tracing: Add trace events for each syscall entry/exit
Layer Frederic's syscall tracer on tracepoints. We create trace events
via hooking into the SYSCALL_DEFINE macros. This allows us to
individually toggle syscall entry and exit points on/off.
Signed-off-by: Jason Baron <jbaron@redhat.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Jiaying Zhang <jiayingz@google.com>
Cc: Martin Bligh <mbligh@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 08aed43..c7ae25e 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -1,15 +1,16 @@
#include <trace/syscall.h>
#include <linux/kernel.h>
+#include <linux/ftrace.h>
#include <asm/syscall.h>
#include "trace_output.h"
#include "trace.h"
-/* Keep a counter of the syscall tracing users */
-static int refcount;
-
-/* Prevent from races on thread flags toggling */
static DEFINE_MUTEX(syscall_trace_lock);
+static int sys_refcount_enter;
+static int sys_refcount_exit;
+static DECLARE_BITMAP(enabled_enter_syscalls, FTRACE_SYSCALL_MAX);
+static DECLARE_BITMAP(enabled_exit_syscalls, FTRACE_SYSCALL_MAX);
/* Option to display the parameters types */
enum {
@@ -95,53 +96,7 @@
return TRACE_TYPE_HANDLED;
}
-void start_ftrace_syscalls(void)
-{
- unsigned long flags;
- struct task_struct *g, *t;
-
- mutex_lock(&syscall_trace_lock);
-
- /* Don't enable the flag on the tasks twice */
- if (++refcount != 1)
- goto unlock;
-
- 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);
-
-unlock:
- mutex_unlock(&syscall_trace_lock);
-}
-
-void stop_ftrace_syscalls(void)
-{
- unsigned long flags;
- struct task_struct *g, *t;
-
- mutex_lock(&syscall_trace_lock);
-
- /* There are perhaps still some users */
- if (--refcount)
- goto unlock;
-
- 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);
-
-unlock:
- mutex_unlock(&syscall_trace_lock);
-}
-
-void ftrace_syscall_enter(struct pt_regs *regs)
+void ftrace_syscall_enter(struct pt_regs *regs, long id)
{
struct syscall_trace_enter *entry;
struct syscall_metadata *sys_data;
@@ -150,6 +105,8 @@
int syscall_nr;
syscall_nr = syscall_get_nr(current, regs);
+ if (!test_bit(syscall_nr, enabled_enter_syscalls))
+ return;
sys_data = syscall_nr_to_meta(syscall_nr);
if (!sys_data)
@@ -170,7 +127,7 @@
trace_wake_up();
}
-void ftrace_syscall_exit(struct pt_regs *regs)
+void ftrace_syscall_exit(struct pt_regs *regs, long ret)
{
struct syscall_trace_exit *entry;
struct syscall_metadata *sys_data;
@@ -178,6 +135,8 @@
int syscall_nr;
syscall_nr = syscall_get_nr(current, regs);
+ if (!test_bit(syscall_nr, enabled_exit_syscalls))
+ return;
sys_data = syscall_nr_to_meta(syscall_nr);
if (!sys_data)
@@ -196,54 +155,94 @@
trace_wake_up();
}
-static int init_syscall_tracer(struct trace_array *tr)
+int reg_event_syscall_enter(void *ptr)
{
- start_ftrace_syscalls();
+ int ret = 0;
+ int num;
+ char *name;
- return 0;
-}
-
-static void reset_syscall_tracer(struct trace_array *tr)
-{
- stop_ftrace_syscalls();
- tracing_reset_online_cpus(tr);
-}
-
-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,
- .flags = &syscalls_flags,
-};
-
-__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);
+ name = (char *)ptr;
+ num = syscall_name_to_nr(name);
+ if (num < 0 || num >= FTRACE_SYSCALL_MAX)
+ return -ENOSYS;
+ mutex_lock(&syscall_trace_lock);
+ if (!sys_refcount_enter)
+ ret = register_trace_syscall_enter(ftrace_syscall_enter);
+ if (ret) {
+ pr_info("event trace: Could not activate"
+ "syscall entry trace point");
+ } else {
+ set_bit(num, enabled_enter_syscalls);
+ sys_refcount_enter++;
}
-
- 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);
+ mutex_unlock(&syscall_trace_lock);
+ return ret;
}
-device_initcall(register_ftrace_syscalls);
+
+void unreg_event_syscall_enter(void *ptr)
+{
+ int num;
+ char *name;
+
+ name = (char *)ptr;
+ num = syscall_name_to_nr(name);
+ if (num < 0 || num >= FTRACE_SYSCALL_MAX)
+ return;
+ mutex_lock(&syscall_trace_lock);
+ sys_refcount_enter--;
+ clear_bit(num, enabled_enter_syscalls);
+ if (!sys_refcount_enter)
+ unregister_trace_syscall_enter(ftrace_syscall_enter);
+ mutex_unlock(&syscall_trace_lock);
+}
+
+int reg_event_syscall_exit(void *ptr)
+{
+ int ret = 0;
+ int num;
+ char *name;
+
+ name = (char *)ptr;
+ num = syscall_name_to_nr(name);
+ if (num < 0 || num >= FTRACE_SYSCALL_MAX)
+ return -ENOSYS;
+ mutex_lock(&syscall_trace_lock);
+ if (!sys_refcount_exit)
+ ret = register_trace_syscall_exit(ftrace_syscall_exit);
+ if (ret) {
+ pr_info("event trace: Could not activate"
+ "syscall exit trace point");
+ } else {
+ set_bit(num, enabled_exit_syscalls);
+ sys_refcount_exit++;
+ }
+ mutex_unlock(&syscall_trace_lock);
+ return ret;
+}
+
+void unreg_event_syscall_exit(void *ptr)
+{
+ int num;
+ char *name;
+
+ name = (char *)ptr;
+ num = syscall_name_to_nr(name);
+ if (num < 0 || num >= FTRACE_SYSCALL_MAX)
+ return;
+ mutex_lock(&syscall_trace_lock);
+ sys_refcount_exit--;
+ clear_bit(num, enabled_exit_syscalls);
+ if (!sys_refcount_exit)
+ unregister_trace_syscall_exit(ftrace_syscall_exit);
+ mutex_unlock(&syscall_trace_lock);
+}
+
+struct trace_event event_syscall_enter = {
+ .trace = print_syscall_enter,
+ .type = TRACE_SYSCALL_ENTER
+};
+
+struct trace_event event_syscall_exit = {
+ .trace = print_syscall_exit,
+ .type = TRACE_SYSCALL_EXIT
+};
