feat: legacy XADD and correct JIT code buffer sizing#145
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Hi, @qmonnet! Could you please take a look at this PR when you have a moment? Thanks! |
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Yep sorry, it's been a busy few weeks, but this is still on my list. I'll try to take a deeper look at it soon. |
qmonnet
requested changes
May 29, 2026
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Thanks, and apologies again for the delay.
It looks good overall, but I've got two comments:
- Can you please adjust the verifier check to keep rejecting newer atomic operations (see comment below)?
- Could you please make the JIT allocation fix a separate commit? It would make it easier to look at it again in the future, if necessary.
There's also test_jit_xadd_w_dw() which currently doesn't pass with --no-default-features ("Error: No custom executable memory set, call set_jit_exec_memory() to set one").
Add non-fetch ST_W_XADD/ST_DW_XADD so eBPF programs that use atomic add-to-memory can run in the interpreter, x86_64 JIT, and Cranelift; extend the verifier and tests accordingly. Signed-off-by: Sergey Kacheev <s.kacheev@gmail.com>
Fix JIT allocation by sizing the executable buffer with a dry run before emitting code, instead of assuming a single fixed page. Signed-off-by: Sergey Kacheev <s.kacheev@gmail.com>
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Thanks for the hints and explanations! |
qmonnet
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Jun 3, 2026
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Looks good now, much better with two commits. Thank you!
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Hi, and thanks for a great project.
I hit a wall: my program uses atomic operations and wouldn’t run- it was hitting unimplemented. After digging through the code, adding support for the legacy XADD instructions looked straightforward, so I went ahead and implemented it.
I might come back later with full atomic support, but for now I’d like to get this merged.
Thanks!