Add a mask of optional ptrace() events.

ptrace() now stores a mask of optional events in p_ptevents.  Currently
this mask is a single integer, but it can be expanded into an array of
integers in the future.

Two new ptrace requests can be used to manipulate the event mask:
PT_GET_EVENT_MASK fetches the current event mask and PT_SET_EVENT_MASK
sets the current event mask.

The current set of events include:
- PTRACE_EXEC: trace calls to execve().
- PTRACE_SCE: trace system call entries.
- PTRACE_SCX: trace syscam call exits.
- PTRACE_FORK: trace forks and auto-attach to new child processes.
- PTRACE_LWP: trace LWP events.

The S_PT_SCX and S_PT_SCE events in the procfs p_stops flags have
been replaced by PTRACE_SCE and PTRACE_SCX.  PTRACE_FORK replaces
P_FOLLOW_FORK and PTRACE_LWP replaces P2_LWP_EVENTS.

The PT_FOLLOW_FORK and PT_LWP_EVENTS ptrace requests remain for
compatibility but now simply toggle corresponding flags in the
event mask.

While here, document that PT_SYSCALL, PT_TO_SCE, and PT_TO_SCX both
modify the event mask and continue the traced process.

Reviewed by:	kib
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D7044

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/kern/subr_syscall.c b/sys/kern/subr_syscall.c
index f7bbdfbadd13..aad2a1e4b930 100644
--- a/sys/kern/subr_syscall.c
+++ b/sys/kern/subr_syscall.c
@@ -87,7 +87,7 @@ syscallenter(struct thread *td, struct syscall_args *sa)
 			PROC_LOCK(p);
 			td->td_dbg_sc_code = sa->code;
 			td->td_dbg_sc_narg = sa->narg;
-			if (p->p_stops & S_PT_SCE)
+			if (p->p_ptevents & PTRACE_SCE)
 				ptracestop((td), SIGTRAP);
 			PROC_UNLOCK(p);
 		}
@@ -208,7 +208,7 @@ syscallret(struct thread *td, int error, struct syscall_args *sa)
 		 */
 		if (traced &&
 		    ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
-		    (p->p_stops & S_PT_SCX) != 0))
+		    (p->p_ptevents & PTRACE_SCX) != 0))
 			ptracestop(td, SIGTRAP);
 		td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
 		PROC_UNLOCK(p);