Add support for capturing 'struct ptrace_lwpinfo' for signals

resulting in a process dumping core in the corefile.

Also extend procstat to view select members of 'struct ptrace_lwpinfo'
from the contents of the note.

Sponsored by:	Dell EMC Isilon

3 files changed, 61 insertions, 7 deletions

diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c
index ad5c3acf4dd9..dedc3660e172 100644
--- a/sys/kern/imgact_elf.c
+++ b/sys/kern/imgact_elf.c
@@ -1,4 +1,5 @@
 /*-
+ * Copyright (c) 2017 Dell EMC
  * Copyright (c) 2000 David O'Brien
  * Copyright (c) 1995-1996 Søren Schmidt
  * Copyright (c) 1996 Peter Wemm
@@ -52,6 +53,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/pioctl.h>
 #include <sys/proc.h>
 #include <sys/procfs.h>
+#include <sys/ptrace.h>
 #include <sys/racct.h>
 #include <sys/resourcevar.h>
 #include <sys/rwlock.h>
@@ -1202,6 +1204,7 @@ static void __elfN(note_prpsinfo)(void *, struct sbuf *, size_t *);
 static void __elfN(note_prstatus)(void *, struct sbuf *, size_t *);
 static void __elfN(note_threadmd)(void *, struct sbuf *, size_t *);
 static void __elfN(note_thrmisc)(void *, struct sbuf *, size_t *);
+static void __elfN(note_ptlwpinfo)(void *, struct sbuf *, size_t *);
 static void __elfN(note_procstat_auxv)(void *, struct sbuf *, size_t *);
 static void __elfN(note_procstat_proc)(void *, struct sbuf *, size_t *);
 static void __elfN(note_procstat_psstrings)(void *, struct sbuf *, size_t *);
@@ -1628,6 +1631,8 @@ __elfN(prepare_notes)(struct thread *td, struct note_info_list *list,
 		    __elfN(note_fpregset), thr);
 		size += register_note(list, NT_THRMISC,
 		    __elfN(note_thrmisc), thr);
+		size += register_note(list, NT_PTLWPINFO,
+		    __elfN(note_ptlwpinfo), thr);
 		size += register_note(list, -1,
 		    __elfN(note_threadmd), thr);
 
@@ -2018,6 +2023,37 @@ __elfN(note_thrmisc)(void *arg, struct sbuf *sb, size_t *sizep)
 	*sizep = sizeof(thrmisc);
 }
 
+static void
+__elfN(note_ptlwpinfo)(void *arg, struct sbuf *sb, size_t *sizep)
+{
+	struct thread *td;
+	size_t size;
+	int structsize;
+	struct ptrace_lwpinfo pl;
+
+	td = (struct thread *)arg;
+	size = sizeof(structsize) + sizeof(struct ptrace_lwpinfo);
+	if (sb != NULL) {
+		KASSERT(*sizep == size, ("invalid size"));
+		structsize = sizeof(struct ptrace_lwpinfo);
+		sbuf_bcat(sb, &structsize, sizeof(structsize));
+		bzero(&pl, sizeof(pl));
+		pl.pl_lwpid = td->td_tid;
+		pl.pl_event = PL_EVENT_NONE;
+		pl.pl_sigmask = td->td_sigmask;
+		pl.pl_siglist = td->td_siglist;
+		if (td->td_si.si_signo != 0) {
+			pl.pl_event = PL_EVENT_SIGNAL;
+			pl.pl_flags |= PL_FLAG_SI;
+			pl.pl_siginfo = td->td_si;
+		}
+		strcpy(pl.pl_tdname, td->td_name);
+		/* XXX TODO: supply more information in struct ptrace_lwpinfo*/
+		sbuf_bcat(sb, &pl, sizeof(struct ptrace_lwpinfo));
+	}
+	*sizep = size;
+}
+
 /*
  * Allow for MD specific notes, as well as any MD
  * specific preparations for writing MI notes.
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 6f102ceb6c68..e43cd6b8482f 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -1226,6 +1226,19 @@ sys_sigwaitinfo(struct thread *td, struct sigwaitinfo_args *uap)
 	return (error);
 }
 
