reserve(tr, TRACE_SYSCALL_EXIT,
> + sizeof(*entry), 0, 0);
> + if (!event)
> + return;
> +
> + entry = ring_buffer_event_data(event);
> + entry->nr = nr_offset;
> + entry->ret = syscall_get_return_value(current, regs);
> +
> + ring_buffer_unlock_commit(tr->buffer, event);
Same here.
-- Steve
> + trace_wake_up();
> +}
> +
> +static int init_syscall_tracer(struct trace_array *tr)
> +{
> + start_ftrace_syscalls();
> +
> + return 0;
> +}
> +
> +static void reset_syscall_tracer(struct trace_array *tr)
> +{
> + stop_ftrace_syscalls();
> +}
> +
> +static struct trace_event syscall_enter_event = {
> + .type = TRACE_SYSCALL_ENTER,
> + .trace = print_syscall_enter,
> +};
> +
> +static struct trace_event syscall_exit_event = {
> + .type = TRACE_SYSCALL_EXIT,
> + .trace = print_syscall_exit,
> +};
> +
> +static struct tracer syscall_tracer __read_mostly = {
> + .name = "syscall",
> + .init = init_syscall_tracer,
> + .reset = reset_syscall_tracer
> +};
> +
> +__init int register_ftrace_syscalls(void)
> +{
> + int ret;
> +
> + ret = register_ftrace_event(&syscall_enter_event);
> + if (!ret) {
> + printk(KERN_WARNING "event %d failed to register\n",
> + syscall_enter_event.type);
> + WARN_ON_ONCE(1);
> + }
> +
> + ret = register_ftrace_event(&syscall_exit_event);
> + if (!ret) {
> + printk(KERN_WARNING "event %d failed to register\n",
> + syscall_exit_event.type);
> + WARN_ON_ONCE(1);
> + }
> +
> + return register_tracer(&syscall_tracer);
> +}
> +device_initcall(register_ftrace_syscalls);
> --
> 1.6.1
>
>
>
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