Add test reproducing ASAN-like hangs

Backtraces suggest that AddressSanitizer replaces malloc() with a
function that

- locks a mutex and
- calls clock_gettime() while the mutex is held

This commit adds a test that implements a trivial malloc() that behaves
similarly. Currently, this test hangs.

Signed-off-by: Uli Schlachter <psychon@znc.in>

test/Makefile

@@ -26,7 +26,7 @@ all: $(ALL_TESTS)
 timetest: ${OBJ}
 	${CC} -o $@ ${OBJ} ${LDFLAGS}
 
-test: timetest functest
+test: timetest functest libmallocintercept.so
 	@echo
 	@./test.sh
 
@@ -40,6 +40,9 @@ functest:
 randomtest: repeat_random
 	./randomtest.sh
 
+libmallocintercept.so: libmallocintercept.c
+	${CC} -shared -o $@ -fpic ${CFLAGS} $<
+
 # ensure our variadic argument unpacking/repacking works as expected
 confirm_variadic_promotion: variadic_promotion
 	./variadic_promotion

test/libmallocintercept.c

@@ -0,0 +1,79 @@
+/*
+ *  Copyright (C) 2022 be.storaged GmbH
+ *
+ *  This file is part of libfaketime
+ *
+ *  libfaketime is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License v2 as published by the
+ *  Free Software Foundation.
+ *
+ *  libfaketime is distributed in the hope that it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ *  more details.
+ *
+ *  You should have received a copy of the GNU General Public License v2 along
+ *  with the libfaketime; if not, write to the Free Software Foundation,
+ *  Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <pthread.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+static void print_msg(const char *msg) {
+	write(0, msg, strlen(msg));
+}
+
+static void* actual_malloc(size_t size) {
+	/* We would like to use "the real malloc", but cannot. Thus, this
+	 * implements a trivial, allocate-only bump allocator to make things
+	 * work.
+	 */
+	static char memory_arena[16 << 20];
+	static size_t allocated_index = 0;
+
+	void *result = &memory_arena[allocated_index];
+
+	allocated_index += size;
+	/* align to a multiple of 8 bytes */
+	allocated_index = (allocated_index + 7) / 8 * 8;
+
+	if (allocated_index >= sizeof(memory_arena)) {
+		print_msg("libmallocintercept is out of memory!");
+		abort();
+	}
+
+	return result;
+}
+
+static void poke_faketime(void) {
+	/* To complicate things for libfaketime, this calls clock_gettime()
+	 * while holding a lock. This should simulate problems that occurred
+	 * with address sanitizer.
+	 */
+	static pthread_mutex_t time_mutex = PTHREAD_MUTEX_INITIALIZER;
+	struct timespec timespec;
+
+	pthread_mutex_lock(&time_mutex);
+	clock_gettime(CLOCK_REALTIME, &timespec);
+	pthread_mutex_unlock(&time_mutex);
+}
+
+void *malloc(size_t size) {
+	print_msg("Called malloc() from libmallocintercept...");
+	poke_faketime();
+	print_msg("successfully\n");
+	return actual_malloc(size);
+}
+
+void free(void *) {
+	print_msg("Called free() from libmallocintercept...");
+	poke_faketime();
+	print_msg("successfully\n");
+
+	/* We cannot actually free memory */
+}
+

test/test.sh

@@ -1,6 +1,7 @@
 #!/bin/sh
 
 FTPL="${FAKETIME_TESTLIB:-../src/libfaketime.so.1}"
+MALLOC_INTERCEPT=./libmallocintercept.so
 
 if [ -f /etc/faketimerc ] ; then
 	echo "Running the test program with your system-wide default in /etc/faketimerc"
@@ -62,6 +63,14 @@ echo "\$ LD_PRELOAD=$FTPL FAKETIME=\"-15d\" date"
 LD_PRELOAD="$FTPL" FAKETIME="-15d" date
 echo
 
+echo "============================================================================="
+echo
+
+echo "Running the test program with malloc interception"
+echo "\$ LD_PRELOAD=./libmallocintercept.so:$FTPL ./timetest"
+LD_PRELOAD="./libmallocintercept.so:$FTPL" ./timetest
+echo
+
 echo "============================================================================="
 echo "Testing finished."