tracing/ftrace: syscall tracing infrastructure, basics

Provide basic callbacks to do syscall tracing.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <1236401580-5758-2-git-send-email-fweisbec@gmail.com>
[ simplified it to a trace_printk() for now. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace_syscalls.c

@@ -0,0 +1,113 @@
+#include <linux/ftrace.h>
+#include <linux/kernel.h>
+
+#include <asm/syscall.h>
+
+#include "trace_output.h"
+#include "trace.h"
+
+static atomic_t refcount;
+
+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);
+out:
+	atomic_dec(&refcount);
+}
+
+void stop_ftrace_syscalls(void)
+{
+	unsigned long flags;
+	struct task_struct *g, *t;
+
+	if (atomic_dec_return(&refcount))
+		goto out;
+
+	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);
+out:
+	atomic_inc(&refcount);
+}
+
+void ftrace_syscall_enter(struct pt_regs *regs)
+{
+	int syscall_nr;
+
+	syscall_nr = syscall_get_nr(current, regs);
+
+	trace_printk("syscall %d enter\n", syscall_nr);
+}
+
+void ftrace_syscall_exit(struct pt_regs *regs)
+{
+	int syscall_nr;
+
+	syscall_nr = syscall_get_nr(current, regs);
+
+	trace_printk("syscall %d exit\n", syscall_nr);
+}
+
+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,
+};
+
+static struct trace_event syscall_exit_event = {
+	.type		= TRACE_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);