Fix struct sigevent decoding for musl

Do not rely on "struct sigevent.__pad" being located at the same address
as "struct sigevent.sigev_notify_thread_id", it's not the case with musl
libc.  Do not rely on struct sigevent definition at all to access
sigev_notify_thread_id.

* configure.ac (AC_CHECK_MEMBERS): Remove struct sigevent._sigev_un._pad
and struct sigevent.__pad.
* sigevent.h: New file.
* Makefile.am (strace_SOURCES): Add it.
* print_sigevent.c: Include it.
* print_sigevent.c (struct_sigevent): Remove.
(print_sigevent): Update all struct_sigevent users.
* tests/timer_create.c: Include "sigevent.h".
(main): Use struct_sigevent instead of struct sigevent,
all struct sigevent clients changed.

Author: ldv-alt

Makefile.am

@@ -1,7 +1,7 @@
 # Automake input for strace.
 #
 # Copyright (c) 2002-2009 Roland McGrath <[email protected]>
-# Copyright (c) 2006-2015 Dmitry V. Levin <[email protected]>
+# Copyright (c) 2006-2016 Dmitry V. Levin <[email protected]>
 # Copyright (c) 2008-2015 Mike Frysinger <[email protected]>
 # Copyright (c) 2015 Elvira Khabirova <[email protected]>
 # All rights reserved.
@@ -172,6 +172,7 @@ strace_SOURCES =	\
 	seccomp_fprog.h \
 	sendfile.c	\
 	sigaltstack.c	\
+	sigevent.h	\
 	signal.c	\
 	signalfd.c	\
 	sigreturn.c	\

configure.ac

@@ -378,9 +378,7 @@ AC_CHECK_TYPES([struct pt_all_user_regs, struct ia64_fpreg, struct ptrace_peeksi
 
 AC_CHECK_MEMBERS([struct utsname.domainname],,, [#include <sys/utsname.h>])
 
-AC_CHECK_MEMBERS([struct sigevent._sigev_un._pad,
-		  struct sigevent.__pad,
-		  siginfo_t.si_syscall,
+AC_CHECK_MEMBERS([siginfo_t.si_syscall,
 		  siginfo_t.si_timerid,
 		  siginfo_t.si_overrun],,, [#include <signal.h>])
 

print_sigevent.c

@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2003, 2004 Ulrich Drepper <[email protected]>
- * Copyright (c) 2005-2015 Dmitry V. Levin <[email protected]>
+ * Copyright (c) 2005-2016 Dmitry V. Levin <[email protected]>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -29,12 +29,10 @@
 #include "defs.h"
 
 #include DEF_MPERS_TYPE(struct_sigevent)
-
-#include <signal.h>
-typedef struct sigevent struct_sigevent;
-
+#include "sigevent.h"
 #include MPERS_DEFS
 
+#include <signal.h>
 #include "xlat/sigev_value.h"
 
 MPERS_PRINTER_DECL(void, print_sigevent)(struct tcb *tcp, const long addr)
@@ -66,30 +64,13 @@ MPERS_PRINTER_DECL(void, print_sigevent)(struct tcb *tcp, const long addr)
 
 	switch (sev.sigev_notify) {
 	case SIGEV_THREAD_ID:
-#ifndef sigev_notify_thread_id
-		/*
-		 * _pad[0] is the _tid field which might not be
-		 * present in the userlevel definition of the struct.
-		 */
-# if defined HAVE_STRUCT_SIGEVENT__SIGEV_UN__PAD
-#  define sigev_notify_thread_id _sigev_un._pad[0]
-# elif defined HAVE_STRUCT_SIGEVENT___PAD
-#  define sigev_notify_thread_id __pad[0]
-# endif
-#endif
-
-#ifdef sigev_notify_thread_id
-		tprintf(", sigev_notify_thread_id=%d",
-			sev.sigev_notify_thread_id);
-#else
-# warning unfamiliar struct sigevent => incomplete SIGEV_THREAD_ID decoding
-#endif
+		tprintf(", sigev_notify_thread_id=%d", sev.sigev_un.tid);
 		break;
 	case SIGEV_THREAD:
 		tprints(", sigev_notify_function=");
-		printaddr((unsigned long) sev.sigev_notify_function);
+		printaddr(sev.sigev_un.sigev_thread.function);
 		tprints(", sigev_notify_attributes=");
-		printaddr((unsigned long) sev.sigev_notify_attributes);
+		printaddr(sev.sigev_un.sigev_thread.attribute);
 		break;
 	}
 	tprints("}");

sigevent.h

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2016 Dmitry V. Levin <[email protected]>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef SIGEVENT_H_
+#define SIGEVENT_H_
+
+typedef struct {
+	union {
+		int sival_int;
+		unsigned long sival_ptr;
+	} sigev_value;
+	int sigev_signo;
+	int sigev_notify;
+	union {
+		int tid;
+		struct {
+			unsigned long function;
+			unsigned long attribute;
+		} sigev_thread;
+	} sigev_un;
+} struct_sigevent;
+
+#endif

tests/timer_create.c

@@ -34,21 +34,21 @@
 # include <signal.h>
 # include <time.h>
 # include <unistd.h>
+# include "sigevent.h"
 
