tests/fuzz/fuzz.c serves as the entry point for the virtual-device
fuzzer. Namely, libfuzzer invokes the LLVMFuzzerInitialize and
LLVMFuzzerTestOneInput functions, both of which are defined in this
file. This change adds a "FuzzTarget" struct, along with the
fuzz_add_target function, which should be used to define new fuzz
targets.
Signed-off-by: Alexander Bulekov <alx...@bu.edu>
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
---
tests/qtest/fuzz/Makefile.include | 6 +
tests/qtest/fuzz/fuzz.c | 179 ++++++++++++++++++++++++++++++
tests/qtest/fuzz/fuzz.h | 95 ++++++++++++++++
3 files changed, 280 insertions(+)
create mode 100644 tests/qtest/fuzz/Makefile.include
create mode 100644 tests/qtest/fuzz/fuzz.c
create mode 100644 tests/qtest/fuzz/fuzz.h
diff --git a/tests/qtest/fuzz/Makefile.include
b/tests/qtest/fuzz/Makefile.include
new file mode 100644
index 0000000000..8632bb89f4
--- /dev/null
+++ b/tests/qtest/fuzz/Makefile.include
@@ -0,0 +1,6 @@
+QEMU_PROG_FUZZ=qemu-fuzz-$(TARGET_NAME)$(EXESUF)
+
+fuzz-obj-y += tests/qtest/libqtest.o
+fuzz-obj-y += tests/qtest/fuzz/fuzz.o # Fuzzer skeleton
+
+FUZZ_CFLAGS += -I$(SRC_PATH)/tests -I$(SRC_PATH)/tests/qtest
diff --git a/tests/qtest/fuzz/fuzz.c b/tests/qtest/fuzz/fuzz.c
new file mode 100644
index 0000000000..0d78ac8d36
--- /dev/null
+++ b/tests/qtest/fuzz/fuzz.c
@@ -0,0 +1,179 @@
+/*
+ * fuzzing driver
+ *
+ * Copyright Red Hat Inc., 2019
+ *
+ * Authors:
+ * Alexander Bulekov <alx...@bu.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+
+#include <wordexp.h>
+
+#include "sysemu/qtest.h"
+#include "sysemu/runstate.h"
+#include "sysemu/sysemu.h"
+#include "qemu/main-loop.h"
+#include "tests/qtest/libqtest.h"
+#include "tests/qtest/libqos/qgraph.h"
+#include "fuzz.h"
+
+#define MAX_EVENT_LOOPS 10
+
+typedef struct FuzzTargetState {
+ FuzzTarget *target;
+ QSLIST_ENTRY(FuzzTargetState) target_list;
+} FuzzTargetState;
+
+typedef QSLIST_HEAD(, FuzzTargetState) FuzzTargetList;
+
+static const char *fuzz_arch = TARGET_NAME;
+
+static FuzzTargetList *fuzz_target_list;
+static FuzzTarget *fuzz_target;
+static QTestState *fuzz_qts;
+
+
+
+void flush_events(QTestState *s)
+{
+ int i = MAX_EVENT_LOOPS;
+ while (g_main_context_pending(NULL) && i-- > 0) {
+ main_loop_wait(false);
+ }
+}
+
+static QTestState *qtest_setup(void)
+{
+ qtest_server_set_send_handler(&qtest_client_inproc_recv, &fuzz_qts);
+ return qtest_inproc_init(&fuzz_qts, false, fuzz_arch,
+ &qtest_server_inproc_recv);
+}
+
+void fuzz_add_target(const FuzzTarget *target)
+{
+ FuzzTargetState *tmp;
+ FuzzTargetState *target_state;
+ if (!fuzz_target_list) {
+ fuzz_target_list = g_new0(FuzzTargetList, 1);
+ }
+
+ QSLIST_FOREACH(tmp, fuzz_target_list, target_list) {
+ if (g_strcmp0(tmp->target->name, target->name) == 0) {
+ fprintf(stderr, "Error: Fuzz target name %s already in use\n",
+ target->name);
+ abort();
+ }
+ }
+ target_state = g_new0(FuzzTargetState, 1);
+ target_state->target = g_new0(FuzzTarget, 1);
+ *(target_state->target) = *target;
+ QSLIST_INSERT_HEAD(fuzz_target_list, target_state, target_list);
+}
+
+
+
+static void usage(char *path)
+{
+ printf("Usage: %s --fuzz-target=FUZZ_TARGET [LIBFUZZER ARGUMENTS]\n",
path);
+ printf("where FUZZ_TARGET is one of:\n");
+ FuzzTargetState *tmp;
+ if (!fuzz_target_list) {
+ fprintf(stderr, "Fuzz target list not initialized\n");
+ abort();
+ }
+ QSLIST_FOREACH(tmp, fuzz_target_list, target_list) {
+ printf(" * %s : %s\n", tmp->target->name,
+ tmp->target->description);
+ }
+ exit(0);
+}
+
+static FuzzTarget *fuzz_get_target(char* name)
+{
+ FuzzTargetState *tmp;
+ if (!fuzz_target_list) {
+ fprintf(stderr, "Fuzz target list not initialized\n");
+ abort();
+ }
+
+ QSLIST_FOREACH(tmp, fuzz_target_list, target_list) {
+ if (strcmp(tmp->target->name, name) == 0) {
+ return tmp->target;
+ }
+ }
+ return NULL;
+}
+
+
+/* Executed for each fuzzing-input */
+int LLVMFuzzerTestOneInput(const unsigned char *Data, size_t Size)
+{
+ /*
+ * Do the pre-fuzz-initialization before the first fuzzing iteration,
