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walkthrough_completeness.md

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Completeness

In Section 6.1 of the paper, we describe that Vinter can find previously-reported crash consistency bugs in NOVA. We identified four relevant patches for NOVA and verified that Vinter detects additional issues before each of these patches. We reproduce this analysis here.

General Approach

For each patch fixing a crash consistency issue, we identify the git commit before and after the crash. The analysis then works as follows:

  • For each commit (before, after):
    • Build the corresponding kernel.
    • Analyze NOVA with Vinter.
    • Summarize results to a file.
  • Finally, compare summarized results to see whether Vinter detected the issue.

Important: The script will check out and compile different NOVA versions. Make sure to return to the initial version once you are finished!

git -C fs-testing/linux/nova checkout vinter-nova
fs-testing/linux/build-kernel.sh nova

PR #89

Analyze with:

# run from Vinter root directory
# arguments: <vm name> <bug id> <commit before patch> <commit after patch>
# run analysis in parallel with -P <number>
fs-testing/scripts/script_reproduce-nova-bug.sh -P 8 vm_nova 89 a1bd8d84faf4 f9d7abcd1e13
# results in results_completeness/89_{before,after}.txt

In the diff, we can see that state extraction failed frequently before the patch. Looking at one of these states (e.g., cat results_completeness/vm_nova/a1bd8d84faf4/test_chmod/semantic_states/state01.txt), we can see that the error message matches the one in the original bug report #88.

PR #92

Analyze with:

fs-testing/scripts/script_reproduce-nova-bug.sh -P 8 vm_nova 92 f9d7abcd1e13 9c85760ab8f7

Similar to the previous issue, we can see that the patch fixed some cases of failing state extraction. Again, the error message (e.g., cat results_completeness/vm_nova/f9d7abcd1e13/test_chmod/semantic_states/state00.txt) matches the one in the original bug report #91.

PR #95

Analyze with:

fs-testing/scripts/script_reproduce-nova-bug.sh -P 8 vm_nova 95 9c85760ab8f7 41d37f1c5a5d

Again, Vinter detects kernel crashes that the patch fixes (e.g., cat results_completeness/vm_nova/9c85760ab8f7/test_rename/semantic_states/state04.txt).

PR #109 for NOVA-Fortis

Analyze with:

fs-testing/scripts/script_reproduce-nova-bug.sh -P 8 vm_nova-protection 109 587e25223ee4 593f927a78a6

Matching the bug report #100, Vinter detects crash images where writing a file after recovery returns ENOSPC errors ("sh: write error: No space left on device"), for example in results_completeness/vm_nova-protection/587e25223ee4/test_hello-world/semantic_states/state02.txt.

Note that the shell error message might not print to the terminal (e.g., with cat) because it ends with a carriage return (^M).

Cleanup

Remember to return to the initial NOVA version, as detailed above!