Hi Michael, AFAICT, the syscalls [rt_]sigprocmask use '[old_]sigset_t' (there's the '__user' modifier too), so 'kernel_' should be removed from the types, shouldn't it? Thanks, Alex [[ SYNOPSIS #include <signal.h> /* Prototype for the glibc wrapper function */ int sigprocmask(int how, const sigset_t *restrict set, sigset_t *restrict oldset); /* Prototype for the underlying system call */ int rt_sigprocmask(int how, const kernel_sigset_t *set, kernel_sigset_t *oldset, size_t sigsetsize); /* Prototype for the legacy system call (deprecated) */ int sigprocmask(int how, const old_kernel_sigset_t *set, old_kernel_sigset_t *oldset); Feature Test Macro Requirements for glibc (see fea‐ ture_test_macros(7)): sigprocmask(): _POSIX_C_SOURCE ]] .../linux$ grep_syscall rt_sigprocmask kernel/signal.c:3050: SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, nset, sigset_t __user *, oset, size_t, sigsetsize) kernel/signal.c:3081: COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset, compat_sigset_t __user *, oset, compat_size_t, sigsetsize) include/linux/compat.h:698: asmlinkage long compat_sys_rt_sigprocmask(int how, compat_sigset_t __user *set, compat_sigset_t __user *oset, compat_size_t sigsetsize); include/linux/syscalls.h:696: asmlinkage long sys_rt_sigprocmask(int how, sigset_t __user *set, sigset_t __user *oset, size_t sigsetsize); .../linux$ grep_syscall sigprocmask kernel/compat.c:40: COMPAT_SYSCALL_DEFINE3(sigprocmask, int, how, compat_old_sigset_t __user *, nset, compat_old_sigset_t __user *, oset) kernel/signal.c:4236: SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, nset, old_sigset_t __user *, oset) include/linux/compat.h:882: asmlinkage long compat_sys_sigprocmask(int how, compat_old_sigset_t __user *nset, compat_old_sigset_t __user *oset); include/linux/syscalls.h:1136: asmlinkage long sys_sigprocmask(int how, old_sigset_t __user *set, old_sigset_t __user *oset); .../linux$ -- Alejandro Colomar Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/ http://www.alejandro-colomar.es/