Fix Wrong Arithmetic When Computing Guest Code Size #99
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
Previously, we were using program headers to compute total size of ELF memory when loaded in memory. Unfortunately, this is not enough, as some segments that are not loaded may also allocate memory, such as the BSS. This commit fixes this problem by changing this logic to use section headers instead. Signed-off-by: Pedro Henrique Penna <[email protected]>
|
Hello @syntactically, Thank you for the details. Based on them I was able to identify that this undefined behavior was triggered to other changes that I introduced in my private fork. Please, close this PR. |
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Outdated suggestions cannot be applied.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.
Description
This PR closes #98
The
ElfInfo::get_va_size()function is used for determining the size of thegest_codeslot during the construction of the sand memory layout.This function calculates the size based on the loadable program headers, which represent the size of the ELF binary when loaded into memory.
Although the current implementation works, it does not account for guest binaries that have non-loadable segments which still occupy memory at runtime, such as the BSS segment. As a result, the size computation for these binaries will be incorrect.
To fix this, we should consider arithmetic on sections that are tagged as
SHF_ALLOC. From the ELF Specification [1]: