Add LFI_PREFIX_PAD for postlinker

Author: zyedidia

lfi-postlink/amd64.c

@@ -448,7 +448,7 @@ amd64_postlink(uint8_t* buf, size_t sz)
             nopfix(code, p->filesz, args.bundle, p->vaddr);
             while (count + args.bundle <= p->filesz) {
                 /* bundlefix(&code[count], p->filesz - count, args.bundle, p->vaddr + count); */
-                if (!args.noprefix && false)
+                if (args.prefix)
                     padrewrite(&code[count], args.bundle, p->vaddr + count);
                 callrewrite(&code[count], args.bundle, p->vaddr + count);
                 count += args.bundle;

lfi-postlink/main.c

@@ -17,7 +17,7 @@ static char args_doc[] = "INPUT";
 enum {
     ARG_bundle    = 0x80,
     ARG_meter     = 0x81,
-    ARG_noprefix  = 0x82,
+    ARG_prefix    = 0x82,
     ARG_precise   = 0x83,
 };
 
@@ -27,7 +27,7 @@ static struct argp_option options[] = {
     { "bundle",         ARG_bundle,        "SIZE", 0, "set the bundle size" },
     { "meter",          ARG_meter,         "TYPE", 0, "set the metering type (branch,fp,timer)" },
     { "precise",        ARG_precise,       0,      0, "enable precise metering" },
-    { "no-prefix-pad",  ARG_noprefix,      0,      0, "disable prefix padding" },
+    { "prefix-pad",     ARG_prefix,      0,      0, "enable prefix padding" },
     { 0 },
 };
 
@@ -63,8 +63,8 @@ parse_opt(int key, char* arg, struct argp_state* state)
     case ARG_precise:
         args->precise = true;
         break;
-    case ARG_noprefix:
-        args->noprefix = true;
+    case ARG_prefix:
+        args->prefix = true;
         break;
     case ARGP_KEY_ARG:
         args->input = arg;
@@ -104,6 +104,10 @@ main(int argc, char** argv)
     args.input = "";
     argp_parse(&argp, argc, argv, ARGP_NO_HELP, 0, &args);
 
+    const char* prefix = getenv("LFI_PREFIX_PAD");
+    if (prefix && strcmp(prefix, "1") == 0)
+        args.prefix = true;
+
     if (strcmp(args.input, "") == 0) {
         fprintf(stderr, "error: no input file\n");
         return 1;

lfi-postlink/postlink.h

@@ -16,7 +16,7 @@ struct arguments {
     char* arch;
     int bundle;
     enum meter meter;
-    bool noprefix;
+    bool prefix;
     bool precise;
 };