[PATCH v3] multiboot2: clarify usage of the address tag

[Roger Pau Monne <roger.pau@citrix.com>]

Add a note to spell out that if the address tag is not present the
file should be loaded using the elf header.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Cc: Daniel Kiper <daniel.kiper@oracle.com>
Cc: xen-devel@lists.xenproject.org
---
Changes since v2:
 - Clarify that the address tag must be used if present.

Changes since v1:
 - s/elf/@sc{elf}/
 - s/Multiboot/Multiboot2/
---
 doc/multiboot.texi | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/doc/multiboot.texi b/doc/multiboot.texi
index 2e2d7e74a..df8a0d056 100644
--- a/doc/multiboot.texi
+++ b/doc/multiboot.texi
@@ -509,6 +509,14 @@ assumes that no bss segment is present.
 
 @end table
 
+Note: This information does not need to be provided if the kernel image
+is in @sc{elf} format, but it must be provided if the image is in a.out
+format or in some other format. When the address tag is present it must
+be used in order to load the image, regardless of whether an @sc{elf}
+header is also present. Compliant boot loaders must be able to load
+images that are either in @sc{elf} format or contain the address tag
+embedded in the Multiboot2 header.
+
 @subsection The entry address tag of Multiboot2 header
 
 @example
-- 
2.17.1