[PATCH v4] xen: arm: Update arm64 image header

[Dirk Behme <dirk.behme@de.bosch.com>]

With the Linux kernel commits

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/Documentation/arm64/booting.txt?id=4370eec05a887b0cd4392cd5dc5b2713174745c0

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/Documentation/arm64/booting.txt?id=a2c1d73b94ed49f5fac12e95052d7b140783f800

the arm64 image header changed. While the size of the header isn't changed,
some members have changed their usage.

Update Xen to this updated image header.

The main changes are that the first magic is gone and that there is an
image size, now.

In case we read a size != 0, let's use this image size, now. This does
allow us to check if the kernel Image is larger than the size given in
the device tree, too.

Additionally, add an error message if the magic is not found. This might
be the case with kernel's < 3.12 prior to

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4370eec05a887b0cd4392cd5dc5b2713174745c0

which introduced the second magic.

This is acceptable as the support of Xen for ARM64 in Linux has been added
in Linux 3.11 and the number of boards supported by Linux 3.11 on ARM64 is
very limited: ARM models and X-gene. And for the latter it was an early
support with only the serial and timer upstreamed.

Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
---

Changes in v4: Print header error only based on ZIMAGE64_MAGIC_V0. Drop comment
               and unnecessary if statement.

Changes in v3: Just update of the commit message regarding the support
               for kernels < 3.12. No change to the patch itself.

 xen/arch/arm/kernel.c | 43 +++++++++++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 16 deletions(-)

diff --git a/xen/arch/arm/kernel.c b/xen/arch/arm/kernel.c
index 9871bd9..1797097 100644
--- a/xen/arch/arm/kernel.c
+++ b/xen/arch/arm/kernel.c
@@ -29,7 +29,7 @@
 #define ZIMAGE32_MAGIC 0x016f2818
 
 #define ZIMAGE64_MAGIC_V0 0x14000008
-#define ZIMAGE64_MAGIC_V1 0x644d5241 /* "ARM\x64" */
+#define ZIMAGE64_MAGIC 0x644d5241 /* "ARM\x64" */
 
 struct minimal_dtb_header {
     uint32_t magic;
@@ -335,17 +335,19 @@ static int kernel_zimage64_probe(struct kernel_info *info,
 {
     /* linux/Documentation/arm64/booting.txt */
     struct {
-        uint32_t magic0;
-        uint32_t res0;
-        uint64_t text_offset;  /* Image load offset */
-        uint64_t res1;
+        union {
+                uint32_t code0;
+                uint32_t magic0; /* Old header magic */
+        };
+        uint32_t code1;
+        uint64_t text_offset;  /* Image load offset, little endian */
+        uint64_t image_size;   /* Effective Image size, little endian */
+        uint64_t flags;
         uint64_t res2;
-        /* zImage V1 only from here */
         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 +356,29 @@ 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 ) {
+        if ( zimage.magic0 == ZIMAGE64_MAGIC_V0 )
+             printk(XENLOG_ERR "No valid magic found in header! Kernel too old\n");
         return -EINVAL;
+    }
 
-    /* Currently there is no length in the header, so just use the size */
     start = 0;
-    end = size;
 
     /*
-     * Given the above this check is a bit pointless, but leave it
-     * here in case someone adds a length field in the future.
+     * Where image_size is non-zero image_size is little-endian
+     * and must be respected.
      */
-    if ( (end - start) > size )
+    if ( zimage.image_size )
+        end = zimage.image_size;
+    else
+        end = size;
+
+    if ( (end - start) > size ) {
+        printk(XENLOG_ERR "Error: Kernel Image size: %lu bytes > bootmodule size: %lu bytes\n",
+               zimage.image_size, (uint64_t)size);
+        printk(XENLOG_ERR "The field 'size' does not match the size of blob!\n");
         return -EINVAL;
+    }
 
     info->zimage.kernel_addr = addr;
     info->zimage.len = end - start;
-- 
2.8.0


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