From 2f948b92316e30c5e19f413b863387dbb2de2451 Mon Sep 17 00:00:00 2001
From: "Dmitry V. Levin" <ldv@altlinux.org>
Date: Sat, 26 Nov 2016 23:45:05 +0000
Subject: [PATCH] Set PTRACE_O_TRACEEXIT option and handle PTRACE_EVENT_EXIT
 events

Do not assume that some syscalls do not generate syscall-exit-stops.
When syscalls fail for any reason they may generate syscall-exit-stops.

The solution is to wait for an actual exit reported by PTRACE_EVENT_EXIT
and print the end of unfinished exiting syscall properly.

* exit.c: Remove.
* Makefile.am (strace_SOURCES): Remove exit.c.
* linux/dummy.h (sys_exit): Alias to printargs_d.
* strace.c (ptrace_setoptions): Add PTRACE_O_TRACEEXIT bit.
(print_event_exit): New function.
(trace): Use it in case of PTRACE_EVENT_EXIT.
* syscall.c (trace_syscall_entering): Remove special handling
of SEN_exit.
---
 Makefile.am   |  1 -
 exit.c        | 15 --------------
 linux/dummy.h |  1 +
 strace.c      | 55 +++++++++++++++++++++++++++++++++++++++++++++------
 syscall.c     |  2 +-
 5 files changed, 51 insertions(+), 23 deletions(-)
 delete mode 100644 exit.c

diff --git a/Makefile.am b/Makefile.am
index 97276f12..80e80fcc 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -104,7 +104,6 @@ strace_SOURCES =	\
 	evdev.c		\
 	eventfd.c	\
 	execve.c	\
-	exit.c		\
 	fadvise.c	\
 	fallocate.c	\
 	fanotify.c	\
diff --git a/exit.c b/exit.c
deleted file mode 100644
index b10f90c2..00000000
--- a/exit.c
+++ /dev/null
@@ -1,15 +0,0 @@
-#include "defs.h"
-
-SYS_FUNC(exit)
-{
-	if (exiting(tcp)) {
-		error_msg("%s returned!", tcp->s_ent->sys_name);
-		return -1;
-	}
-	/* special case: we stop tracing this process, finish line now */
-	tprintf("%ld) ", tcp->u_arg[0]);
-	tabto();
-	tprints("= ?\n");
-	line_ended();
-	return 0;
-}
diff --git a/linux/dummy.h b/linux/dummy.h
index 49dcf16a..4cb9ad46 100644
--- a/linux/dummy.h
+++ b/linux/dummy.h
@@ -123,6 +123,7 @@
 #define	sys_alarm		printargs_u
 
 /* printargs_d does the right thing */
+#define	sys_exit		printargs_d
 #define	sys_getpgid		printargs_d
 #define	sys_getsid		printargs_d
 #define	sys_nice		printargs_d
diff --git a/strace.c b/strace.c
index 95e9d143..5e081ab4 100644
--- a/strace.c
+++ b/strace.c
@@ -80,7 +80,8 @@ const unsigned int syscall_trap_sig = SIGTRAP | 0x80;
 
 cflag_t cflag = CFLAG_NONE;
 unsigned int followfork = 0;
-unsigned int ptrace_setoptions = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC;
+unsigned int ptrace_setoptions = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC
+				 | PTRACE_O_TRACEEXIT;
 unsigned int xflag = 0;
 bool debug_flag = 0;
 bool Tflag = 0;
@@ -2158,6 +2159,43 @@ startup_tcb(struct tcb *tcp)
 	}
 }
 
+static void
+print_event_exit(struct tcb *tcp)
+{
+	if (entering(tcp) || filtered(tcp) || hide_log(tcp)
+	    || cflag == CFLAG_ONLY_STATS) {
+		return;
+	}
+
+	if (followfork < 2 && printing_tcp && printing_tcp != tcp
+	    && printing_tcp->curcol != 0) {
+		current_tcp = printing_tcp;
+		tprints(" <unfinished ...>\n");
+		fflush(printing_tcp->outf);
+		printing_tcp->curcol = 0;
+		current_tcp = tcp;
+	}
+
+	if ((followfork < 2 && printing_tcp != tcp)
+	    || (tcp->flags & TCB_REPRINT)) {
+		tcp->flags &= ~TCB_REPRINT;
+		printleader(tcp);
+		tprintf("<... %s resumed>", tcp->s_ent->sys_name);
+	}
+
+	if (!(tcp->sys_func_rval & RVAL_DECODED)) {
+		/*
+		 * The decoder has probably decided to print something
+		 * on exiting syscall which is not going to happen.
+		 */
+		tprints(" <unfinished ...>");
+	}
+	tprints(") ");
+	tabto();
+	tprints("= ?\n");
+	line_ended();
+}
+
 /* Returns true iff the main trace loop has to continue. */
 static bool
 trace(void)
@@ -2308,10 +2346,14 @@ trace(void)
 
 	sig = WSTOPSIG(status);
 
-	if (event != 0) {
-		/* Ptrace event */
+	switch (event) {
+		case 0:
+			break;
+		case PTRACE_EVENT_EXIT:
+			print_event_exit(tcp);
+			goto restart_tracee_with_sig_0;
 #if USE_SEIZE
-		if (event == PTRACE_EVENT_STOP) {
+		case PTRACE_EVENT_STOP:
 			/*
 			 * PTRACE_INTERRUPT-stop or group-stop.
 			 * PTRACE_INTERRUPT-stop has sig == SIGTRAP here.
@@ -2324,9 +2366,10 @@ trace(void)
 					stopped = true;
 					goto show_stopsig;
 			}
-		}
+			/* fall through */
 #endif
-		goto restart_tracee_with_sig_0;
+		default:
+			goto restart_tracee_with_sig_0;
 	}
 
 	/*
diff --git a/syscall.c b/syscall.c
index e5ab44a5..12962e2c 100644
--- a/syscall.c
+++ b/syscall.c
@@ -1148,7 +1148,7 @@ trace_syscall_entering(struct tcb *tcp)
 
 	printleader(tcp);
 	tprintf("%s(", tcp->s_ent->sys_name);
-	if ((tcp->qual_flg & QUAL_RAW) && SEN_exit != tcp->s_ent->sen)
+	if (tcp->qual_flg & QUAL_RAW)
 		res = printargs(tcp);
 	else
 		res = tcp->s_ent->sys_func(tcp);
-- 
2.40.0