SYSCALL_MODULE(9)

💅 SYSCALL_MODULE(9) 💅

okay bestie, welcome to the SYSCALL_MODULE(9) page from the Kernel Developer's Manual — yes, section 9, kernel-dev territory, main character energy only 👑. This is the whole syscall kernel module declaration macro situation, and we’re gonna get through every single detail together, fr fr 💖.

💖 NAME 💖

SYSCALL_MODULE — syscall kernel module declaration macro. periodt.

🌸 SYNOPSIS 🌸

copy this exactly, bestie, no vibes-based edits 💅:

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/module.h>
#include <sys/sysent.h>

SYSCALL_MODULE(name, int *offset, struct sysent *new_sysent,
    modeventhand_t evh, void *arg);

that’s the signature, and yes it’s giving very “kernel module declaration macro” ✨.

✨ DESCRIPTION ✨

SYSCALL_MODULE() declares a new syscall. It expands into a kernel module declaration with name sys/name — that’s the literal name pattern, iykyk 🦋.

The rest of the arguments expected by this macro are:

• offset — a pointer to an int which saves the offset in struct sysent where the syscall is allocated. If the location pointed to by offset holds a non 0 number it will be used if possible. If it holds 0 then one will be assigned. 💅
• new_sysent — a pointer to a structure that specifies the function implementing the syscall and the number of arguments this function needs (see <sys/sysent.h>). 🫶
• evh — a pointer to the kernel module event handler function with the argument arg. Please refer to module(9) for more information. 👑
• arg — the argument passed to the callback functions of the evh event handler when it is called. 🎀

The syscall number assigned to the module can be retrieved using the modstat(2) and modfind(2) system calls. The MACRO SYSCALL_MODULE_HELPER() includes SYSCALL_MODULE() and much of its boilerplate code. no cap, that helper is eating 😭🔥.

🎀 EXAMPLES 🎀

A minimal example for a syscall module can be found in /usr/share/examples/kld/syscall/module/syscall.c. literally the blueprint, bestie 🧚.

🦋 SEE ALSO 🦋

• module(9)
• /usr/share/examples/kld/syscall/module/syscall.c

💜 AUTHORS 💜

This manual page was written by Alexander Langer <alex@FreeBSD.org>. king behavior, honestly 👑.

💖 sign-off: source/version is Debian, dated June 15, 2023. mwah 💋