https://elixir.bootlin.com/linux/v5.14.13/source/fs/open.c#L1224

syscalls-macro.h

/* https://elixir.bootlin.com/linux/v5.14.13/source/fs/open.c#L1224 */
SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
{
    if (force_o_largefile())
        flags |= O_LARGEFILE;
    return do_sys_open(AT_FDCWD, filename, flags, mode);
}

/* /include/linux/syscalls.h::SYSCALL_DEFINE3 */
#define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name, __VA_ARGS__)

/* /include/linux/syscalls.h::SYSCALL_DEFINEx */
#define SYSCALL_DEFINEx(x, sname, ...)              \
    __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
#endif

/* /include/linux/syscalls.h::__SYSCALL_DEFINEx */
#define __SYSCALL_DEFINEx(x, name, ...)                 \
    asmlinkage long sys##name(__SC_DECL##x(__VA_ARGS__));       \
    static inline long SYSC##name(__SC_DECL##x(__VA_ARGS__));   \
    asmlinkage long SyS##name(__SC_LONG##x(__VA_ARGS__))        \
    {                               \
        __SC_TEST##x(__VA_ARGS__);              \
        return (long) SYSC##name(__SC_CAST##x(__VA_ARGS__));    \
    }                               \
    SYSCALL_ALIAS(sys##name, SyS##name);                \
    static inline long SYSC##name(__SC_DECL##x(__VA_ARGS__))