 int
 main(void)
 {
 	int tid[4] = {};
-	struct sigevent sev = {
+	struct_sigevent sev = {
 		.sigev_notify = SIGEV_NONE,
 		.sigev_signo = 0xfacefeed,
-		.sigev_value.sival_ptr =
-			(void *) (unsigned long) 0xdeadbeefbadc0ded
+		.sigev_value.sival_ptr = (unsigned long) 0xdeadbeefbadc0ded
 	};
 
 	if (syscall(__NR_timer_create, CLOCK_REALTIME, &sev, &tid[0]))
 		perror_msg_and_skip("timer_create CLOCK_REALTIME");
-	printf("timer_create(CLOCK_REALTIME, {sigev_value={int=%d, ptr=%p}"
+	printf("timer_create(CLOCK_REALTIME, {sigev_value={int=%d, ptr=%#lx}"
 	       ", sigev_signo=%u, sigev_notify=SIGEV_NONE}"
 	       ", [%d]) = 0\n",
 	       sev.sigev_value.sival_int,
@@ -59,54 +59,42 @@ main(void)
 	sev.sigev_signo = SIGALRM;
 	if (syscall(__NR_timer_create, CLOCK_MONOTONIC, &sev, &tid[1]))
 		perror_msg_and_skip("timer_create CLOCK_MONOTONIC");
-	printf("timer_create(CLOCK_MONOTONIC, {sigev_value={int=%d, ptr=%p}"
+	printf("timer_create(CLOCK_MONOTONIC, {sigev_value={int=%d, ptr=%#lx}"
 	       ", sigev_signo=SIGALRM, sigev_notify=SIGEV_SIGNAL}"
 	       ", [%d]) = 0\n",
 	       sev.sigev_value.sival_int,
 	       sev.sigev_value.sival_ptr, tid[1]);
 
 	sev.sigev_notify = SIGEV_THREAD;
-	sev.sigev_notify_function =
-		(void *) (unsigned long) 0xdeadbeefbadc0ded;
-	sev.sigev_notify_attributes =
-		(void *) (unsigned long) 0xcafef00dfacefeed;
+	sev.sigev_un.sigev_thread.function = (unsigned long) 0xdeadbeefbadc0ded;
+	sev.sigev_un.sigev_thread.attribute = (unsigned long) 0xcafef00dfacefeed;
 	if (syscall(__NR_timer_create, CLOCK_REALTIME, &sev, &tid[2]))
 		perror_msg_and_skip("timer_create CLOCK_REALTIME");
-	printf("timer_create(CLOCK_REALTIME, {sigev_value={int=%d, ptr=%p}"
+	printf("timer_create(CLOCK_REALTIME, {sigev_value={int=%d, ptr=%#lx}"
 	       ", sigev_signo=SIGALRM, sigev_notify=SIGEV_THREAD"
-	       ", sigev_notify_function=%p, sigev_notify_attributes=%p}"
+	       ", sigev_notify_function=%#lx, sigev_notify_attributes=%#lx}"
 	       ", [%d]) = 0\n",
 	       sev.sigev_value.sival_int,
 	       sev.sigev_value.sival_ptr,
-	       sev.sigev_notify_function,
-	       sev.sigev_notify_attributes,
+	       sev.sigev_un.sigev_thread.function,
+	       sev.sigev_un.sigev_thread.attribute,
 	       tid[2]);
 
-#ifndef sigev_notify_thread_id
-# if defined HAVE_STRUCT_SIGEVENT__SIGEV_UN__PAD
-#  define sigev_notify_thread_id _sigev_un._pad[0]
-# elif defined HAVE_STRUCT_SIGEVENT___PAD
-#  define sigev_notify_thread_id __pad[0]
-# endif
-#endif /* !sigev_notify_thread_id */
-
-#ifdef sigev_notify_thread_id
-# ifndef SIGEV_THREAD_ID
-#  define SIGEV_THREAD_ID 4
-# endif
+#ifndef SIGEV_THREAD_ID
+# define SIGEV_THREAD_ID 4
+#endif
 	sev.sigev_notify = SIGEV_THREAD_ID;
-	sev.sigev_notify_thread_id = getpid();
+	sev.sigev_un.tid = getpid();
 	if (syscall(__NR_timer_create, CLOCK_MONOTONIC, &sev, &tid[3]))
 		perror_msg_and_skip("timer_create CLOCK_MONOTONIC");
-	printf("timer_create(CLOCK_MONOTONIC, {sigev_value={int=%d, ptr=%p}"
+	printf("timer_create(CLOCK_MONOTONIC, {sigev_value={int=%d, ptr=%#lx}"
 	       ", sigev_signo=SIGALRM, sigev_notify=SIGEV_THREAD_ID"
 	       ", sigev_notify_thread_id=%d}"
 	       ", [%d]) = 0\n",
 	       sev.sigev_value.sival_int,
 	       sev.sigev_value.sival_ptr,
-	       sev.sigev_notify_thread_id,
+	       sev.sigev_un.tid,
 	       tid[3]);
-#endif /* sigev_notify_thread_id */
 
 	puts("+++ exited with 0 +++");
 	return 0;