fuzz/x86_emulate: Move definitions into a header

Move fuzz-emul.c function prototypes into a header.  Also share the
definition of the input size (rather than hard-coding it in
fuzz-emul.c).

Signed-off-by: George Dunlap <george.dunlap@citrix.com>

tools/fuzz/x86_instruction_emulator/afl-harness.c

@@ -4,12 +4,8 @@
 #include <stdlib.h>
 #include <string.h>
 #include <getopt.h>
+#include "fuzz-emul.h"
 
-extern int LLVMFuzzerInitialize(int *argc, char ***argv);
-extern int LLVMFuzzerTestOneInput(const uint8_t *data_p, size_t size);
-extern unsigned int fuzz_minimal_input_size(void);
-
-#define INPUT_SIZE  4096
 static uint8_t input[INPUT_SIZE];
 
 int main(int argc, char **argv)

tools/fuzz/x86_instruction_emulator/fuzz-emul.c

@@ -16,6 +16,7 @@
 #include <xen/xen.h>
 
 #include "x86-emulate.h"
+#include "fuzz-emul.h"
 
 #define MSR_INDEX_MAX 16
 
@@ -29,7 +30,7 @@ struct fuzz_corpus
     struct cpu_user_regs regs;
     struct segment_register segments[SEG_NUM];
     unsigned long options;
-    unsigned char data[4096];
+    unsigned char data[INPUT_SIZE];
 } input;
 #define DATA_OFFSET offsetof(struct fuzz_corpus, data)
 
@@ -827,7 +828,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data_p, size_t size)
         return 1;
     }
 
-    if ( size > sizeof(input) )
+    if ( size > INPUT_SIZE )
     {
         printf("Input too large\n");
         return 1;
@@ -858,6 +859,8 @@ int LLVMFuzzerTestOneInput(const uint8_t *data_p, size_t size)
 
 unsigned int fuzz_minimal_input_size(void)
 {
+    BUILD_BUG_ON(DATA_OFFSET > INPUT_SIZE);
+
     return DATA_OFFSET + 1;
 }
 

tools/fuzz/x86_instruction_emulator/fuzz-emul.h

@@ -0,0 +1,10 @@
+#ifndef FUZZ_EMUL_H
+# define FUZZ_EMUL_H
+
+extern int LLVMFuzzerInitialize(int *argc, char ***argv);
+extern int LLVMFuzzerTestOneInput(const uint8_t *data_p, size_t size);
+extern unsigned int fuzz_minimal_input_size(void);
+
+#define INPUT_SIZE  4096
+
+#endif /* ifdef FUZZ_EMUL_H */