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Re: [Xen-devel] [PATCH v3] xen: arm: Update arm64 image header





On 26/06/2016 10:30, Dirk Behme wrote:
Hi Julien,

Hi Dirk,

On 26.06.2016 10:29, Julien Grall wrote:
Hello Dirk,

On 26/06/2016 06:47, Dirk Behme wrote:
On 23.06.2016 17:18, Julien Grall wrote:
On 23/06/16 07:38, Dirk Behme wrote:
+        uint64_t res2;
          uint64_t res3;
          uint64_t res4;
-        uint64_t res5;
-        uint32_t magic1;
-        uint32_t res6;
+        uint32_t magic;        /* Magic number, little endian,
"ARM\x64" */
+        uint32_t res5;
      } zimage;
      uint64_t start, end;

@@ -354,20 +353,30 @@ static int kernel_zimage64_probe(struct
kernel_info *info,

      copy_from_paddr(&zimage, addr, sizeof(zimage));

-    if ( zimage.magic0 != ZIMAGE64_MAGIC_V0 &&
-         zimage.magic1 != ZIMAGE64_MAGIC_V1 )
+    if ( zimage.magic != ZIMAGE64_MAGIC ) {
+        printk(XENLOG_ERR "No valid magic found in header! Kernel
too old?\n");

I have found why there were no error messages here before. The
function kernel_probe will try the different formats supported one by
one.

So this message will be printed if the kernel is an ARM32 image, which
will confuse the user. So I would print this message only when
zimage.magic0 is equal to ZIMAGE64_MAGIC_V0.


Which we don't have with the recent header format any more.

Well, we control the structure in Xen. So we could re-introduce the
field magic0 through an union.

 > This does
mean I drop this message again, as it doesn't make sense if the
magic is
used for the format detection.

I would still prefer to keep an error message when only MAGIC_V0 is
present. This will avoid people to spend time understanding why it
does not work anymore.


This way

if ( zimage.magic != ZIMAGE64_MAGIC ) {
      if ( zimage.magic0 == ZIMAGE64_MAGIC_V0 )
            printk(XENLOG_ERR "No valid magic found in header! Kernel
too old?\n");
      return -EINVAL;
}

with magic0 being a union with code0?

Yes, although I would drop the question marks at the end of the second sentence. We know that the kernel is too old.

Thank you for doing this.

Regards,

--
Julien Grall

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