Update seccompiler to use libseccomp #4926
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Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #4926 +/- ##
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- Coverage 83.95% 83.07% -0.89%
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Files 248 244 -4
Lines 27839 26634 -1205
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- Hits 23371 22125 -1246
- Misses 4468 4509 +41
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roypat
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I'm curious, what does this mean? and how was this evaluated? |
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(just resolved merge conflict so there's a chance my approval will survive me going on vacation) |
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roypat
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Jan 15, 2025
pb8o
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roypat
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pb8o
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libseccomp provides a better quality compiler for BPF seccomp programs than our current implementation. In our testing it produces BPF code with ~65% less instructions which makes final binaries smaller which in turn makes Firecracker binary smaller because we include them into Firecracker at build time. For this transition we create a minimal set of bindings for `libseccomp` in order to simplify maintenance and avoid adding additional dependencies. The only tricky issue with this transition is the way `ioctl` and other syscalls are checked with libseccomp. It always adds a check for the high bits of the request to be 0. Unfortunately when we build with `musl`, some syscalls like `ioctl` have upper bits set to 1. Because of this, we replace `Eq` with `MaskedEq` with mask `0x00000000FFFFFFFF` when the argument is 32bits. This commit also removes dependency of firecracker and vmm crates on the seccompiler crate. Co-authored-by: Pablo Barbáchano <[email protected]> Signed-off-by: Egor Lazarchuk <[email protected]>
Since we depend on libseccomp in the previous commit, these commands to update the syscall table are no longer needed. Signed-off-by: Pablo Barbáchano <[email protected]>
According to https://www.man7.org/linux/man-pages/man2/PR_SET_SECCOMP.2const.html using `prctl` for setting seccomp filer is deprecated, so switch to using `syscall` instead. Signed-off-by: Egor Lazarchuk <[email protected]>
Replace __errno_location() with std::io::Error::last_os_error() as a more standard of getting errno value. Signed-off-by: Egor Lazarchuk <[email protected]>
The error enum had only 1 element and we can replace it with alias for simplicity. Signed-off-by: Egor Lazarchuk <[email protected]>
Add a note about updating backend for seccompiler to libseccomp. Signed-off-by: Egor Lazarchuk <[email protected]>
Kani on x86 for some reason cannot find libseccomp by default, so we add additional path to the build.rs Signed-off-by: Egor Lazarchuk <[email protected]>
Add a note about libseccomp usage in Firecracker build process and in the seccomp-bin. Signed-off-by: Egor Lazarchuk <[email protected]>
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Changes
Replace our custom implementation of a seccompiler with libseccomp.
By out test,
libseccompproduces ~65% smaller binaries which is very beneficial as we embed the combination of those into the Firecracker.In order to interact with
libseccompwe add custom bindings which contain only the needed set of methods, constants needed for our use case. This simplifies the maintenance and avoids adding dependencies.Reason
libseccompprovides better quality compiler for BPF seccomp programs than our current implementation.License Acceptance
By submitting this pull request, I confirm that my contribution is made under
the terms of the Apache 2.0 license. For more information on following Developer
Certificate of Origin and signing off your commits, please check
CONTRIBUTING.md.PR Checklist
tools/devtool checkstyleto verify that the PR passes theautomated style checks.
how they are solving the problem in a clear and encompassing way.
in the PR.
CHANGELOG.md.Runbook for Firecracker API changes.
integration tests.
TODO.rust-vmm.