svn commit: r292894 - in head: sys/kern sys/sys tests/sys/kern
John Baldwin
jhb at FreeBSD.org
Tue Dec 29 23:25:27 UTC 2015
Author: jhb
Date: Tue Dec 29 23:25:26 2015
New Revision: 292894
URL: https://svnweb.freebsd.org/changeset/base/292894
Log:
Add ptrace(2) reporting for LWP events.
Add two new LWPINFO flags: PL_FLAG_BORN and PL_FLAG_EXITED for reporting
thread creation and destruction. Newly created threads will stop to report
PL_FLAG_BORN before returning to userland and exiting threads will stop to
report PL_FLAG_EXIT before exiting completely. Both of these events are
only enabled and reported if PT_LWP_EVENTS is enabled on a process.
Modified:
head/sys/kern/kern_fork.c
head/sys/kern/kern_sig.c
head/sys/kern/kern_thr.c
head/sys/kern/sys_process.c
head/sys/sys/proc.h
head/sys/sys/ptrace.h
head/tests/sys/kern/ptrace_test.c
Modified: head/sys/kern/kern_fork.c
==============================================================================
--- head/sys/kern/kern_fork.c Tue Dec 29 23:24:10 2015 (r292893)
+++ head/sys/kern/kern_fork.c Tue Dec 29 23:25:26 2015 (r292894)
@@ -1066,7 +1066,7 @@ fork_return(struct thread *td, struct tr
cv_broadcast(&p->p_dbgwait);
}
PROC_UNLOCK(p);
- } else if (p->p_flag & P_TRACED) {
+ } else if (p->p_flag & P_TRACED || td->td_dbgflags & TDB_BORN) {
/*
* This is the start of a new thread in a traced
* process. Report a system call exit event.
@@ -1074,9 +1074,10 @@ fork_return(struct thread *td, struct tr
PROC_LOCK(p);
td->td_dbgflags |= TDB_SCX;
_STOPEVENT(p, S_SCX, td->td_dbg_sc_code);
- if ((p->p_stops & S_PT_SCX) != 0)
+ if ((p->p_stops & S_PT_SCX) != 0 ||
+ (td->td_dbgflags & TDB_BORN) != 0)
ptracestop(td, SIGTRAP);
- td->td_dbgflags &= ~TDB_SCX;
+ td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
PROC_UNLOCK(p);
}
Modified: head/sys/kern/kern_sig.c
==============================================================================
--- head/sys/kern/kern_sig.c Tue Dec 29 23:24:10 2015 (r292893)
+++ head/sys/kern/kern_sig.c Tue Dec 29 23:25:26 2015 (r292894)
@@ -2501,7 +2501,12 @@ ptracestop(struct thread *td, int sig)
td->td_tid, p->p_pid, td->td_dbgflags, sig);
PROC_SLOCK(p);
while ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_XSIG)) {
- if (p->p_flag & P_SINGLE_EXIT) {
+ if (p->p_flag & P_SINGLE_EXIT &&
+ !(td->td_dbgflags & TDB_EXIT)) {
+ /*
+ * Ignore ptrace stops except for thread exit
+ * events when the process exits.
+ */
td->td_dbgflags &= ~TDB_XSIG;
PROC_SUNLOCK(p);
return (sig);
Modified: head/sys/kern/kern_thr.c
==============================================================================
--- head/sys/kern/kern_thr.c Tue Dec 29 23:24:10 2015 (r292893)
+++ head/sys/kern/kern_thr.c Tue Dec 29 23:25:26 2015 (r292894)
@@ -253,6 +253,8 @@ thread_create(struct thread *td, struct
thread_unlock(td);
if (P_SHOULDSTOP(p))
newtd->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
+ if (p->p_flag2 & P2_LWP_EVENTS)
+ newtd->td_dbgflags |= TDB_BORN;
/*
* Copy the existing thread VM policy into the new thread.
