Revert "Add libfuzzer target to fuzz/x86_instruction_emulator"

This reverts commit af67ae49ce for
breaking the build with at least older gcc.

tools/fuzz/x86_instruction_emulator/Makefile

@@ -3,7 +3,7 @@ include $(XEN_ROOT)/tools/Rules.mk
 
 .PHONY: x86-insn-fuzz-all
 ifeq ($(CONFIG_X86_64),y)
-x86-insn-fuzz-all: x86-insn-fuzzer.a fuzz-emul.o afl libfuzzer
+x86-insn-fuzz-all: x86-insn-fuzzer.a fuzz-emul.o afl
 else
 x86-insn-fuzz-all:
 endif
@@ -58,9 +58,6 @@ afl-harness: afl-harness.o $(OBJS) cpuid.o wrappers.o
 afl-harness-cov: afl-harness-cov.o $(patsubst %.o,%-cov.o,$(OBJS)) cpuid.o wrappers.o
 	$(CC) $(CFLAGS) $(GCOV_FLAGS) $(addprefix -Wl$(comma)--wrap=,$(WRAPPED)) $^ -o $@
 
-libfuzzer-harness: $(OBJS) cpuid.o wrappers.o
-	$(CC) $(CFLAGS) $(LIB_FUZZING_ENGINE) -fsanitize=fuzzer $(addprefix -Wl$(comma)--wrap=,$(WRAPPED)) $^ -o $@
-
 # Common targets
 .PHONY: all
 all: x86-insn-fuzz-all
@@ -70,8 +67,7 @@ distclean: clean
 
 .PHONY: clean
 clean:
-	rm -f *.a *.o $(DEPS_RM) *.gcda *.gcno *.gcov
-	rm -f afl-harness afl-harness-cov libfuzzer-harness
+	rm -f *.a *.o $(DEPS_RM) afl-harness afl-harness-cov *.gcda *.gcno *.gcov
 	rm -rf x86_emulate x86-emulate.c x86-emulate.h wrappers.c cpuid.c
 
 .PHONY: install
@@ -85,7 +81,4 @@ afl: afl-harness
 .PHONY: afl-cov
 afl-cov: afl-harness-cov
 
-.PHONY: libfuzzer
-libfuzzer: libfuzzer-harness
-
 -include $(DEPS_INCLUDE)

tools/fuzz/x86_instruction_emulator/fuzz-emul.c

@@ -906,12 +906,14 @@ int LLVMFuzzerTestOneInput(const uint8_t *data_p, size_t size)
 
     if ( size <= DATA_OFFSET )
     {
-        return -1;
+        printf("Input too small\n");
+        return 1;
     }
 
     if ( size > FUZZ_CORPUS_SIZE )
     {
-        return -1;
+        printf("Input too large\n");
+        return 1;
     }
 
     memcpy(&input, data_p, size);

tools/tests/x86_emulator/wrappers.c

@@ -91,17 +91,6 @@ int __wrap_snprintf(char *buf, size_t n, const char *fmt, ...)
     return rc;
 }
 
-int __wrap_vsnprintf(char *buf, size_t n, const char *fmt, va_list varg)
-{
-    int rc;
-
-    emul_save_fpu_state();
-    rc = __real_vsnprintf(buf, n, fmt, varg);
-    emul_restore_fpu_state();
-
-    return rc;
-}
-
 char *__wrap_strstr(const char *s1, const char *s2)
 {
     char *s;