Refactor http2_grpc to leverage tail calls #1447
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rafaelroquetto
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rafaelroquetto
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Dec 12, 2024
| @@ -0,0 +1,22 @@ | |||
| #ifndef K_TRACER_TAILCALL_H | |||
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This file was necessary to avoid a cyclic header dependency.
Codecov ReportAll modified and coverable lines are covered by tests ✅
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## main #1447 +/- ##
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- Coverage 76.86% 65.36% -11.50%
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Files 149 148 -1
Lines 15252 15255 +3
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- Hits 11723 9972 -1751
- Misses 2911 4541 +1630
- Partials 618 742 +124
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rafaelroquetto
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Dec 12, 2024
| http2_grpc_request_t prev_info; | ||
| u8 has_prev_info; | ||
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| int pos; //FIXME should be size_t equivalent |
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This FIXME will be addressed separately - there are too many other places to check and tweak.
mariomac
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Dec 12, 2024
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The latest kernel versions have changed the way the verifier deals with scalar spills, reducing its tolerance towards complex programs - for a comprehensive discussion, please refer to
https://lore.kernel.org/bpf/[email protected]/T/
Our http2 code therefore no longer passes the verifier, owing to mostly a complex for loop. This PR splits the code into different bpf programs that are now tail called, and changes the
_for_loop to be a hybrid of a recursive bpf_tail_call and a loop with less iterations. This approach was chosen because neither do we want to bpf_tail_call/recurse for each iteration, nor do we wish to usebpf_loopas constrains our program to kernel versions greater than 5.17.