@@ -322,29 +324,54 @@ kern_thr_exit(struct thread *td)
p = td->td_proc;
- rw_wlock(&tidhash_lock);
+ /*
+ * If all of the threads in a process call this routine to
+ * exit (e.g. all threads call pthread_exit()), exactly one
+ * thread should return to the caller to terminate the process
+ * instead of the thread.
+ *
+ * Checking p_numthreads alone is not sufficient since threads
+ * might be committed to terminating while the PROC_LOCK is
+ * dropped in either ptracestop() or while removing this thread
+ * from the tidhash. Instead, the p_pendingexits field holds
+ * the count of threads in either of those states and a thread
+ * is considered the "last" thread if all of the other threads
+ * in a process are already terminating.
+ */
PROC_LOCK(p);
-
- if (p->p_numthreads != 1) {
- racct_sub(p, RACCT_NTHR, 1);
- LIST_REMOVE(td, td_hash);
- rw_wunlock(&tidhash_lock);
- tdsigcleanup(td);
- umtx_thread_exit(td);
- PROC_SLOCK(p);
- thread_stopped(p);
- thread_exit();
- /* NOTREACHED */
+ if (p->p_numthreads == p->p_pendingexits + 1) {
+ /*
+ * Ignore attempts to shut down last thread in the
+ * proc. This will actually call _exit(2) in the
+ * usermode trampoline when it returns.
+ */
+ PROC_UNLOCK(p);
+ return (0);
}
+ p->p_pendingexits++;
+ td->td_dbgflags |= TDB_EXIT;
+ if (p->p_flag & P_TRACED && p->p_flag2 & P2_LWP_EVENTS)
+ ptracestop(td, SIGTRAP);
+ PROC_UNLOCK(p);
+ tidhash_remove(td);
+ PROC_LOCK(p);
+ p->p_pendingexits--;
+
/*
- * Ignore attempts to shut down last thread in the proc. This
- * will actually call _exit(2) in the usermode trampoline when
- * it returns.
+ * The check above should prevent all other threads from this
+ * process from exiting while the PROC_LOCK is dropped, so
+ * there must be at least one other thread other than the
+ * current thread.
*/
- PROC_UNLOCK(p);
- rw_wunlock(&tidhash_lock);
- return (0);
+ KASSERT(p->p_numthreads > 1, ("too few threads"));
+ racct_sub(p, RACCT_NTHR, 1);
+ tdsigcleanup(td);
+ umtx_thread_exit(td);
+ PROC_SLOCK(p);
+ thread_stopped(p);
+ thread_exit();
+ /* NOTREACHED */
}
int
Modified: head/sys/kern/sys_process.c
==============================================================================
--- head/sys/kern/sys_process.c Tue Dec 29 23:24:10 2015 (r292893)
+++ head/sys/kern/sys_process.c Tue Dec 29 23:25:26 2015 (r292894)
@@ -710,6 +710,7 @@ kern_ptrace(struct thread *td, int req,
case PT_TO_SCX:
case PT_SYSCALL:
case PT_FOLLOW_FORK:
+ case PT_LWP_EVENTS:
case PT_DETACH:
sx_xlock(&proctree_lock);
proctree_locked = 1;
@@ -948,6 +949,16 @@ kern_ptrace(struct thread *td, int req,
p->p_flag &= ~P_FOLLOWFORK;
break;
+ case PT_LWP_EVENTS:
+ CTR3(KTR_PTRACE, "PT_LWP_EVENTS: pid %d %s -> %s", p->p_pid,
+ p->p_flag2 & P2_LWP_EVENTS ? "enabled" : "disabled",
+ data ? "enabled" : "disabled");
+ if (data)
+ p->p_flag2 |= P2_LWP_EVENTS;
+ else
+ p->p_flag2 &= ~P2_LWP_EVENTS;
+ break;
+
case PT_STEP:
case PT_CONTINUE:
case PT_TO_SCE:
@@ -1252,6 +1263,10 @@ kern_ptrace(struct thread *td, int req,
}
if (td2->td_dbgflags & TDB_CHILD)
pl->pl_flags |= PL_FLAG_CHILD;
+ if (td2->td_dbgflags & TDB_BORN)
