TLD_DEFINE_KEY(9)

🦋 TLD_DEFINE_KEY(9) 🦋

okay bestie, so this one's from the Kernel API Manual and it's literally the glow-up that lets you define a TLD and the global variable key that goes with it, in one little macro. main character energy fr fr 💅

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✨ NAME ✨

TLD_DEFINE_KEY — defines a TLD and a global variable key associated with the TLD. that's the whole vibe 🎀

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🌸 SYNOPSIS 🌸

TLD_DEFINE_KEY (key , name , size );

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💖 ARGUMENTS 💖

• key — the variable name of the key. Cannot exceed TLD_NAME_LEN (respect the limit, queen 👑).
• name — the name of the TLD.
• size — the size of the TLD.

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🧚 DESCRIPTION 🧚

so here's the tea: the macro can only be used in file scope. like, that's not a suggestion, that's the rule 🙈

a global variable key of opaque type, tld_key_t, will be declared and initialized before main starts. (yes, before you even wake up, it's already that girl ✨.) use tld_key_is_err or tld_key_err_or_zero later to check if the key creation succeeded — always do your vibe check, bestie. then pass the key to tld_get_data to get a pointer to the TLD. and bpf programs can also fetch the same key by name, which is lowkey iconic 🦋

also important: the total size of TLDs created using TLD_DEFINE_KEY cannot exceed a page. just enough memory will be allocated for each thread on the first call to tld_get_data — so it's efficient and cute, no cap 💀

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🎀 SEE ALSO 🎀

• Kernel file ./tools/testing/selftests/bpf/prog_tests/task_local_data.h
• tld_create_key(9), tld_get_data(9), tld_free(9) 🌈

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kk that's the whole page, bestie 🫶 — this one's straight from ./tools/testing/selftests/bpf/..., dated October 2026, and yeah, it's still TLD_DEFINE_KEY(9) periodt 💜⭐