+static void
+proc_td_siginfo_capture(struct thread *td, siginfo_t *si)
+{
+	struct thread *thr;
+
+	FOREACH_THREAD_IN_PROC(td->td_proc, thr) {
+		if (thr == td)
+			thr->td_si = *si;
+		else
+			thr->td_si.si_signo = 0;
+	}
+}
+
 int
 kern_sigtimedwait(struct thread *td, sigset_t waitset, ksiginfo_t *ksi,
 	struct timespec *timeout)
@@ -1334,8 +1347,10 @@ kern_sigtimedwait(struct thread *td, sigset_t waitset, ksiginfo_t *ksi,
 			ktrpsig(sig, action, &td->td_sigmask, ksi->ksi_code);
 		}
 #endif
-		if (sig == SIGKILL)
+		if (sig == SIGKILL) {
+			proc_td_siginfo_capture(td, &ksi->ksi_info);
 			sigexit(td, sig);
+		}
 	}
 	PROC_UNLOCK(p);
 	return (error);
@@ -2756,6 +2771,7 @@ issignal(struct thread *td)
 	struct sigqueue *queue;
 	sigset_t sigpending;
 	int sig, prop;
+	ksiginfo_t ksi;
 
 	p = td->td_proc;
 	ps = p->p_sigacts;
@@ -2811,14 +2827,15 @@ issignal(struct thread *td)
 			 * be thrown away.
 			 */
 			queue = &td->td_sigqueue;
-			td->td_dbgksi.ksi_signo = 0;
-			if (sigqueue_get(queue, sig, &td->td_dbgksi) == 0) {
+			ksiginfo_init(&ksi);
+			if (sigqueue_get(queue, sig, &ksi) == 0) {
 				queue = &p->p_sigqueue;
-				sigqueue_get(queue, sig, &td->td_dbgksi);
+				sigqueue_get(queue, sig, &ksi);
 			}
+			td->td_si = ksi.ksi_info;
 
 			mtx_unlock(&ps->ps_mtx);
-			sig = ptracestop(td, sig, &td->td_dbgksi);
+			sig = ptracestop(td, sig, &ksi);
 			mtx_lock(&ps->ps_mtx);
 
 			/* 
@@ -2989,6 +3006,7 @@ postsig(sig)
 		 * the process.  (Other cases were ignored above.)
 		 */
 		mtx_unlock(&ps->ps_mtx);
+		proc_td_siginfo_capture(td, &ksi.ksi_info);
 		sigexit(td, sig);
 		/* NOTREACHED */
 	} else {
diff --git a/sys/kern/sys_process.c b/sys/kern/sys_process.c
index ded874ac9819..7bb167a14ef2 100644
--- a/sys/kern/sys_process.c
+++ b/sys/kern/sys_process.c
@@ -1306,7 +1306,7 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
 		pl->pl_flags = 0;
 		if (td2->td_dbgflags & TDB_XSIG) {
 			pl->pl_event = PL_EVENT_SIGNAL;
-			if (td2->td_dbgksi.ksi_signo != 0 &&
+			if (td2->td_si.si_signo != 0 &&
 #ifdef COMPAT_FREEBSD32
 			    ((!wrap32 && data >= offsetof(struct ptrace_lwpinfo,
 			    pl_siginfo) + sizeof(pl->pl_siginfo)) ||
@@ -1318,7 +1318,7 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
 #endif
 			){
 				pl->pl_flags |= PL_FLAG_SI;
-				pl->pl_siginfo = td2->td_dbgksi.ksi_info;
+				pl->pl_siginfo = td2->td_si;
 			}
 		}
 		if ((pl->pl_flags & PL_FLAG_SI) == 0)