[PATCH v3] linux-gen: fix unaligned access in checksum calculation #1946
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
odpbuild
changed the title
JereLeppanen
approved these changes
Nov 9, 2023
JannePeltonen
force-pushed
the
fix-unaligned
branch
from
d216dcb
to
49b2c62
Compare
odpbuild
changed the title
|
v2: there was still a possible unaligned uint16_t pointer that is now fixed. Also fixed the casts to use the unaligned types. |
Architectures that support unaligned access do not necessarily support it for all instructions that a compiler might choose to use. Therefore we should not mispresent the alignment of an object to the compiler even when unaligned access is typically supported. The current checksum code casts a potentially unaligned address to a pointer to uint32_t when _ODP_UNALIGNED is set. This typically works but may, in some cases, result in generation of invalid code. In particular, when targeting AArch32 (which supports unaligned access for regular loads and stores) gcc-12.2 generated LDM instructions which always reguire 4-byte alignment. Fix the problem by informing the compiler about the non-standard alignment by using a type attribute. Signed-off-by: Janne Peltonen <janne.peltonen@nokia.com> Reviewed-by: Jere Leppänen <jere.leppanen@nokia.com>
JannePeltonen
force-pushed
the
fix-unaligned
branch
from
49b2c62
to
aeff68a
Compare
odpbuild
changed the title
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Architectures that support unaligned access do not necessarily support it for all instructions that a compiler might choose to use. Therefore we should not mispresent the alignment of an object to the compiler even when unaligned access is typically supported.
The current checksum code casts a potentially unaligned pointer to uint32_t when _ODP_UNALIGNED is set. This typically works but may, in some cases, result in generation of invalid code. In particular, when targeting AArch32 (which supports unaligned access for regular loads and stores) gcc-12.2 generated LDM instructions which always reguire 4-byte alignment.
Fix the problem by informing the compiler about the non-standard alignment by using a type attribute.