+ pl->pl_flags |= PL_FLAG_BORN;
+ if (td2->td_dbgflags & TDB_EXIT)
+ pl->pl_flags |= PL_FLAG_EXITED;
pl->pl_sigmask = td2->td_sigmask;
pl->pl_siglist = td2->td_siglist;
strcpy(pl->pl_tdname, td2->td_name);
Modified: head/sys/sys/proc.h
==============================================================================
--- head/sys/sys/proc.h Tue Dec 29 23:24:10 2015 (r292893)
+++ head/sys/sys/proc.h Tue Dec 29 23:25:26 2015 (r292894)
@@ -412,6 +412,8 @@ do { \
#define TDB_STOPATFORK 0x00000080 /* Stop at the return from fork (child
only) */
#define TDB_CHILD 0x00000100 /* New child indicator for ptrace() */
+#define TDB_BORN 0x00000200 /* New LWP indicator for ptrace() */
+#define TDB_EXIT 0x00000400 /* Exiting LWP indicator for ptrace() */
/*
* "Private" flags kept in td_pflags:
@@ -577,6 +579,7 @@ struct proc {
struct itimers *p_itimers; /* (c) POSIX interval timers. */
struct procdesc *p_procdesc; /* (e) Process descriptor, if any. */
u_int p_treeflag; /* (e) P_TREE flags */
+ int p_pendingexits; /* (c) Count of pending thread exits. */
/* End area that is zeroed on creation. */
#define p_endzero p_magic
@@ -695,6 +698,7 @@ struct proc {
#define P2_NOTRACE 0x00000002 /* No ptrace(2) attach or coredumps. */
#define P2_NOTRACE_EXEC 0x00000004 /* Keep P2_NOPTRACE on exec(2). */
#define P2_AST_SU 0x00000008 /* Handles SU ast for kthreads. */
+#define P2_LWP_EVENTS 0x00000010 /* Report LWP events via ptrace(2). */
/* Flags protected by proctree_lock, kept in p_treeflags. */
#define P_TREE_ORPHANED 0x00000001 /* Reparented, on orphan list */
Modified: head/sys/sys/ptrace.h
==============================================================================
--- head/sys/sys/ptrace.h Tue Dec 29 23:24:10 2015 (r292893)
+++ head/sys/sys/ptrace.h Tue Dec 29 23:25:26 2015 (r292894)
@@ -64,6 +64,7 @@
#define PT_SYSCALL 22
#define PT_FOLLOW_FORK 23
+#define PT_LWP_EVENTS 24 /* report LWP birth and exit */
#define PT_GETREGS 33 /* get general-purpose registers */
#define PT_SETREGS 34 /* set general-purpose registers */
@@ -108,6 +109,8 @@ struct ptrace_lwpinfo {
#define PL_FLAG_SI 0x20 /* siginfo is valid */
#define PL_FLAG_FORKED 0x40 /* new child */
#define PL_FLAG_CHILD 0x80 /* I am from child */
+#define PL_FLAG_BORN 0x100 /* new LWP */
+#define PL_FLAG_EXITED 0x200 /* exiting LWP */
sigset_t pl_sigmask; /* LWP signal mask */
sigset_t pl_siglist; /* LWP pending signal */
struct __siginfo pl_siginfo; /* siginfo for signal */
Modified: head/tests/sys/kern/ptrace_test.c
==============================================================================
--- head/tests/sys/kern/ptrace_test.c Tue Dec 29 23:24:10 2015 (r292893)
+++ head/tests/sys/kern/ptrace_test.c Tue Dec 29 23:25:26 2015 (r292894)
@@ -1094,6 +1094,16 @@ simple_thread(void *arg __unused)
pthread_exit(NULL);
}
+static __dead2 void
+simple_thread_main(void)
+{
+ pthread_t thread;
+
+ CHILD_REQUIRE(pthread_create(&thread, NULL, simple_thread, NULL) == 0);
+ CHILD_REQUIRE(pthread_join(thread, NULL) == 0);
+ exit(1);
+}
+
/*
* Verify that pl_syscall_code in struct ptrace_lwpinfo for a new
* thread reports the correct value.
