Date: Fri, 9 Nov 2018 17:43:23 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r340290 - stable/11/sys/kern Message-ID: <201811091743.wA9HhNYD004383@repo.freebsd.org>
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Author: kib Date: Fri Nov 9 17:43:23 2018 New Revision: 340290 URL: https://svnweb.freebsd.org/changeset/base/340290 Log: MFC r325771, r325777, r325778 (all by jhb): Only clear a pending thread event if one is pending. This fixes a panic when attaching to an already-stopped process. Also do some other clean ups for control flow of sendsig section. Reviewed by: jhb Sponsored by: The FreeBSD Foundation Modified: stable/11/sys/kern/sys_process.c Directory Properties: stable/11/ (props changed) Modified: stable/11/sys/kern/sys_process.c ============================================================================== --- stable/11/sys/kern/sys_process.c Fri Nov 9 17:43:19 2018 (r340289) +++ stable/11/sys/kern/sys_process.c Fri Nov 9 17:43:23 2018 (r340290) @@ -870,19 +870,13 @@ kern_ptrace(struct thread *td, int req, pid_t pid, voi } /* not currently stopped */ - if ((p->p_flag & (P_STOPPED_SIG | P_STOPPED_TRACE)) == 0 || + if ((p->p_flag & P_STOPPED_TRACE) == 0 || p->p_suspcount != p->p_numthreads || (p->p_flag & P_WAITED) == 0) { error = EBUSY; goto fail; } - if ((p->p_flag & P_STOPPED_TRACE) == 0) { - static int count = 0; - if (count++ == 0) - printf("P_STOPPED_TRACE not set.\n"); - } - /* OK */ break; } @@ -927,11 +921,28 @@ kern_ptrace(struct thread *td, int req, pid_t pid, voi if (p->p_pptr != td->td_proc) { proc_reparent(p, td->td_proc); } - data = SIGSTOP; CTR2(KTR_PTRACE, "PT_ATTACH: pid %d, oppid %d", p->p_pid, p->p_oppid); - goto sendsig; /* in PT_CONTINUE below */ + sx_xunlock(&proctree_lock); + proctree_locked = 0; + MPASS(p->p_xthread == NULL); + MPASS((p->p_flag & P_STOPPED_TRACE) == 0); + + /* + * If already stopped due to a stop signal, clear the + * existing stop before triggering a traced SIGSTOP. + */ + if ((p->p_flag & P_STOPPED_SIG) != 0) { + PROC_SLOCK(p); + p->p_flag &= ~(P_STOPPED_SIG | P_WAITED); + thread_unsuspend(p); + PROC_SUNLOCK(p); + } + + kern_psignal(p, SIGSTOP); + break; + case PT_CLEARSTEP: CTR2(KTR_PTRACE, "PT_CLEARSTEP: tid %d (pid %d)", td2->td_tid, p->p_pid); @@ -1118,8 +1129,10 @@ kern_ptrace(struct thread *td, int req, pid_t pid, voi sigqueue_delete(&td3->td_sigqueue, SIGSTOP); } - td3->td_dbgflags &= ~(TDB_XSIG | TDB_FSTP); + td3->td_dbgflags &= ~(TDB_XSIG | TDB_FSTP | + TDB_SUSPEND); } + if ((p->p_flag2 & P2_PTRACE_FSTP) != 0) { sigqueue_delete(&p->p_sigqueue, SIGSTOP); p->p_flag2 &= ~P2_PTRACE_FSTP; @@ -1130,54 +1143,45 @@ kern_ptrace(struct thread *td, int req, pid_t pid, voi break; } + sx_xunlock(&proctree_lock); + proctree_locked = 0; + sendsig: - /* + MPASS(proctree_locked == 0); + + /* * Clear the pending event for the thread that just * reported its event (p_xthread). This may not be * the thread passed to PT_CONTINUE, PT_STEP, etc. if * the debugger is resuming a different thread. + * + * Deliver any pending signal via the reporting thread. */ - td2 = p->p_xthread; - if (proctree_locked) { - sx_xunlock(&proctree_lock); - proctree_locked = 0; - } - p->p_xsig = data; + MPASS(p->p_xthread != NULL); + p->p_xthread->td_dbgflags &= ~TDB_XSIG; + p->p_xthread->td_xsig = data; p->p_xthread = NULL; - if ((p->p_flag & (P_STOPPED_SIG | P_STOPPED_TRACE)) != 0) { - /* deliver or queue signal */ - td2->td_dbgflags &= ~TDB_XSIG; - td2->td_xsig = data; + p->p_xsig = data; - /* - * P_WKILLED is insurance that a PT_KILL/SIGKILL always - * works immediately, even if another thread is - * unsuspended first and attempts to handle a different - * signal or if the POSIX.1b style signal queue cannot - * accommodate any new signals. - */ - if (data == SIGKILL) - proc_wkilled(p); + /* + * P_WKILLED is insurance that a PT_KILL/SIGKILL + * always works immediately, even if another thread is + * unsuspended first and attempts to handle a + * different signal or if the POSIX.1b style signal + * queue cannot accommodate any new signals. + */ + if (data == SIGKILL) + proc_wkilled(p); - if (req == PT_DETACH) { - FOREACH_THREAD_IN_PROC(p, td3) - td3->td_dbgflags &= ~TDB_SUSPEND; - } - /* - * unsuspend all threads, to not let a thread run, - * you should use PT_SUSPEND to suspend it before - * continuing process. - */ - PROC_SLOCK(p); - p->p_flag &= ~(P_STOPPED_TRACE|P_STOPPED_SIG|P_WAITED); - thread_unsuspend(p); - PROC_SUNLOCK(p); - if (req == PT_ATTACH) - kern_psignal(p, data); - } else { - if (data) - kern_psignal(p, data); - } + /* + * Unsuspend all threads. To leave a thread + * suspended, use PT_SUSPEND to suspend it before + * continuing the process. + */ + PROC_SLOCK(p); + p->p_flag &= ~(P_STOPPED_TRACE | P_STOPPED_SIG | P_WAITED); + thread_unsuspend(p); + PROC_SUNLOCK(p); break; case PT_WRITE_I:
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