GELF_GETAUXV(3)

💖 GELF_GETAUXV 💖

okay so bestie, welcome to gelf_getauxv — a page from the Libelf Programmer's Manual (yes, that libelf, the one that lives in elfutils land) 💅

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✨ NAME ✨

gelf_getauxv — grab class-independent info out of an auxiliary vector at whatever index you want, no cap 🎀

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🌸 SYNOPSIS 🌸

#include <gelf.h>

GElf_auxv_t *gelf_getauxv (Elf_Data *data, int ndx, GElf_auxv_t *dst);

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🦋 DESCRIPTION 🦋

So the whole vibe is: you pull one auxiliary vector entry out of data, at index ndx, and you tuck it into the class-independent representation that dst is pointing at. That's it. That's the function. ✨

Now here's the part you cannot skip, iykyk: data must be an Elf_Data* that's associated with an ELF note of type NT_AUXV, and its d_type must be set to ELF_T_AUXV. Not optional. Not negotiable. 👑

If you need to get an Elf_Data* that actually has a d_type of ELF_T_AUXV, that's what elf_getdata_rawchunk(3) is for — go say hi to it. And where do you find NT_AUXV notes chilling? Normally in core files 💀. You can also just read the auxiliary vector straight out of /proc/PID/auxv if that's more your thing.

And if you want the whole lore on what an auxiliary vector even is, go read getauxval(3). It's giving lore drop. 📚

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💜 PARAMETERS 💜

• data — pointer to an Elf_Data of a note with type NT_AUXV, and it must have its d_type set to ELF_T_AUXV. Peep elf_getdata_rawchunk(3) for more deets.
• ndx — the index of the auxiliary vector entry you want, inside data.
• dst — pointer to a caller-provided GElf_auxv_t struct where the requested entry gets stored. Must not be NULL. Like, don't. 🚫

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🌈 RETURN VALUE 🌈

On success, this function updates dst with the auxiliary vector entry you asked for and hands dst right back to you. Slay. 🫶

On failure, it returns NULL and sets elf_errno. Classic.

Special little edge case bestie: if data is NULL, then NULL is returned and elf_errno is not set. So don't go blaming elf_errno for that one, it did nothing wrong. 🙈

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👑 SEE ALSO 👑

elf_getdata_rawchunk(3), getauxval(3) libelf(3), elf(5)

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💅 ATTRIBUTES 💅

The interface, the attribute, the value — but make it a list because tables are not the vibe here:

• Interface: gelf_getauxv()
• Attribute: Thread safety
• Value: MT-Safe

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😭 REPORTING BUGS 😭

Found a bug? Report it to <elfutils-devel@sourceware.org> or hit up https://sourceware.org/bugzilla/. They wanna know, fr fr. 🐛

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🧚 HISTORY 🧚

gelf_getauxv first appeared in elfutils 0.130. Heads up though — this function is an elfutils libelf extension, which means it may not be available in other libelf implementations. So if you're porting somewhere else, do a vibe check first. ⭐

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and that's the whole page bestie, you ate it, periodt 💖

this has been Libelf, dated 2025-12-31 — go forth and read your auxiliary vectors, main character 🌸✨