@@ -1108,14 +1118,8 @@ ATF_TC_BODY(ptrace__new_child_pl_syscall
ATF_REQUIRE((fpid = fork()) != -1);
if (fpid == 0) {
- pthread_t thread;
-
trace_me();
-
- CHILD_REQUIRE(pthread_create(&thread, NULL, simple_thread,
- NULL) == 0);
- CHILD_REQUIRE(pthread_join(thread, NULL) == 0);
- exit(1);
+ simple_thread_main();
}
/* The first wait() should report the stop from SIGSTOP. */
@@ -1178,6 +1182,179 @@ ATF_TC_BODY(ptrace__new_child_pl_syscall
ATF_REQUIRE(errno == ECHILD);
}
+/*
+ * Verify that the expected LWP events are reported for a child thread.
+ */
+ATF_TC_WITHOUT_HEAD(ptrace__lwp_events);
+ATF_TC_BODY(ptrace__lwp_events, tc)
+{
+ struct ptrace_lwpinfo pl;
+ pid_t fpid, wpid;
+ lwpid_t lwps[2];
+ int status;
+
+ ATF_REQUIRE((fpid = fork()) != -1);
+ if (fpid == 0) {
+ trace_me();
+ simple_thread_main();
+ }
+
+ /* The first wait() should report the stop from SIGSTOP. */
+ wpid = waitpid(fpid, &status, 0);
+ ATF_REQUIRE(wpid == fpid);
+ ATF_REQUIRE(WIFSTOPPED(status));
+ ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
+
+ ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl,
+ sizeof(pl)) != -1);
+ lwps[0] = pl.pl_lwpid;
+
+ ATF_REQUIRE(ptrace(PT_LWP_EVENTS, wpid, NULL, 1) == 0);
+
+ /* Continue the child ignoring the SIGSTOP. */
+ ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
+
+ /* The first event should be for the child thread's birth. */
+ wpid = waitpid(fpid, &status, 0);
+ ATF_REQUIRE(wpid == fpid);
+ ATF_REQUIRE(WIFSTOPPED(status));
+ ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
+
+ ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
+ ATF_REQUIRE((pl.pl_flags & (PL_FLAG_BORN | PL_FLAG_SCX)) ==
+ (PL_FLAG_BORN | PL_FLAG_SCX));
+ ATF_REQUIRE(pl.pl_lwpid != lwps[0]);
+ lwps[1] = pl.pl_lwpid;
+
+ ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
+
+ /* The next event should be for the child thread's death. */
+ wpid = waitpid(fpid, &status, 0);
+ ATF_REQUIRE(wpid == fpid);
+ ATF_REQUIRE(WIFSTOPPED(status));
+ ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
+
+ ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
+ ATF_REQUIRE((pl.pl_flags & (PL_FLAG_EXITED | PL_FLAG_SCE)) ==
+ (PL_FLAG_EXITED | PL_FLAG_SCE));
+ ATF_REQUIRE(pl.pl_lwpid == lwps[1]);
+
+ ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
+
+ /* The last event should be for the child process's exit. */
+ wpid = waitpid(fpid, &status, 0);
+ ATF_REQUIRE(WIFEXITED(status));
+ ATF_REQUIRE(WEXITSTATUS(status) == 1);
+
+ wpid = wait(&status);
+ ATF_REQUIRE(wpid == -1);
+ ATF_REQUIRE(errno == ECHILD);
+}
+
+static void *
+exec_thread(void *arg __unused)
+{
+
+ execl("/usr/bin/true", "true", NULL);
+ exit(127);
+}
+
+static __dead2 void
+exec_thread_main(void)
+{
+ pthread_t thread;
+
+ CHILD_REQUIRE(pthread_create(&thread, NULL, exec_thread, NULL) == 0);
+ for (;;)
+ sleep(60);
+ exit(1);
+}
+
+/*
+ * Verify that the expected LWP events are reported for a multithreaded
+ * process that calls execve(2).
