Index: head/lib/libc/sys/ptrace.2 =================================================================== --- head/lib/libc/sys/ptrace.2 +++ head/lib/libc/sys/ptrace.2 @@ -2,7 +2,7 @@ .\" $NetBSD: ptrace.2,v 1.2 1995/02/27 12:35:37 cgd Exp $ .\" .\" This file is in the public domain. -.Dd July 15, 2016 +.Dd July 18, 2016 .Dt PTRACE 2 .Os .Sh NAME @@ -141,6 +141,11 @@ .Va pl_child_pid member of .Vt "struct ptrace_lwpinfo" . +If the new child process was created via +.Xr vfork 2 , +the traced process's stop will also include the +.Dv PL_FLAG_VFORKED +flag. Note that new child processes will be attached with the default tracing event mask; they do not inherit the event mask of the traced process. @@ -163,6 +168,33 @@ initial thread, and exiting processes do not report an event for the termination of the last thread. +.It Dv PTRACE_VFORK +Report a stop event when a parent process resumes after a +.Xr vfork 2 . +.Pp +When a thread in the traced process creates a new child process via +.Xr vfork 2 , +the stop that reports +.Dv PL_FLAG_FORKED +and +.Dv PL_FLAG_SCX +occurs just after the child process is created, +but before the thread waits for the child process to stop sharing process +memory. +If a debugger is not tracing the new child process, +it must ensure that no breakpoints are enabled in the shared process +memory before detaching from the new child process. +This means that no breakpoints are enabled in the parent process either. +.Pp +The +.Dv PTRACE_VFORK +flag enables a new stop that indicates when the new child process stops +sharing the process memory of the parent process. +A debugger can reinsert breakpoints in the parent process and resume it +in response to this event. +This event is indicated by setting the +.Dv PL_FLAG_VFORK_DONE +flag. .El .Pp The default tracing event mask when attaching to a process via @@ -491,6 +523,16 @@ Note that this event is not reported when the last LWP in a process exits. The termination of the last thread is reported via a normal process exit event. +.It PL_FLAG_VFORKED +Indicates that the thread is returning from a call to +.Xr vfork 2 +that created a new child process. +This flag is set in addition to +.Dv PL_FLAG_FORKED . +.It PL_FLAG_VFORK_DONE +Indicates that the thread has resumed after a child process created via +.Xr vfork 2 +has stopped sharing its address space with the traced process. .El .It pl_sigmask The current signal mask of the LWP Index: head/sys/kern/kern_fork.c =================================================================== --- head/sys/kern/kern_fork.c +++ head/sys/kern/kern_fork.c @@ -735,6 +735,7 @@ if (fr->fr_flags & RFPPWAIT) { td->td_pflags |= TDP_RFPPWAIT; td->td_rfppwait_p = p2; + td->td_dbgflags |= TDB_VFORK; } PROC_UNLOCK(p2); Index: head/sys/kern/subr_syscall.c =================================================================== --- head/sys/kern/subr_syscall.c +++ head/sys/kern/subr_syscall.c @@ -242,5 +242,13 @@ cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz); } PROC_UNLOCK(p2); + + if (td->td_dbgflags & TDB_VFORK) { + PROC_LOCK(p); + if (p->p_ptevents & PTRACE_VFORK) + ptracestop(td, SIGTRAP); + td->td_dbgflags &= ~TDB_VFORK; + PROC_UNLOCK(p); + } } } Index: head/sys/kern/sys_process.c =================================================================== --- head/sys/kern/sys_process.c +++ head/sys/kern/sys_process.c @@ -993,7 +993,7 @@ } tmp = *(int *)addr; if ((tmp & ~(PTRACE_EXEC | PTRACE_SCE | PTRACE_SCX | - PTRACE_FORK | PTRACE_LWP)) != 0) { + PTRACE_FORK | PTRACE_LWP | PTRACE_VFORK)) != 0) { error = EINVAL; break; } @@ -1303,7 +1303,11 @@ if (td2->td_dbgflags & TDB_FORK) { pl->pl_flags |= PL_FLAG_FORKED; pl->pl_child_pid = td2->td_dbg_forked; - } + if (td2->td_dbgflags & TDB_VFORK) + pl->pl_flags |= PL_FLAG_VFORKED; + } else if ((td2->td_dbgflags & (TDB_SCX | TDB_VFORK)) == + TDB_VFORK) + pl->pl_flags |= PL_FLAG_VFORK_DONE; if (td2->td_dbgflags & TDB_CHILD) pl->pl_flags |= PL_FLAG_CHILD; if (td2->td_dbgflags & TDB_BORN) Index: head/sys/sys/proc.h =================================================================== --- head/sys/sys/proc.h +++ head/sys/sys/proc.h @@ -422,6 +422,7 @@ #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() */ +#define TDB_VFORK 0x00000800 /* vfork indicator for ptrace() */ /* * "Private" flags kept in td_pflags: Index: head/sys/sys/ptrace.h =================================================================== --- head/sys/sys/ptrace.h +++ head/sys/sys/ptrace.h @@ -89,6 +89,7 @@ #define PTRACE_SYSCALL (PTRACE_SCE | PTRACE_SCX) #define PTRACE_FORK 0x0008 #define PTRACE_LWP 0x0010 +#define PTRACE_VFORK 0x0020 #define PTRACE_DEFAULT (PTRACE_EXEC) @@ -124,6 +125,8 @@ #define PL_FLAG_CHILD 0x80 /* I am from child */ #define PL_FLAG_BORN 0x100 /* new LWP */ #define PL_FLAG_EXITED 0x200 /* exiting LWP */ +#define PL_FLAG_VFORKED 0x400 /* new child via vfork */ +#define PL_FLAG_VFORK_DONE 0x800 /* vfork parent has resumed */ sigset_t pl_sigmask; /* LWP signal mask */ sigset_t pl_siglist; /* LWP pending signal */ struct __siginfo pl_siginfo; /* siginfo for signal */ Index: head/tests/sys/kern/ptrace_test.c =================================================================== --- head/tests/sys/kern/ptrace_test.c +++ head/tests/sys/kern/ptrace_test.c @@ -1549,6 +1549,130 @@ ATF_REQUIRE(errno == ECHILD); } +/* + * Verify that the expected ptrace events are reported for PTRACE_VFORK. + */ +ATF_TC_WITHOUT_HEAD(ptrace__ptrace_vfork); +ATF_TC_BODY(ptrace__ptrace_vfork, tc) +{ + struct ptrace_lwpinfo pl; + pid_t fpid, wpid; + int events, status; + + ATF_REQUIRE((fpid = fork()) != -1); + if (fpid == 0) { + trace_me(); + follow_fork_parent(true); + } + + /* 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_GET_EVENT_MASK, fpid, (caddr_t)&events, + sizeof(events)) == 0); + events |= PTRACE_VFORK; + ATF_REQUIRE(ptrace(PT_SET_EVENT_MASK, fpid, (caddr_t)&events, + sizeof(events)) == 0); + + /* Continue the child ignoring the SIGSTOP. */ + ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) != -1); + + /* The next event should report the end of the vfork. */ + wpid = wait(&status); + 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_VFORK_DONE) != 0); + + ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) != -1); + + wpid = wait(&status); + ATF_REQUIRE(wpid == fpid); + ATF_REQUIRE(WIFEXITED(status)); + ATF_REQUIRE(WEXITSTATUS(status) == 1); + + wpid = wait(&status); + ATF_REQUIRE(wpid == -1); + ATF_REQUIRE(errno == ECHILD); +} + +ATF_TC_WITHOUT_HEAD(ptrace__ptrace_vfork_follow); +ATF_TC_BODY(ptrace__ptrace_vfork_follow, tc) +{ + struct ptrace_lwpinfo pl[2]; + pid_t children[2], fpid, wpid; + int events, status; + + ATF_REQUIRE((fpid = fork()) != -1); + if (fpid == 0) { + trace_me(); + follow_fork_parent(true); + } + + /* Parent process. */ + children[0] = fpid; + + /* The first wait() should report the stop from SIGSTOP. */ + wpid = waitpid(children[0], &status, 0); + ATF_REQUIRE(wpid == children[0]); + ATF_REQUIRE(WIFSTOPPED(status)); + ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP); + + ATF_REQUIRE(ptrace(PT_GET_EVENT_MASK, children[0], (caddr_t)&events, + sizeof(events)) == 0); + events |= PTRACE_FORK | PTRACE_VFORK; + ATF_REQUIRE(ptrace(PT_SET_EVENT_MASK, children[0], (caddr_t)&events, + sizeof(events)) == 0); + + /* Continue the child ignoring the SIGSTOP. */ + ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1); + + /* Wait for both halves of the fork event to get reported. */ + children[1] = handle_fork_events(children[0], pl); + ATF_REQUIRE(children[1] > 0); + + ATF_REQUIRE((pl[0].pl_flags & PL_FLAG_VFORKED) != 0); + + ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1); + ATF_REQUIRE(ptrace(PT_CONTINUE, children[1], (caddr_t)1, 0) != -1); + + /* + * The child can't exit until the grandchild reports status, so the + * grandchild should report its exit first to the debugger. + */ + wpid = waitpid(children[1], &status, 0); + ATF_REQUIRE(wpid == children[1]); + ATF_REQUIRE(WIFEXITED(status)); + ATF_REQUIRE(WEXITSTATUS(status) == 2); + + /* + * The child should report it's vfork() completion before it + * exits. + */ + wpid = wait(&status); + ATF_REQUIRE(wpid == children[0]); + ATF_REQUIRE(WIFSTOPPED(status)); + ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP); + ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl[0], sizeof(pl[0])) != + -1); + ATF_REQUIRE((pl[0].pl_flags & PL_FLAG_VFORK_DONE) != 0); + + ATF_REQUIRE(ptrace(PT_CONTINUE, children[0], (caddr_t)1, 0) != -1); + + wpid = wait(&status); + ATF_REQUIRE(wpid == children[0]); + ATF_REQUIRE(WIFEXITED(status)); + ATF_REQUIRE(WEXITSTATUS(status) == 1); + + wpid = wait(&status); + ATF_REQUIRE(wpid == -1); + ATF_REQUIRE(errno == ECHILD); +} + ATF_TP_ADD_TCS(tp) { @@ -1574,6 +1698,8 @@ ATF_TP_ADD_TC(tp, ptrace__ptrace_exec_disable); ATF_TP_ADD_TC(tp, ptrace__ptrace_exec_enable); ATF_TP_ADD_TC(tp, ptrace__event_mask); + ATF_TP_ADD_TC(tp, ptrace__ptrace_vfork); + ATF_TP_ADD_TC(tp, ptrace__ptrace_vfork_follow); return (atf_no_error()); }