[PATCH v3 3/5] Demonstrating unit testing via simple-harness

Sam Caccavale
2019-06-24T14:25:12Z

Simple-harness.c uses inline asm support to generate asm and then has the
emulator emulate this code. This may be useful as a form of testing for
the emulator.

---

v1 -> v2:
- Accidentally changed the example

V2 -> v3:
- Reverted the example back to the more useful original one

Signed-off-by: Sam Caccavale <samcacc@amazon.de>
---
tools/fuzz/x86ie/Makefile | 7 +++--
tools/fuzz/x86ie/simple-harness.c | 49 +++++++++++++++++++++++++++++++
2 files changed, 54 insertions(+), 2 deletions(-)
create mode 100644 tools/fuzz/x86ie/simple-harness.c

diff --git a/tools/fuzz/x86ie/Makefile b/tools/fuzz/x86ie/Makefile
index d45fe6d266b9..e79d275e1040 100644
--- a/tools/fuzz/x86ie/Makefile
+++ b/tools/fuzz/x86ie/Makefile
@@ -44,8 +44,11 @@ LOCAL_OBJS := emulator_ops.o stubs.o
afl-harness: afl-harness.o $(LOCAL_OBJS) $(KERNEL_OBJS)
@$(CC) -v $(KBUILD_CFLAGS) $(LOCAL_OBJS) $(KERNEL_OBJS) $< $(INCLUDES) -Istubs.h -o $@ -no-pie

-all: afl-harness
+simple-harness: simple-harness.o $(LOCAL_OBJS) $(KERNEL_OBJS)
+ @$(CC) -v $(KBUILD_CFLAGS) $(LOCAL_OBJS) $(KERNEL_OBJS) $< $(INCLUDES) -Istubs.h -o $@ -no-pie
+
+all: afl-harness simple-harness

.PHONY: clean
clean:
- $(RM) -r *.o afl-harness
+ $(RM) -r *.o afl-harness simple-harness
diff --git a/tools/fuzz/x86ie/simple-harness.c b/tools/fuzz/x86ie/simple-harness.c
new file mode 100644
index 000000000000..9601aafb9423
--- /dev/null
+++ b/tools/fuzz/x86ie/simple-harness.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include "emulator_ops.h"
+#include <asm/kvm_emulate.h>
+
+extern void foo(void)
+{
+ asm volatile("__start:mov $0xdeadbeef, %rax;"
+ "xor %rax, %rax;"
+ "__end:");
+}
+
+int main(int argc, char **argv)
+{
+ extern unsigned char __start;
+ extern unsigned char __end;
+ struct state *state = create_emulator();
+ int rc;
+
+ /* Ensures the emulator is in a valid state. */
+ initialize_emulator(state);
+
+ /* Provide the emulator with instructions to emulate. */
+ state->data = &__start;
+ state->data_available = &__end - &__start;
+
+ /* Execute mov $0xdeadbeef, %rax */
+ rc = step_emulator(state);
+ /* Check that the emulator succeeded. */
+ assert(rc == X86EMUL_CONTINUE);
+ /* Check that 0xdeadbeef was moved to rax. */
+ assert(state->ctxt._regs[REGS_RAX] == 0xdeadbeef);
+
+ /* Execute xor %rax, %rax */
+ rc = step_emulator(state);
+ /* Check that the emulator succeeded. */
+ assert(rc == X86EMUL_CONTINUE);
+ /* Check that xoring rax with itself cleared rax. */
+ assert(state->ctxt._regs[REGS_RAX] == 0);
+
+ /* Free the emulator. */
+ free_emulator(state);
+
+ return 0;