KLDSYM(2)

💖 KLDSYM 💖

okay bestie, section 2 of the manual, kldsym — say it with me, it's a system call, we're in the syscall girlies now 💅

---

✨ NAME ✨

kldsym — look up address by symbol name in a KLD

---

🫶 LIBRARY 🫶

Standard C Library (libc, -lc)

no cap, it's right there in libc, you don't need anything extra

---

🌸 SYNOPSIS 🌸

#include <sys/param.h>
#include <sys/linker.h>

int
kldsym(int fileid, int cmd, void *data);

---

👑 DESCRIPTION 👑

so the kldsym() system call is the one you call when you're like "hey, what's the address of this symbol?" — it returns the address of the symbol specified in data, inside the module specified by fileid. ✨

and here's the cute part: if fileid is 0, all the loaded modules get searched. every single one. she's thorough like that 💅

right now, the only cmd that's actually implemented is KLDSYM_LOOKUP. that's it. that's the whole menu. periodt.

---

🎀 the data argument 🎀

data is a pointer to this structure, exactly this one:

struct kld_sym_lookup {
    int         version;        /* sizeof(struct kld_sym_lookup) */
    char        *symname;       /* Symbol name we are looking up */
    u_long      symvalue;
    size_t      symsize;
};

okay so here's the vibe of each member 🦋

• version — you set this one, bestie. and you set it to sizeof(struct kld_sym_lookup). don't get creative with it.
• the next two members, version and symname, are specified by the user. (yes, the page says version again — I'm just telling you what she said 🙈)
• symvalue and symsize — these two get filled in for you by kldsym(). symvalue holds the address associated with symname, and symsize holds the size of the data it points to. respectively. iconic. 💖

so you bring the name, she brings the address and the size. it's giving collaborative. it's giving teamwork. 🌈

---

🔥 RETURN VALUES 🔥

• returns the value 0 if successful — slay 💅
• otherwise the value -1 is returned and the global variable errno is set to indicate the error. (she'll tell you what went wrong, just read the vibe check) 😭

---

💀 ERRORS 💀

the kldsym() system call will fail if:

• [EINVAL] — Invalid value in data->version or cmd. 🚩
• [ENOENT] — The fileid argument is invalid, or the specified symbol could not be found. she looked. she really looked. it's not there. 🫠

---

🌟 SEE ALSO 🌟

kldfind(2), kldfirstmod(2), kldload(2), kldnext(2), kldunload(2), modfind(2), modnext(2), modstat(2), kld(4)

the whole friend group fr fr, go read them all 🫶

---

📜 HISTORY 📜

The kldsym() system call first appeared in FreeBSD 3.0. she's been around a minute, she's a legend, she's an icon, and she is the moment 👑

---

kdl moment: set version to sizeof(struct kld_sym_lookup) before you call, or you're gonna have a bad time. no cap. 💀

---

and that's the whole page, bestie!! 💖 this one came from the Debian crew, dated October 17, 2016, and yeah it lives at KLDSYM(2) — section 2, system calls, exactly where she belongs. go forth and look up some symbols, i'm obsessed with you 🎀✨🦋