Discussion:
[PATCH v2] multiboot2: clarify usage of the address tag
Roger Pau Monne
2018-06-07 15:59:06 UTC
Permalink
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 <***@citrix.com>
---
Cc: Daniel Kiper <***@oracle.com>
Cc: xen-***@lists.xenproject.org
---
Changes since v1:
- s/elf/@sc{elf}/
- s/Multiboot/Multiboot2/
---
doc/multiboot.texi | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/doc/multiboot.texi b/doc/multiboot.texi
index 2e2d7e74a..3c797787c 100644
--- a/doc/multiboot.texi
+++ b/doc/multiboot.texi
@@ -509,6 +509,12 @@ 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. 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
Daniel Kiper
2018-06-08 09:35:52 UTC
Permalink
Post by Roger Pau Monne
Add a note to spell out that if the address tag is not present the
file should be loaded using the elf header.
---
---
- s/Multiboot/Multiboot2/
---
doc/multiboot.texi | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/doc/multiboot.texi b/doc/multiboot.texi
index 2e2d7e74a..3c797787c 100644
--- a/doc/multiboot.texi
+++ b/doc/multiboot.texi
@@ -509,6 +509,12 @@ assumes that no bss segment is present.
@end table
+Note: This information does not need to be provided if the kernel image
+format or in some other format. Compliant boot loaders must be able to
+tag embedded in the Multiboot2 header.
+
Now it is better. However, there is a lack of information that this tag
should be preferred over the relevant data provided in the ELF header if
both are available in the image. This have to be clear like it is in
Multiboot spec.

Daniel
Roger Pau Monné
2018-06-08 10:08:22 UTC
Permalink
Post by Daniel Kiper
Post by Roger Pau Monne
Add a note to spell out that if the address tag is not present the
file should be loaded using the elf header.
---
---
- s/Multiboot/Multiboot2/
---
doc/multiboot.texi | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/doc/multiboot.texi b/doc/multiboot.texi
index 2e2d7e74a..3c797787c 100644
--- a/doc/multiboot.texi
+++ b/doc/multiboot.texi
@@ -509,6 +509,12 @@ assumes that no bss segment is present.
@end table
+Note: This information does not need to be provided if the kernel image
+format or in some other format. Compliant boot loaders must be able to
+tag embedded in the Multiboot2 header.
+
Now it is better. However, there is a lack of information that this tag
should be preferred over the relevant data provided in the ELF header if
both are available in the image. This have to be clear like it is in
Multiboot spec.
Would you be OK with adding the following sentence at the end:

"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."

Roger.
Daniel Kiper
2018-06-08 10:39:28 UTC
Permalink
Post by Roger Pau Monné
Post by Daniel Kiper
Post by Roger Pau Monne
Add a note to spell out that if the address tag is not present the
file should be loaded using the elf header.
---
---
- s/Multiboot/Multiboot2/
---
doc/multiboot.texi | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/doc/multiboot.texi b/doc/multiboot.texi
index 2e2d7e74a..3c797787c 100644
--- a/doc/multiboot.texi
+++ b/doc/multiboot.texi
@@ -509,6 +509,12 @@ assumes that no bss segment is present.
@end table
+Note: This information does not need to be provided if the kernel image
+format or in some other format. Compliant boot loaders must be able to
+tag embedded in the Multiboot2 header.
+
Now it is better. However, there is a lack of information that this tag
should be preferred over the relevant data provided in the ELF header if
both are available in the image. This have to be clear like it is in
Multiboot spec.
"When the address tag is present it must be used in order to load the
I would put this as a second sentence in note, just after "... some
other format." However, then probably last sentence should be rephrased
a bit.

Daniel
Roger Pau Monné
2018-06-11 09:30:16 UTC
Permalink
Post by Daniel Kiper
Post by Roger Pau Monné
Post by Daniel Kiper
Post by Roger Pau Monne
Add a note to spell out that if the address tag is not present the
file should be loaded using the elf header.
---
---
- s/Multiboot/Multiboot2/
---
doc/multiboot.texi | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/doc/multiboot.texi b/doc/multiboot.texi
index 2e2d7e74a..3c797787c 100644
--- a/doc/multiboot.texi
+++ b/doc/multiboot.texi
@@ -509,6 +509,12 @@ assumes that no bss segment is present.
@end table
+Note: This information does not need to be provided if the kernel image
+format or in some other format. Compliant boot loaders must be able to
+tag embedded in the Multiboot2 header.
+
Now it is better. However, there is a lack of information that this tag
should be preferred over the relevant data provided in the ELF header if
both are available in the image. This have to be clear like it is in
Multiboot spec.
"When the address tag is present it must be used in order to load the
I would put this as a second sentence in note, just after "... some
other format." However, then probably last sentence should be rephrased
a bit.
I think the following is clear enough:

"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."

Roger.
Daniel Kiper
2018-06-11 11:16:42 UTC
Permalink
On Mon, Jun 11, 2018 at 11:30:16AM +0200, Roger Pau Monné wrote:

[...]
Post by Roger Pau Monné
"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
format or contain the address tag embedded in the Multiboot2 header."
LGTM. Thanks!

Daniel

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