Commit 643ad838 authored by Tejun Heo's avatar Tejun Heo Committed by Oleg Nesterov
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
parent d21142ec

include/linux/ptrace.h

+32 −14
Original line number Diff line number Diff line
@@ -90,12 +90,17 @@ 
#define PT_DTRACE	0x00000002	/* delayed trace (used on m68k, i386) */

#define PT_TRACESYSGOOD	0x00000004

#define PT_PTRACE_CAP	0x00000008	/* ptracer can follow suid-exec */

#define PT_TRACE_FORK	0x00000010

#define PT_TRACE_VFORK	0x00000020

#define PT_TRACE_CLONE	0x00000040

#define PT_TRACE_EXEC	0x00000080

#define PT_TRACE_VFORK_DONE	0x00000100

#define PT_TRACE_EXIT	0x00000200



/* PT_TRACE_* event enable flags */

#define PT_EVENT_FLAG_SHIFT	4

#define PT_EVENT_FLAG(event)	(1 << (PT_EVENT_FLAG_SHIFT + (event) - 1))



#define PT_TRACE_FORK		PT_EVENT_FLAG(PTRACE_EVENT_FORK)

#define PT_TRACE_VFORK		PT_EVENT_FLAG(PTRACE_EVENT_VFORK)

#define PT_TRACE_CLONE		PT_EVENT_FLAG(PTRACE_EVENT_CLONE)

#define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)

#define PT_TRACE_VFORK_DONE	PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)

#define PT_TRACE_EXIT		PT_EVENT_FLAG(PTRACE_EVENT_EXIT)



#define PT_TRACE_MASK	0x000003f4
@@ -145,26 +150,39 @@ int generic_ptrace_peekdata(struct task_struct *tsk, unsigned long addr, 
int generic_ptrace_pokedata(struct task_struct *tsk, unsigned long addr,

			    unsigned long data);



/**

 * ptrace_event_enabled - test whether a ptrace event is enabled

 * @task: ptracee of interest

 * @event: %PTRACE_EVENT_* to test

 *

 * Test whether @event is enabled for ptracee @task.

 *

 * Returns %true if @event is enabled, %false otherwise.

 */

static inline bool ptrace_event_enabled(struct task_struct *task, int event)

{

	return task->ptrace & PT_EVENT_FLAG(event);

}



/**

 * ptrace_event - possibly stop for a ptrace event notification

 * @mask:	%PT_* bit to check in @current->ptrace

 * @event:	%PTRACE_EVENT_* value to report if @mask is set

 * @event:	%PTRACE_EVENT_* value to report

 * @message:	value for %PTRACE_GETEVENTMSG to return

 *

 * This checks the @mask bit to see if ptrace wants stops for this event.

 * If so we stop, reporting @event and @message to the ptrace parent.

 * Check whether @event is enabled and, if so, report @event and @message

 * to the ptrace parent.

 *

 * Returns nonzero if we did a ptrace notification, zero if not.

 *

 * Called without locks.

 */

static inline int ptrace_event(int mask, int event, unsigned long message)

static inline int ptrace_event(int event, unsigned long message)

{

	if (mask && likely(!(current->ptrace & mask)))

		return 0;

	if (likely(!ptrace_event_enabled(current, event)))

		return false;

	current->ptrace_message = message;

	ptrace_notify((event << 8) | SIGTRAP);

	return 1;

	return true;

}



/**

include/linux/tracehook.h

+13 −13
Original line number Diff line number Diff line
@@ -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);

}



/**

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