ptrace: introduce ptrace_event_enabled() and simplify ptrace_event() and tracehook_prepare_clone()

This patch implements ptrace_event_enabled() which tests whether a
given PTRACE_EVENT_* is enabled and use it to simplify ptrace_event()
and tracehook_prepare_clone().

PT_EVENT_FLAG() macro is added which calculates PT_TRACE_* flag from
PTRACE_EVENT_*.  This is used to define PT_TRACE_* flags and by
ptrace_event_enabled() to find the matching flag.

This is used to make ptrace_event() and tracehook_prepare_clone()
simpler.

* ptrace_event() callers were responsible for providing mask to test
  whether the event was enabled.  This patch implements
  ptrace_event_enabled() and make ptrace_event() drop @mask and
  determine whether the event is enabled from @event.  Note that
  @event is constant and this conversion doesn't add runtime overhead.

  All conversions except tracehook_report_clone_complete() are
  trivial.  tracehook_report_clone_complete() used to use 0 for @mask
  (always enabled) but now tests whether the specified event is
  enabled.  This doesn't cause any behavior difference as it's
  guaranteed that the event specified by @trace is enabled.

* tracehook_prepare_clone() now only determines which event is
  applicable and use ptrace_event_enabled() for enable test.

This doesn't introduce any behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>

1 files changed, 13 insertions, 13 deletions

diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index a3e838784f43..7d38571b0c05 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -201,7 +201,7 @@ static inline void tracehook_report_exec(struct linux_binfmt *fmt,
                                          struct linux_binprm *bprm,
                                          struct pt_regs *regs)
 {
-        if (!ptrace_event(PT_TRACE_EXEC, PTRACE_EVENT_EXEC, 0) &&
+        if (!ptrace_event(PTRACE_EVENT_EXEC, 0) &&
             unlikely(current->ptrace & PT_PTRACED))
                 send_sig(SIGTRAP, current, 0);
 }
@@ -218,7 +218,7 @@ static inline void tracehook_report_exec(struct linux_binfmt *fmt,
  */
 static inline void tracehook_report_exit(long *exit_code)
 {
-        ptrace_event(PT_TRACE_EXIT, PTRACE_EVENT_EXIT, *exit_code);
+        ptrace_event(PTRACE_EVENT_EXIT, *exit_code);
 }
 
 /**
@@ -232,19 +232,19 @@ static inline void tracehook_report_exit(long *exit_code)
  */
 static inline int tracehook_prepare_clone(unsigned clone_flags)
 {
+        int event = 0;
+
         if (clone_flags & CLONE_UNTRACED)
                 return 0;
 
-        if (clone_flags & CLONE_VFORK) {
-                if (current->ptrace & PT_TRACE_VFORK)
-                        return PTRACE_EVENT_VFORK;
-        } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
-                if (current->ptrace & PT_TRACE_CLONE)
-                        return PTRACE_EVENT_CLONE;
-        } else if (current->ptrace & PT_TRACE_FORK)
-                return PTRACE_EVENT_FORK;
+        if (clone_flags & CLONE_VFORK)
+                event = PTRACE_EVENT_VFORK;
+        else if ((clone_flags & CSIGNAL) != SIGCHLD)
+                event = PTRACE_EVENT_CLONE;
+        else
+                event = PTRACE_EVENT_FORK;
 
-        return 0;
+        return ptrace_event_enabled(current, event) ? event : 0;
 }
 
 /**
@@ -318,7 +318,7 @@ static inline void tracehook_report_clone_complete(int trace,
                                                    struct task_struct *child)
 {
         if (unlikely(trace))
-                ptrace_event(0, trace, pid);
+                ptrace_event(trace, pid);
 }
 
 /**
@@ -336,7 +336,7 @@ static inline void tracehook_report_clone_complete(int trace,
 static inline void tracehook_report_vfork_done(struct task_struct *child,
                                                pid_t pid)
 {
-        ptrace_event(PT_TRACE_VFORK_DONE, PTRACE_EVENT_VFORK_DONE, pid);
+        ptrace_event(PTRACE_EVENT_VFORK_DONE, pid);
 }
 
 /**