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Subject[PATCH 7/7] V2 add syscall tracepoints
Layer Frederic's syscall tracer on tracepoints. We create trace events via
hooking into the SYCALL_DEFINE macros. This allows us to individually toggle
syscall entry and exit points on/off.


Signed-off-by: Jason Baron <jbaron@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>

---
include/linux/syscalls.h | 75 +++++++++++++++++-
include/trace/syscall.h | 18 ++--
kernel/trace/trace_syscalls.c | 171 +++++++++++++++++++---------------------
3 files changed, 163 insertions(+), 101 deletions(-)
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index fa4242c..766502e 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 +113,73 @@ 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 int reg_enter_##sname(void) \
+ { \
+ return reg_event_syscall_enter("sys"#sname); \
+ } \
+ static void unreg_enter_##sname(void) \
+ { \
+ unreg_event_syscall_enter("sys"#sname); \
+ } \
+ 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_enter_##sname, \
+ .unregfunc = unreg_enter_##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 int reg_exit_##sname(void) \
+ { \
+ return reg_event_syscall_exit("sys"#sname); \
+ } \
+ static void unreg_exit_##sname(void) \
+ { \
+ unreg_event_syscall_exit("sys"#sname); \
+ } \
+ 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_exit_##sname, \
+ .unregfunc = unreg_exit_##sname, \
+ }
+
#define SYSCALL_METADATA(sname, nb) \
static const struct syscall_metadata __used \
__attribute__((__aligned__(4))) \
@@ -121,7 +189,9 @@ 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 +201,9 @@ 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 4416c6f..53e7d14 100644
--- a/include/trace/syscall.h
+++ b/include/trace/syscall.h
@@ -3,6 +3,8 @@

#include <asm/ptrace.h>
#include <linux/tracepoint.h>
+#include <linux/unistd.h>
+#include <linux/ftrace_event.h>

extern void syscall_regfunc(void);
extern void syscall_unregfunc(void);
@@ -38,15 +40,13 @@ 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(char *name);
+extern void unreg_event_syscall_enter(char *name);
+extern int reg_event_syscall_exit(char *name);
+extern void unreg_event_syscall_exit(char *name);
#endif

#endif /* _TRACE_SYSCALL_H */
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 08aed43..cc283d6 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 + 1);
+static DECLARE_BITMAP(enabled_exit_syscalls, FTRACE_SYSCALL_MAX + 1);

/* 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 +155,86 @@ 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(char *name)
{
- start_ftrace_syscalls();
+ int ret = 0;
+ int num;

- return 0;
+ 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(char *name)
{
- 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;

-static struct tracer syscall_tracer __read_mostly = {
- .name = "syscall",
- .init = init_syscall_tracer,
- .reset = reset_syscall_tracer,
- .flags = &syscalls_flags,
-};
+ 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(char *name)
{
- int ret;
+ int ret = 0;
+ int num;

- 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);
+ 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(char *name)
+{
+ int num;

- return register_tracer(&syscall_tracer);
+ 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
+};
--
1.6.0.6


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