Author: markj
Date: Wed Dec 18 01:41:52 2013
New Revision: 259535
URL: http://svnweb.freebsd.org/changeset/base/259535
Log:
The fasttrap fork handler is responsible for removing tracepoints in the
child process that were inherited from its parent. However, this should
not be done in the case of a vfork, since the fork handler ends up removing
the tracepoints from the shared vm space, and userland DTrace probes in the
parent will no longer fire as a result.
Now the child of a vfork may trigger userland DTrace probes enabled in its
parent, so modify the fasttrap probe handler to handle this case and handle
the child process in the same way that it would handle the traced process.
In particular, if once traces function foo() in a process that vforks, and
the child calls foo(), fasttrap will treat this call as having come from the
parent. This is the behaviour of the upstream code.
While here, add #ifdef guards to some code that isn't present upstream.
MFC after: 1 month
Modified:
head/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c
head/sys/kern/kern_fork.c
Modified: head/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c Wed Dec
18 01:27:30 2013 (r259534)
+++ head/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c Wed Dec
18 01:41:52 2013 (r259535)
@@ -1001,6 +1001,9 @@ int
fasttrap_pid_probe(struct reg *rp)
{
proc_t *p = curproc;
+#if !defined(sun)
+ proc_t *pp;
+#endif
uintptr_t pc = rp->r_rip - 1;
uintptr_t new_pc = 0;
fasttrap_bucket_t *bucket;
@@ -1036,24 +1039,32 @@ fasttrap_pid_probe(struct reg *rp)
curthread->t_dtrace_regv = 0;
#endif
-#if defined(sun)
/*
* Treat a child created by a call to vfork(2) as if it were its
* parent. We know that there's only one thread of control in such a
* process: this one.
*/
+#if defined(sun)
while (p->p_flag & SVFORK) {
p = p->p_parent;
}
-#endif
- PROC_LOCK(p);
- _PHOLD(p);
pid = p->p_pid;
-#if defined(sun)
pid_mtx = &cpu_core[CPU->cpu_id].cpuc_pid_lock;
mutex_enter(pid_mtx);
+#else
+ pp = p;
+ sx_slock(&proctree_lock);
+ while (pp->p_vmspace == pp->p_pptr->p_vmspace)
+ pp = pp->p_pptr;
+ pid = pp->p_pid;
+ sx_sunlock(&proctree_lock);
+ pp = NULL;
+
+ PROC_LOCK(p);
+ _PHOLD(p);
#endif
+
bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)];
/*
@@ -1073,9 +1084,10 @@ fasttrap_pid_probe(struct reg *rp)
if (tp == NULL) {
#if defined(sun)
mutex_exit(pid_mtx);
-#endif
+#else
_PRELE(p);
PROC_UNLOCK(p);
+#endif
return (-1);
}
@@ -1197,9 +1209,10 @@ fasttrap_pid_probe(struct reg *rp)
* tracepoint again later if we need to light up any return probes.
*/
tp_local = *tp;
- PROC_UNLOCK(p);
#if defined(sun)
mutex_exit(pid_mtx);
+#else
+ PROC_UNLOCK(p);
#endif
tp = &tp_local;
@@ -1749,7 +1762,7 @@ fasttrap_pid_probe(struct reg *rp)
#if defined(sun)
if (fasttrap_copyout(scratch, (char *)addr, i)) {
#else
- if (uwrite(curproc, scratch, i, addr)) {
+ if (uwrite(p, scratch, i, addr)) {
#endif
fasttrap_sigtrap(p, curthread, pc);
new_pc = pc;
@@ -1808,10 +1821,12 @@ done:
rp->r_rip = new_pc;
+#if !defined(sun)
PROC_LOCK(p);
proc_write_regs(curthread, rp);
_PRELE(p);
PROC_UNLOCK(p);
+#endif
return (0);
}
Modified: head/sys/kern/kern_fork.c
==============================================================================
--- head/sys/kern/kern_fork.c Wed Dec 18 01:27:30 2013 (r259534)
+++ head/sys/kern/kern_fork.c Wed Dec 18 01:41:52 2013 (r259535)
@@ -676,12 +676,12 @@ do_fork(struct thread *td, int flags, st
#ifdef KDTRACE_HOOKS
/*
- * Tell the DTrace fasttrap provider about the new process
- * if it has registered an interest. We have to do this only after
- * p_state is PRS_NORMAL since the fasttrap module will use pfind()
- * later on.
+ * Tell the DTrace fasttrap provider about the new process so that any
+ * tracepoints inherited from the parent can be removed. We have to do
+ * this only after p_state is PRS_NORMAL since the fasttrap module will
+ * use pfind() later on.
*/
- if (dtrace_fasttrap_fork)
+ if ((flags & RFMEM) == 0 && dtrace_fasttrap_fork)
dtrace_fasttrap_fork(p1, p2);
#endif
if ((p1->p_flag & (P_TRACED | P_FOLLOWFORK)) == (P_TRACED |
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