linux-kernel - [PATCH 3/3] Demonstrating unit testing via simple-harness

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Date:   Tue, 21 May 2019 17:39:24 +0200
From:   Sam Caccavale <samcacc@...zon.de>
To:     unlisted-recipients:; (no To-header on input)
CC:     <samcacc@...zon.de>, <samcaccavale@...il.com>,
        <nmanthey@...zon.de>, <wipawel@...zon.de>, <dwmw@...zon.co.uk>,
        <mpohlack@...zon.de>, <graf@...zon.de>, <karahmed@...zon.de>,
        <andrew.cooper3@...rix.com>, <JBeulich@...e.com>,
        <pbonzini@...hat.com>, <rkrcmar@...hat.com>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <bp@...en8.de>, <hpa@...or.com>,
        <paullangton4@...il.com>, <anirudhkaushik@...gle.com>,
        <x86@...nel.org>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH 3/3] Demonstrating unit testing via simple-harness

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.

---
 tools/fuzz/x86_instruction_emulation/Makefile |  7 ++-
 .../simple-harness.c                          | 49 +++++++++++++++++++
 2 files changed, 54 insertions(+), 2 deletions(-)
 create mode 100644 tools/fuzz/x86_instruction_emulation/simple-harness.c

diff --git a/tools/fuzz/x86_instruction_emulation/Makefile b/tools/fuzz/x86_instruction_emulation/Makefile
index d2854a332605..bb29149ae0f7 100644
--- a/tools/fuzz/x86_instruction_emulation/Makefile
+++ b/tools/fuzz/x86_instruction_emulation/Makefile
@@ -43,7 +43,10 @@ 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: fuzz_deps
 fuzz_deps:
@@ -54,4 +57,4 @@ fuzz_deps:
 
 .PHONY: clean
 clean:
-	$(RM) -r *.o afl-harness
+	$(RM) -r *.o afl-harness simple-harness
diff --git a/tools/fuzz/x86_instruction_emulation/simple-harness.c b/tools/fuzz/x86_instruction_emulation/simple-harness.c
new file mode 100644
index 000000000000..9601aafb9423
--- /dev/null
+++ b/tools/fuzz/x86_instruction_emulation/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;
+}
-- 
2.17.1




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