[KernelCache] Set segment flags based on how XNU initially maps them #7519
Conversation
This file contains hidden or 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
… them XNU maps kernel cache segments in with different permissions than the load commands indicate. For instance, `__DATA_CONST` is initially mapped as read-write before later being re-mapped as read-only. Treating it as read-only results in analysis falsely assuming that global variables cannot change. To work around this we maintain a mapping from segment name to initial permissions (i.e., most lax permissions) and favor them over permissions derived from the segment load command. Section semantics are also derived from the segment's permissions when the segment is present in the mapping. The mapping is based on the initial permissions established by `arm_vm_prot_init` within the XNU source.
bdash
force-pushed
the
test_kc_segment_perms
branch
from
cb6e021 to
9a8faad
Compare
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Outdated suggestions cannot be applied.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.
XNU maps kernel cache segments in with different permissions than the load commands indicate. For instance,
__DATA_CONSTis initially mapped as read-write before later being re-mapped as read-only. Treating it as read-only results in analysis falsely assuming that global variables cannot change.To work around this we maintain a mapping from segment name to initial permissions (i.e., most lax permissions) and favor them over permissions derived from the segment load command. Section semantics are also derived from the segment's permissions when the segment is present in the mapping.
The mapping is based on the initial permissions established by
arm_vm_prot_initwithin the XNU source.Related to #6718.