5546c06a12
Starting with Linux 7.0, the rseq feature size has grown to 33 bytes
and AT_RSEQ_ALIGN has increased to 64. This causes sizeof(struct rseq)
from the uapi header to be 64 (33 bytes padded to aligned(32)), while
the actual registration size used by glibc (__rseq_size) is 33.
The rseq01 test was using sizeof(struct rseq) as the registration
size and a test-local __rseq_abi variable (with only 32-byte
alignment from the uapi header) as the rseq area. Both are
wrong on kernel 7.0:
- The kernel now checks alignment against __alignof__(struct rseq)
which is 64 internally; the 32-byte-aligned test variable may
not satisfy this.
- sizeof(struct rseq) = 64 does not match the feature size of 33
that glibc registered with, so re-registration with a different
size fails.
Fix by:
- Using __rseq_size (the feature size reported by glibc) as the
registration size instead of sizeof(struct rseq).
- Using the glibc-provided rseq area (at thread_pointer() +
__rseq_offset) which is allocated with proper AT_RSEQ_ALIGN
alignment, instead of a test-local variable.
Both fall back to the previous behavior when glibc rseq support
is not available.
This mirrors the glibc fix:
https://sourceware.org/cgit/glibc/commit/?id=67f303b47dc584f204e3f2441b9832082415eebc
Assisted-by: Claude Code (claude-opus-4-6):claude-opus-4-6@default
Signed-off-by: Adrian Reber <areber@redhat.com>
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|---|---|---|
| .circleci | ||
| .github | ||
| compel | ||
| contrib | ||
| coredump | ||
| crit | ||
| criu | ||
| Documentation | ||
| images | ||
| include | ||
| lib | ||
| plugins | ||
| scripts | ||
| soccr | ||
| test | ||
| .cirrus.yml | ||
| .clang-format | ||
| .codespellrc | ||
| .gitignore | ||
| .lgtm.yml | ||
| .mailmap | ||
| CLAUDE.md | ||
| CONTRIBUTING.md | ||
| COPYING | ||
| CREDITS | ||
| flake.lock | ||
| flake.nix | ||
| GEMINI.md | ||
| INSTALL.md | ||
| MAINTAINERS | ||
| MAINTAINERS_GUIDE.md | ||
| Makefile | ||
| Makefile.compel | ||
| Makefile.config | ||
| Makefile.install | ||
| Makefile.versions | ||
| README.md | ||
CRIU -- A project to implement checkpoint/restore functionality for Linux
CRIU (stands for Checkpoint and Restore in Userspace) is a utility to checkpoint/restore Linux tasks.
Using this tool, you can freeze a running application (or part of it) and checkpoint it to a hard drive as a collection of files. You can then use the files to restore and run the application from the point it was frozen at. The distinctive feature of the CRIU project is that it is mainly implemented in user space. There are some more projects doing C/R for Linux, and so far CRIU appears to be the most feature-rich and up-to-date with the kernel.
CRIU project is (almost) the never-ending story, because we have to always keep up with the Linux kernel supporting checkpoint and restore for all the features it provides. Thus we're looking for contributors of all kinds -- feedback, bug reports, testing, coding, writing, etc. Please refer to CONTRIBUTING.md if you would like to get involved.
The project started as the way to do live migration for OpenVZ Linux containers, but later grew to more sophisticated and flexible tool. It is currently used by (integrated into) OpenVZ, LXC/LXD, Docker, and other software, project gets tremendous help from the community, and its packages are included into many Linux distributions.
The project home is at http://criu.org. This wiki contains all the knowledge base for CRIU we have. Pages worth starting with are:
- Installation instructions
- A simple example of usage
- Examples of more advanced usage
- Troubleshooting can be hard, some help can be found here, here and here
Checkpoint and restore of simple loop process
Advanced features
As main usage for CRIU is live migration, there's a library for it called P.Haul. Also the project exposes two cool core features as standalone libraries. These are libcompel for parasite code injection and libsoccr for TCP connections checkpoint-restore.
Live migration
True live migration using CRIU is possible, but doing all the steps by hands might be complicated. The phaul sub-project provides a Go library that encapsulates most of the complexity. This library and the Go bindings for CRIU are stored in the go-criu repository.
Parasite code injection
In order to get state of the running process CRIU needs to make this process execute some code, that would fetch the required information. To make this happen without killing the application itself, CRIU uses the parasite code injection technique, which is also available as a standalone library called libcompel.
TCP sockets checkpoint-restore
One of the CRIU features is the ability to save and restore state of a TCP socket without breaking the connection. This functionality is considered to be useful by itself, and we have it available as the libsoccr library.
Licence
The project is licensed under GPLv2 (though files sitting in the lib/ directory are LGPLv2.1).
All files in the images/ directory are licensed under the Expat license (so-called MIT). See the images/LICENSE file.