+ */
+ATF_TC_WITHOUT_HEAD(ptrace__lwp_events_exec);
+ATF_TC_BODY(ptrace__lwp_events_exec, tc)
+{
+ struct ptrace_lwpinfo pl;
+ pid_t fpid, wpid;
+ lwpid_t lwps[2];
+ int status;
+
+ ATF_REQUIRE((fpid = fork()) != -1);
+ if (fpid == 0) {
+ trace_me();
+ exec_thread_main();
+ }
+
+ /* The first wait() should report the stop from SIGSTOP. */
+ wpid = waitpid(fpid, &status, 0);
+ ATF_REQUIRE(wpid == fpid);
+ ATF_REQUIRE(WIFSTOPPED(status));
+ ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
+
+ ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl,
+ sizeof(pl)) != -1);
+ lwps[0] = pl.pl_lwpid;
+
+ ATF_REQUIRE(ptrace(PT_LWP_EVENTS, wpid, NULL, 1) == 0);
+
+ /* Continue the child ignoring the SIGSTOP. */
+ ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
+
+ /* The first event should be for the child thread's birth. */
+ wpid = waitpid(fpid, &status, 0);
+ ATF_REQUIRE(wpid == fpid);
+ ATF_REQUIRE(WIFSTOPPED(status));
+ ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
+
+ ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
+ ATF_REQUIRE((pl.pl_flags & (PL_FLAG_BORN | PL_FLAG_SCX)) ==
+ (PL_FLAG_BORN | PL_FLAG_SCX));
+ ATF_REQUIRE(pl.pl_lwpid != lwps[0]);
+ lwps[1] = pl.pl_lwpid;
+
+ ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
+
+ /*
+ * The next event should be for the main thread's death due to
+ * single threading from execve().
+ */
+ wpid = waitpid(fpid, &status, 0);
+ ATF_REQUIRE(wpid == fpid);
+ ATF_REQUIRE(WIFSTOPPED(status));
+ ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
+
+ ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
+ ATF_REQUIRE((pl.pl_flags & (PL_FLAG_EXITED | PL_FLAG_SCE)) ==
+ (PL_FLAG_EXITED));
+ ATF_REQUIRE(pl.pl_lwpid == lwps[0]);
+
+ ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
+
+ /* The next event should be for the child process's exec. */
+ wpid = waitpid(fpid, &status, 0);
+ ATF_REQUIRE(WIFSTOPPED(status));
+ ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
+
+ ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
+ ATF_REQUIRE((pl.pl_flags & (PL_FLAG_EXEC | PL_FLAG_SCX)) ==
+ (PL_FLAG_EXEC | PL_FLAG_SCX));
+ ATF_REQUIRE(pl.pl_lwpid == lwps[1]);
+
+ ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
+
+ /* The last event should be for the child process's exit. */
+ wpid = waitpid(fpid, &status, 0);
+ ATF_REQUIRE(WIFEXITED(status));
+ ATF_REQUIRE(WEXITSTATUS(status) == 0);
+
+ wpid = wait(&status);
+ ATF_REQUIRE(wpid == -1);
+ ATF_REQUIRE(errno == ECHILD);
+}
+
ATF_TP_ADD_TCS(tp)
{
@@ -1197,6 +1374,8 @@ ATF_TP_ADD_TCS(tp)
ATF_TP_ADD_TC(tp, ptrace__new_child_pl_syscall_code_fork);
ATF_TP_ADD_TC(tp, ptrace__new_child_pl_syscall_code_vfork);
ATF_TP_ADD_TC(tp, ptrace__new_child_pl_syscall_code_thread);
+ ATF_TP_ADD_TC(tp, ptrace__lwp_events);
+ ATF_TP_ADD_TC(tp, ptrace__lwp_events_exec);
return (atf_no_error());
}
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