commit 2f6a71fb34c03c4ce04d46b2ec3a91b612d7bc3e
author Bill Richardson <wfrichar@chromium.org> Thu Oct 14 09:25:39 2010 -0700
committer Bill Richardson <wfrichar@chromium.org> Thu Oct 14 09:25:39 2010 -0700
tree 7d0ae09b2b8358d1721bb9a35979d737526adf15
parent 7bfabc008cf3f580a5d1adfd6ef7bb7142a706d0

Handle short read error correctly in vbutil_kernel.c

If you try to read a file that's all zeros, it tries to read a zero-length
kernel blob, fails to do so (or suceeds with an empty result, depending on
your point of view), and prints

  ERROR: Unable to read kernel blob from <file>: Success

That's not very helpful.

This change makes it say

  ERROR: No kernel blob found

instead.

Change-Id: I841ec6e288f47cd9b1f8e9ca1e6da0741ad20e9f

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/3764004

utility/vbutil_kernel.c

diff --git a/utility/vbutil_kernel.c b/utility/vbutil_kernel.c
index 391f5ad..23b6eb2 100644
--- a/utility/vbutil_kernel.c
+++ b/utility/vbutil_kernel.c
@@ -128,6 +128,16 @@
   va_end(ap);
 }
 
+/* Return an explanation when fread() fails. */
+static const char *error_fread(FILE *fp) {
+  const char *retval = "beats me why";
+  if (feof(fp))
+    retval = "EOF";
+  else if (ferror(fp))
+    retval = strerror(errno);
+  clearerr(fp);
+  return retval;
+}
 
 /* Return the smallest integral multiple of [alignment] that is equal
  * to or greater than [val]. Used to determine the number of
@@ -385,7 +395,7 @@
   }
 
   if (0 != stat(filename, &statbuf)) {
-    error("unable to stat %s: %s\n", filename, strerror(errno));
+    error("Unable to stat %s: %s\n", filename, strerror(errno));
     return 0;
   }
 
@@ -409,7 +419,7 @@
   }
 
   if (1 != fread(buf, DEFAULT_PADDING, 1, fp)) {
-    error("Unable to read header from %s: %s\n", filename, strerror(errno));
+    error("Unable to read header from %s: %s\n", filename, error_fread(fp));
     goto unwind_oldblob;
   }
 
@@ -460,6 +470,11 @@
   Debug(" bootloader_size = 0x%" PRIx64 "\n", bp->bootloader_size);
   Debug(" blob_size = 0x%" PRIx64 "\n", bp->blob_size);
 
+  if (!bp->blob_size) {
+    error("No kernel blob found\n");
+    goto unwind_oldblob;
+  }
+
   bp->blob = (uint8_t *)Malloc(bp->blob_size);
   if (!bp->blob) {
     error("Couldn't allocate 0x%" PRIx64 " bytes for blob_t.\n", bp->blob_size);
@@ -468,7 +483,7 @@
 
   /* read it in */
   if (1 != fread(bp->blob, bp->blob_size, 1, fp)) {
-    error("Unable to read kernel blob from %s: %s\n", filename, strerror(errno));
+    error("Unable to read kernel blob from %s: %s\n", filename, error_fread(fp));
     goto unwind_oldblob;
   }