Fix check for context propagation support #600
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While the lockdown check for the 'bpf_probe_write_user()' helper was indeed introduced on 5.14[1], it was also backported to the 5.10 tree[2] as well. [1]: torvalds/linux@51e1bb9 [2]: https://elixir.bootlin.com/linux/v5.10.59/A/ident/LOCKDOWN_BPF_WRITE_USER
Codecov ReportAttention:
Additional details and impacted files@@ Coverage Diff @@
## main #600 +/- ##
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+ Coverage 79.68% 80.34% +0.65%
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Files 70 70
Lines 5936 5936
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+ Hits 4730 4769 +39
+ Misses 981 940 -41
- Partials 225 227 +2
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grcevski
approved these changes
Feb 2, 2024
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Hi. I was investigating the issue #390, based on the report that it doesn't work on Debian 11 (Bullseye), which should have a supported kernel:
I managed to start Beyla after recompiling it and was able to trace C programs, like the Apache HTTP Server. The problem is that Go binaries like the testserver weren't working:
After debugging for a while, trying to understand what
uprobe_http2FramerWriteHeaders_returnshad different than other BPF programs, I realized that the VM was running with Secure Boot enabled (which is the default on LXD/Incus). This, in turn, enables the kernel integrity mode:As documented, in cases like that the context propagation might not work. What made it a bit more interesting is the fact that while yes, the lockdown check for the
bpf_probe_write_user()helper was indeed introduced on kernel 5.14, it was also backported to the 5.10 tree as well.Based on these findings, I'm proposing a fix for the context propagation support check.
P.s.: I also checked 5.4 (the previous LTS) and 5.9 versions and didn't find the patch in their trees.