The original SOFT_DISABLE patches didn't add support for soft disable
of syscall events; this adds it and paves the way for future patches
allowing triggers to be added to syscall events, since triggers are
built on top of SOFT_DISABLE.
Add an array of ftrace_event_file pointers indexed by syscall number
to the trace array and remove the existing enabled bitmaps, which as a
result are now redundant. The ftrace_event_file structs in turn
contain the soft disable flags we need for per-syscall soft disable
accounting; later patches add additional 'trigger' flags and
per-syscall triggers and filters.
Signed-off-by: Tom Zanussi <tom.zanu...@linux.intel.com>
---
kernel/trace/trace.h | 4 ++--
kernel/trace/trace_syscalls.c | 36 ++++++++++++++++++++++++++++++------
2 files changed, 32 insertions(+), 8 deletions(-)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index fe39acd..b1227b9 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -192,8 +192,8 @@ struct trace_array {
#ifdef CONFIG_FTRACE_SYSCALLS
int sys_refcount_enter;
int sys_refcount_exit;
- DECLARE_BITMAP(enabled_enter_syscalls, NR_syscalls);
- DECLARE_BITMAP(enabled_exit_syscalls, NR_syscalls);
+ struct ftrace_event_file *enter_syscall_files[NR_syscalls];
+ struct ftrace_event_file *exit_syscall_files[NR_syscalls];
#endif
int stop_count;
int clock_id;
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 559329d..230cdb6 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -302,6 +302,7 @@ static int __init syscall_exit_define_fields(struct
ftrace_event_call *call)
static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
{
struct trace_array *tr = data;
+ struct ftrace_event_file *ftrace_file;
struct syscall_trace_enter *entry;
struct syscall_metadata *sys_data;
struct ring_buffer_event *event;
@@ -314,7 +315,13 @@ static void ftrace_syscall_enter(void *data, struct
pt_regs *regs, long id)
syscall_nr = trace_get_syscall_nr(current, regs);
if (syscall_nr < 0)
return;
- if (!test_bit(syscall_nr, tr->enabled_enter_syscalls))
+
+ /* Here we're inside the tp handler's rcu_read_lock (__DO_TRACE()) */
+ ftrace_file = rcu_dereference_raw(tr->enter_syscall_files[syscall_nr]);
+ if (!ftrace_file)
+ return;
+
+ if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &ftrace_file->flags))
return;
sys_data = syscall_nr_to_meta(syscall_nr);
@@ -345,6 +352,7 @@ static void ftrace_syscall_enter(void *data, struct pt_regs
*regs, long id)
static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
{
struct trace_array *tr = data;
+ struct ftrace_event_file *ftrace_file;
struct syscall_trace_exit *entry;
struct syscall_metadata *sys_data;
struct ring_buffer_event *event;
@@ -356,7 +364,13 @@ static void ftrace_syscall_exit(void *data, struct pt_regs
*regs, long ret)
syscall_nr = trace_get_syscall_nr(current, regs);
if (syscall_nr < 0)
return;
- if (!test_bit(syscall_nr, tr->enabled_exit_syscalls))
+
+ /* Here we're inside the tp handler's rcu_read_lock (__DO_TRACE()) */
+ ftrace_file = rcu_dereference_raw(tr->exit_syscall_files[syscall_nr]);
+ if (!ftrace_file)
+ return;
+
+ if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &ftrace_file->flags))
return;
sys_data = syscall_nr_to_meta(syscall_nr);
@@ -397,7 +411,7 @@ static int reg_event_syscall_enter(struct ftrace_event_file
*file,
if (!tr->sys_refcount_enter)
ret = register_trace_sys_enter(ftrace_syscall_enter, tr);
if (!ret) {
- set_bit(num, tr->enabled_enter_syscalls);
+ rcu_assign_pointer(tr->enter_syscall_files[num], file);
tr->sys_refcount_enter++;
}
mutex_unlock(&syscall_trace_lock);
@@ -415,9 +429,14 @@ static void unreg_event_syscall_enter(struct
ftrace_event_file *file,
return;
mutex_lock(&syscall_trace_lock);
tr->sys_refcount_enter--;
- clear_bit(num, tr->enabled_enter_syscalls);
+ rcu_assign_pointer(tr->enter_syscall_files[num], NULL);
if (!tr->sys_refcount_enter)
unregister_trace_sys_enter(ftrace_syscall_enter, tr);
+ /*
+ * Callers expect the event to be completely disabled on
+ * return, so wait for current handlers to finish.
+ */
+ synchronize_sched();
mutex_unlock(&syscall_trace_lock);
}
@@ -435,7 +454,7 @@ static int reg_event_syscall_exit(struct ftrace_event_file
*file,
if (!tr->sys_refcount_exit)
ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
if (!ret) {
- set_bit(num, tr->enabled_exit_syscalls);
+ rcu_assign_pointer(tr->exit_syscall_files[num], file);
tr->sys_refcount_exit++;
}
mutex_unlock(&syscall_trace_lock);
@@ -453,9 +472,14 @@ static void unreg_event_syscall_exit(struct
ftrace_event_file *file,
return;
mutex_lock(&syscall_trace_lock);
tr->sys_refcount_exit--;
- clear_bit(num, tr->enabled_exit_syscalls);
+ rcu_assign_pointer(tr->exit_syscall_files[num], NULL);
if (!tr->sys_refcount_exit)
unregister_trace_sys_exit(ftrace_syscall_exit, tr);
+ /*
+ * Callers expect the event to be completely disabled on
+ * return, so wait for current handlers to finish.
+ */
+ synchronize_sched();
mutex_unlock(&syscall_trace_lock);
}
--
1.7.11.4
--
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