GELF_UPDATE_AUXV(3)

✨ GELF_UPDATE_AUXV ✨

ok so this is from the Libelf Programmer's Manual bestie, section 3, and it's literally about poking new values into the auxiliary vector 💅

---

🌸 NAME 🌸

gelf_update_auxv — update the info in the auxiliary vector at the index you picked 👑

---

🦋 SYNOPSIS 🦋

#include <gelf.h>

int gelf_update_auxv (Elf_Data *data, int ndx, GElf_auxv_t *src);

---

💖 DESCRIPTION 💖

So basically: you take a class-independent auxiliary vector entry from src and you copy it into the NT_AUXV note that's associated with data, at index ndx. That's the whole vibe. 🎀

If you want the full lore on what the auxiliary vector even is, go peek at getauxval(3) — she explains it way better than I could in one breath.

---

🌈 PARAMETERS 🌈

• data — a pointer to an Elf_Data that's associated with an NT_AUXV ELF note. data->d_type should be ELF_T_AUXV. These NT_AUXV notes are normally found hanging out in core files. You can also read the auxiliary vector straight from /proc/PID/auxv of a live process — but heads up, in that case this function does not write back to data itself. no cap. 🙈
• ndx — the zero-based index of the auxiliary vector entry you want to update inside data. zero-based, bestie, we start counting at 0 around here.
• src — a pointer to an auxiliary vector entry that you provide. For ELFCLASS32 binaries, a_type and a_val have to fit inside unsigned 32-bit values. and src must not be NULL. 💀

---

⭐ RETURN VALUE ⭐

When it works: you get a non-zero value back, the auxiliary vector entry at index ndx in data gets updated, and the section or segment associated with data gets marked with ELF_F_DIRTY (she's dirty, she knows 🫶).

When it doesn't work: you get zero, and elf_errno is set so you can go find out why.

Special little edge case for you: if data is NULL, you just get zero back — and elf_errno is not set. that's it. that's the whole situation. 😭

---

🔥 SEE ALSO 🔥

• gelf_getauxv(3)
• getauxval(3)
• libelf(3)
• elf(5)

---

👑 ATTRIBUTES 👑

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

(translation: she's safe to call from multiple threads, go off queen)

---

💜 REPORTING BUGS 💜

Found a bug? Don't suffer in silence, tell the people:

• <elfutils-devel@sourceware.org>
• https://sourceware.org/bugzilla/

---

🧚 HISTORY 🧚

this section is empty in the original, so… nothing to report bestie, the history is giving silence 🌸

---

ok and for the little sign-off moment: this page is from Libelf, dated 2025-12-31, and it lives at GELF_UPDATE_AUXV(3). that's the whole page, you ate it, periodt 💅✨