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>

3 files changed, 159 insertions, 103 deletions

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 80de7003d8c2..5e5b4d33a31c 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -64,6 +64,7 @@ struct perf_counter_attr;
 #include <linux/sem.h>
 #include <asm/siginfo.h>
 #include <asm/signal.h>
+#include <linux/unistd.h>
 #include <linux/quota.h>
 #include <linux/key.h>
 #include <trace/syscall.h>
@@ -112,6 +113,59 @@ struct perf_counter_attr;
 #define __SC_STR_TDECL5(t, a, ...)      #t, __SC_STR_TDECL4(__VA_ARGS__)
 #define __SC_STR_TDECL6(t, a, ...)      #t, __SC_STR_TDECL5(__VA_ARGS__)
 
+
+#define SYSCALL_TRACE_ENTER_EVENT(sname)                                \
+        static struct ftrace_event_call event_enter_##sname;            \
+        static int init_enter_##sname(void)                             \
+        {                                                               \
+                int num;                                                \
+                num = syscall_name_to_nr("sys"#sname);                  \
+                if (num < 0)                                            \
+                        return -ENOSYS;                                 \
+                register_ftrace_event(&event_syscall_enter);            \
+                INIT_LIST_HEAD(&event_enter_##sname.fields);            \
+                init_preds(&event_enter_##sname);                       \
+                return 0;                                               \
+        }                                                               \
+        static struct ftrace_event_call __used                          \
+          __attribute__((__aligned__(4)))                               \
+          __attribute__((section("_ftrace_events")))                    \
+          event_enter_##sname = {                                       \
+                .name                   = "sys_enter"#sname,            \
+                .system                 = "syscalls",                   \
+                .event                  = &event_syscall_enter,         \
+                .raw_init               = init_enter_##sname,           \
+                .regfunc                = reg_event_syscall_enter,      \
+                .unregfunc              = unreg_event_syscall_enter,    \
+                .data                   = "sys"#sname,                  \
+        }
+
+#define SYSCALL_TRACE_EXIT_EVENT(sname)                                 \
+        static struct ftrace_event_call event_exit_##sname;             \
+        static int init_exit_##sname(void)                              \
+        {                                                               \
+                int num;                                                \
+                num = syscall_name_to_nr("sys"#sname);                  \
+                if (num < 0)                                            \
+                        return -ENOSYS;                                 \
+                register_ftrace_event(&event_syscall_exit);             \
+                INIT_LIST_HEAD(&event_exit_##sname.fields);             \
+                init_preds(&event_exit_##sname);                        \
+                return 0;                                               \
+        }                                                               \
+        static struct ftrace_event_call __used                          \
+          __attribute__((__aligned__(4)))                               \
+          __attribute__((section("_ftrace_events")))                    \
+          event_exit_##sname = {                                        \
+                .name                   = "sys_exit"#sname,             \
+                .system                 = "syscalls",                   \
+                .event                  = &event_syscall_exit,          \
+                .raw_init               = init_exit_##sname,            \
+                .regfunc                = reg_event_syscall_exit,       \
+                .unregfunc              = unreg_event_syscall_exit,     \
+                .data                   = "sys"#sname,                  \
+        }
+
 #define SYSCALL_METADATA(sname, nb)                             \
         static const struct syscall_metadata __used             \
           __attribute__((__aligned__(4)))                       \
@@ -121,7 +175,9 @@ struct perf_counter_attr;
                 .nb_args        = nb,                           \
                 .types          = types_##sname,                \
                 .args           = args_##sname,                 \
-        }
+        };                                                      \
+        SYSCALL_TRACE_ENTER_EVENT(sname);                       \
+        SYSCALL_TRACE_EXIT_EVENT(sname);
 
 #define SYSCALL_DEFINE0(sname)                                  \
         static const struct syscall_metadata __used             \
@@ -131,8 +187,9 @@ struct perf_counter_attr;
                 .name           = "sys_"#sname,                 \
                 .nb_args        = 0,                            \
         };                                                      \
+        SYSCALL_TRACE_ENTER_EVENT(_##sname);                    \
+        SYSCALL_TRACE_EXIT_EVENT(_##sname);                     \
         asmlinkage long sys_##sname(void)
-
 #else
 #define SYSCALL_DEFINE0(name)      asmlinkage long sys_##name(void)
 #endif
diff --git a/include/trace/syscall.h b/include/trace/syscall.h
index 3951d774de18..73fb8b4a9955 100644
--- a/include/trace/syscall.h
+++ b/include/trace/syscall.h
@@ -2,6 +2,8 @@
 #define _TRACE_SYSCALL_H
 
 #include <linux/tracepoint.h>
+#include <linux/unistd.h>
+#include <linux/ftrace_event.h>
 
 #include <asm/ptrace.h>
 
@@ -40,15 +42,13 @@ struct syscall_metadata {
 
 #ifdef CONFIG_FTRACE_SYSCALLS
 extern struct syscall_metadata *syscall_nr_to_meta(int nr);
-extern void start_ftrace_syscalls(void);
-extern void stop_ftrace_syscalls(void);
-extern void ftrace_syscall_enter(struct pt_regs *regs);
-extern void ftrace_syscall_exit(struct pt_regs *regs);
-#else
-static inline void start_ftrace_syscalls(void)                  { }
-static inline void stop_ftrace_syscalls(void)                   { }
-static inline void ftrace_syscall_enter(struct pt_regs *regs)   { }
-static inline void ftrace_syscall_exit(struct pt_regs *regs)    { }
+extern int syscall_name_to_nr(char *name);
+extern struct trace_event event_syscall_enter;
+extern struct trace_event event_syscall_exit;
+extern int reg_event_syscall_enter(void *ptr);
+extern void unreg_event_syscall_enter(void *ptr);
+extern int reg_event_syscall_exit(void *ptr);
+extern void unreg_event_syscall_exit(void *ptr);
 #endif
 
 #endif /* _TRACE_SYSCALL_H */
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 08aed439feaf..c7ae25ee95d8 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 @@ print_syscall_exit(struct trace_iterator *iter, int flags)
         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 @@ void ftrace_syscall_enter(struct pt_regs *regs)
         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 @@ void ftrace_syscall_enter(struct pt_regs *regs)
         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 @@ void ftrace_syscall_exit(struct pt_regs *regs)
         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 @@ void ftrace_syscall_exit(struct pt_regs *regs)
         trace_wake_up();
 }
 
-static int init_syscall_tracer(struct trace_array *tr)
+int reg_event_syscall_enter(void *ptr)
 {
-        start_ftrace_syscalls();
-
-        return 0;
+        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_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++;
+        }
+        mutex_unlock(&syscall_trace_lock);
+        return ret;
 }
 
-static void reset_syscall_tracer(struct trace_array *tr)
+void unreg_event_syscall_enter(void *ptr)
 {
-        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,
-};
+        int num;
+        char *name;
 
-static struct tracer syscall_tracer __read_mostly = {
-        .name           = "syscall",
-        .init           = init_syscall_tracer,
-        .reset          = reset_syscall_tracer,
-        .flags          = &syscalls_flags,
-};
+        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);
+}
 
-__init int register_ftrace_syscalls(void)
+int reg_event_syscall_exit(void *ptr)
 {
-        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);
+        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;
+}
 
-        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);
-        }
+void unreg_event_syscall_exit(void *ptr)
+{
+        int num;
+        char *name;
 
-        return register_tracer(&syscall_tracer);
+        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);
 }
-device_initcall(register_ftrace_syscalls);
+
+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
+};