+ * instead of before the actual fuzz loop. This is needed since libfuzzer
+ * may fork off additional workers, prior to the fuzzing loop, and if
+ * pre_fuzz() sets up e.g. shared memory, this should be done for the
+ * individual worker processes
+ */
+ static int pre_fuzz_done;
+ if (!pre_fuzz_done && fuzz_target->pre_fuzz) {
+ fuzz_target->pre_fuzz(fuzz_qts);
+ pre_fuzz_done = true;
+ }
+
+ fuzz_target->fuzz(fuzz_qts, Data, Size);
+ return 0;
+}
+
+/* Executed once, prior to fuzzing */
+int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp)
+{
+
+ char *target_name;
+
+ /* Initialize qgraph and modules */
+ qos_graph_init();
+ module_call_init(MODULE_INIT_FUZZ_TARGET);
+ module_call_init(MODULE_INIT_QOM);
+ module_call_init(MODULE_INIT_LIBQOS);
+
+ if (*argc <= 1) {
+ usage(**argv);
+ }
+
+ /* Identify the fuzz target */
+ target_name = (*argv)[1];
+ if (!strstr(target_name, "--fuzz-target=")) {
+ usage(**argv);
+ }
+
+ target_name += strlen("--fuzz-target=");
+
+ fuzz_target = fuzz_get_target(target_name);
+ if (!fuzz_target) {
+ usage(**argv);
+ }
+
+ fuzz_qts = qtest_setup();
+
+ if (fuzz_target->pre_vm_init) {
+ fuzz_target->pre_vm_init();
+ }
+
+ /* Run QEMU's softmmu main with the fuzz-target dependent arguments */
+ const char *init_cmdline = fuzz_target->get_init_cmdline(fuzz_target);
+
+ /* Split the runcmd into an argv and argc */
+ wordexp_t result;
+ wordexp(init_cmdline, &result, 0);
+
+ qemu_init(result.we_wordc, result.we_wordv, NULL);
+
+ return 0;
+}
diff --git a/tests/qtest/fuzz/fuzz.h b/tests/qtest/fuzz/fuzz.h
new file mode 100644
index 0000000000..03901d414e
--- /dev/null
+++ b/tests/qtest/fuzz/fuzz.h
@@ -0,0 +1,95 @@
+/*
+ * fuzzing driver
+ *
+ * Copyright Red Hat Inc., 2019
+ *
+ * Authors:
+ * Alexander Bulekov <alx...@bu.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef FUZZER_H_
+#define FUZZER_H_
+
+#include "qemu/osdep.h"
+#include "qemu/units.h"
+#include "qapi/error.h"
+
+#include "tests/qtest/libqtest.h"
+
+/**
+ * A libfuzzer fuzzing target
+ *
+ * The QEMU fuzzing binary is built with all available targets, each
+ * with a unique @name that can be specified on the command-line to
+ * select which target should run.
+ *
+ * A target must implement ->fuzz() to process a random input. If QEMU
+ * crashes in ->fuzz() then libfuzzer will record a failure.
+ *
+ * Fuzzing targets are registered with fuzz_add_target():
+ *
+ * static const FuzzTarget fuzz_target = {
+ * .name = "my-device-fifo",
+ * .description = "Fuzz the FIFO buffer registers of my-device",
+ * ...
+ * };
+ *
+ * static void register_fuzz_target(void)
+ * {
+ * fuzz_add_target(&fuzz_target);
+ * }
+ * fuzz_target_init(register_fuzz_target);
+ */
+typedef struct FuzzTarget {
+ const char *name; /* target identifier (passed to --fuzz-target=)*/
+ const char *description; /* help text */
+
+
+ /*
+ * returns the arg-list that is passed to qemu/softmmu init()
+ * Cannot be NULL
+ */
+ const char* (*get_init_cmdline)(struct FuzzTarget *);
+
+ /*
+ * will run once, prior to running qemu/softmmu init.
+ * eg: set up shared-memory for communication with the child-process
+ * Can be NULL
+ */
+ void(*pre_vm_init)(void);
+
+ /*
+ * will run once, after QEMU has been initialized, prior to the fuzz-loop.
+ * eg: detect the memory map
+ * Can be NULL
+ */
+ void(*pre_fuzz)(QTestState *);
+
+ /*
+ * accepts and executes an input from libfuzzer. this is repeatedly
+ * executed during the fuzzing loop. Its should handle setup, input
+ * execution and cleanup.
+ * Cannot be NULL
+ */
+ void(*fuzz)(QTestState *, const unsigned char *, size_t);
+
+} FuzzTarget;
+
+void flush_events(QTestState *);
+void reboot(QTestState *);
+
+/*
+ * makes a copy of *target and adds it to the target-list.
+ * i.e. fine to set up target on the caller's stack
+ */
+void fuzz_add_target(const FuzzTarget *target);
+
+int LLVMFuzzerTestOneInput(const unsigned char *Data, size_t Size);
+int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp);
+
+#endif
+
--
2.23.0
