Add code to support debugging threaded process.

1. Add tm_lwpid into kse_thr_mailbox to indicate which kernel
   thread current user thread is running on. Add tm_dflags into
   kse_thr_mailbox, the flags is written by debugger, it tells
   UTS and kernel what should be done when the process is being
   debugged, current, there two flags TMDF_SSTEP and TMDF_DONOTRUNUSER.

   TMDF_SSTEP is used to tell kernel to turn on single stepping,
   or turn off if it is not set.

   TMDF_DONOTRUNUSER is used to tell kernel to schedule upcall
   whenever possible, to UTS, it means do not run the user thread
   until debugger clears it, this behaviour is necessary because
   gdb wants to resume only one thread when the thread's pc is
   at a breakpoint, and thread needs to go forward, in order to
   avoid other threads sneak pass the breakpoints, it needs to remove
   breakpoint, only wants one thread to go. Also, add km_lwp to
   kse_mailbox, the lwp id is copied to kse_thr_mailbox at context
   switch time when process is not being debugged, so when process
   is attached, debugger can map kernel thread to user thread.

2. Add p_xthread to proc strcuture and td_xsig to thread structure.
   p_xthread is used by a thread when it wants to report event
   to debugger, every thread can set the pointer, especially, when
   it is used in ptracestop, it is the last thread reporting event
   will win the race. Every thread has a td_xsig to exchange signal
   with debugger, thread uses TDF_XSIG flag to indicate it is reporting
   signal to debugger, if the flag is not cleared, thread will keep
   retrying until it is cleared by debugger, p_xthread may be
   used by debugger to indicate CURRENT thread. The p_xstat is still
   in proc structure to keep wait() to work, in future, we may
   just use td_xsig.

3. Add TDF_DBSUSPEND flag, the flag is used by debugger to suspend
   a thread. When process stops, debugger can set the flag for
   thread, thread will check the flag in thread_suspend_check,
   enters a loop, unless it is cleared by debugger, process is
   detached or process is existing. The flag is also checked in
   ptracestop, so debugger can temporarily suspend a thread even
   if the thread wants to exchange signal.

4. Current, in ptrace, we always resume all threads, but if a thread
   has already a TDF_DBSUSPEND flag set by debugger, it won't run.

Encouraged by: marcel, julian, deischen

1 files changed, 31 insertions, 21 deletions

diff --git a/sys/sys/kse.h b/sys/sys/kse.h
index 2d02eb788395..a0a2752a2503 100644
--- a/sys/sys/kse.h
+++ b/sys/sys/kse.h
@@ -54,13 +54,15 @@ typedef void	kse_func_t(struct kse_mailbox *);
  */
 struct kse_thr_mailbox {
 	ucontext_t		tm_context;	/* User and machine context */
-	unsigned int		tm_flags;	/* Thread flags */
+	uint32_t		tm_flags;	/* Thread flags */
 	struct kse_thr_mailbox	*tm_next;	/* Next thread in list */
 	void			*tm_udata;	/* For use by the UTS */
-	uint32_t		tm_uticks;
-	uint32_t		tm_sticks;
+	uint32_t		tm_uticks;	/* Time in userland */
+	uint32_t		tm_sticks;	/* Time in kernel */
 	siginfo_t		tm_syncsig;
-	int			tm_spare[8];
+	uint32_t		tm_dflags;	/* Debug flags */
+	lwpid_t			tm_lwp;		/* kernel thread UTS runs on */
+	uint32_t		__spare__[6];
 };
 
 /*
@@ -70,40 +72,48 @@ struct kse_thr_mailbox {
  * a single KSE.
  */
 struct kse_mailbox {
-	int			km_version;	/* Mailbox version */
+	uint32_t		km_version;	/* Mailbox version */
 	struct kse_thr_mailbox	*km_curthread;	/* Currently running thread */
 	struct kse_thr_mailbox	*km_completed;	/* Threads back from kernel */
 	sigset_t		km_sigscaught;	/* Caught signals */
-	uint32_t		km_flags;	/* KSE flags */
+	uint32_t		km_flags;	/* Mailbox flags */
 	kse_func_t		*km_func;	/* UTS function */
-	stack_t			km_stack;	/* UTS context */
+	stack_t			km_stack;	/* UTS stack */
 	void			*km_udata;	/* For use by the UTS */
 	struct timespec		km_timeofday;	/* Time of day */
-	int			km_quantum;	/* Upcall quantum in msecs */
-	int			km_spare[8];
+	uint32_t		km_quantum;	/* Upcall quantum in msecs */
+	lwpid_t			km_lwp;		/* kernel thread UTS runs on */
+	uint32_t		__spare2__[7];
 };
 
-#define	KSE_VER_0	0
-#define	KSE_VERSION	KSE_VER_0
+#define KSE_VER_0		0
+#define KSE_VERSION		KSE_VER_0
 
 /* These flags are kept in km_flags */
-#define	KMF_NOUPCALL		0x01
-#define	KMF_NOCOMPLETED		0x02
-#define	KMF_DONE		0x04
-#define	KMF_BOUND		0x08
-#define	KMF_WAITSIGEVENT	0x10
+#define KMF_NOUPCALL		0x01
+#define KMF_NOCOMPLETED		0x02
+#define KMF_DONE		0x04
+#define KMF_BOUND		0x08
+#define KMF_WAITSIGEVENT	0x10
 
 /* These flags are kept in tm_flags */
-#define	TMF_NOUPCALL		0x01
+#define TMF_NOUPCALL		0x01
+
+/* These flags are kept in tm_dlfags */
+#define TMDF_SSTEP		0x01
+#define TMDF_DONOTRUNUSER	0x02
+
+/* Flags for kse_switchin */
+#define KSE_SWITCHIN_SETTMBX	0x01
 
 /* Flags for kse_switchin */
 #define KSE_SWITCHIN_SETTMBX	0x01
 
 /* Commands for kse_thr_interrupt */
-#define	KSE_INTR_INTERRUPT	0x01
-#define	KSE_INTR_RESTART	0x02
-#define	KSE_INTR_SENDSIG	0x03
-#define	KSE_INTR_SIGEXIT	0x04
+#define KSE_INTR_INTERRUPT	0x01
+#define KSE_INTR_RESTART	0x02
+#define KSE_INTR_SENDSIG	0x03
+#define KSE_INTR_SIGEXIT	0x04
 
 #ifndef _KERNEL
 int	kse_create(struct kse_mailbox *, int);