From 7159310fa68979b45de779f0e49522d3262eb0a4 Mon Sep 17 00:00:00 2001 From: Mark Johnston Date: Wed, 18 Dec 2013 01:41:52 +0000 Subject: [PATCH] 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 --- .../uts/intel/dtrace/fasttrap_isa.c | 33 ++++++++++++++----- sys/kern/kern_fork.c | 10 +++--- 2 files changed, 29 insertions(+), 14 deletions(-) diff --git a/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c b/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c index c803a01a79f4..53ad33b39cf1 100644 --- a/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c +++ b/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c @@ -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 + + pid = p->p_pid; + 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); - pid = p->p_pid; -#if defined(sun) - pid_mtx = &cpu_core[CPU->cpu_id].cpuc_pid_lock; - mutex_enter(pid_mtx); #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 @@ fasttrap_pid_probe(struct reg *rp) rp->r_rip = new_pc; +#if !defined(sun) PROC_LOCK(p); proc_write_regs(curthread, rp); _PRELE(p); PROC_UNLOCK(p); +#endif return (0); } diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c index 3198bd5938be..b3d9c243f942 100644 --- a/sys/kern/kern_fork.c +++ b/sys/kern/kern_fork.c @@ -676,12 +676,12 @@ do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2, #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 |