Tilck supports both the int 0x80 syscall interface and the sysenter one.
Here below there is an up-to-date table containing the status of each supported
syscall at the moment. Because the list of the not-yet-supported syscalls is
much longer than the list of supported ones, the table below mentions only the
syscalls having some degree of support. The missing syscalls have to be
considered as not implemented yet.
| Syscall | Support level |
|---|---|
| sys_exit | full |
| sys_fork | full |
| sys_read | full |
| sys_write | full |
| sys_open | partial++ [1] |
| sys_close | full |
| sys_waitpid | full |
| sys_execve | full |
| sys_chdir | full |
| sys_getpid | full |
| sys_setuid16 | limited [3] |
| sys_getuid16 | limited [3] |
| sys_pause | minimal [2] |
| sys_access | partial |
| sys_brk | full |
| sys_setgid16 | limited [3] |
| sys_getgid16 | limited [3] |
| sys_seteuid16 | limited [3] |
| sys_setegid16 | limited [3] |
| sys_geteuid16 | limited [3] |
| sys_getegid16 | limited [3] |
| sys_ioctl | partial |
| sys_getppid | full |
| sys_gettimeofday | full |
| sys_munmap | full |
| sys_wait4 | full |
| sys_newuname | full |
| sys_llseek | full |
| sys_readv | full |
| sys_writev | full |
| sys_nanosleep_time32 | full |
| sys_prctl | stub |
| sys_getcwd | full |
| sys_mmap_pgoff | full |
| sys_stat64 | full |
| sys_fstat64 | full |
| sys_lstat64 | partial |
| sys_getuid | limited [3] |
| sys_getgid | limited [3] |
| sys_geteuid | limited [3] |
| sys_getegid | limited [3] |
| sys_setuid | limited [3] |
| sys_setgid | limited [3] |
| sys_getdents64 | full |
| sys_fcntl64 | partial |
| sys_gettid | minimal [4] |
| sys_set_thread_area | full |
| sys_exit_group | minimal [5] |
| sys_set_tid_address | stub |
| sys_tkill | partial++ [6] |
| sys_tgkill | partial++ [6] |
| sys_kill | full |
| sys_setsid | full |
| sys_times | minimal [9] |
| sys_clock_gettime | compliant [10] |
| sys_clock_gettime32 | compliant [10] |
| sys_clock_getres | compliant [10] |
| sys_clock_getres_time32 | compliant [10] |
| sys_select | full |
| sys_poll | full |
| sys_readlink | full |
| sys_creat | full |
| sys_unlink | full |
| sys_symlink | full |
| sys_pread64 | full |
| sys_pwrite64 | full |
| sys_vfork | compliant [11] |
| sys_umask | full |
| sys_ia32_truncate64 | full |
| sys_ia32_ftruncate64 | full |
| sys_sync | full |
| sys_syncfs | full |
| sys_chown | limited [3] |
| sys_fchown | limited [3] |
| sys_lchown | limited [3] |
| sys_chmod | full |
| sys_fchmod | full |
| sys_rename | full |
| sys_link | full |
| sys_pipe | full |
| sys_pipe2 | partial++ [13] |
| sys_sched_yield | full |
| sys_getsid | full |
| sys_setpgid | full |
| sys_getpgid | full |
| sys_getpgrp | full |
| sys_utime32 | full |
| sys_utimes | full |
| sys_fsync | compliant |
| sys_fdatasync | compliant |
| sys_dup | full |
| sys_dup2 | full |
| sys_reboot | full |
| sys_rt_sigprocmask | full |
| sys_rt_sigpending | full |
| sys_rt_sigreturn | partial [14] |
| sys_rt_sigaction | partial [14] |
| sys_rt_sigsuspend | partial [14] |
Definitions:
| Support level | Meaning |
|---|---|
| full | Syscall 100% supported. |
| partial | Syscall partially supported, work-in-progress |
| partial++ | All of the really important flags and modes are supported |
| ... | Most of the advanced stuff very likely is still not supported. |
| stub | The syscall does not return -ENOSYS, but it has actually a stub |
| ... | implementation, at the moment. |
| minimal | Like partial, just even less features are supported |
| compliant | Syscall supported in a way compliant with a full |
| ... | implementation, but actually it has several limitations due to |
| ... | the different design of Tilck. Example: see the note [3]. |
| limited | The syscall supports by design only a subset of the cases |
| ... | supported by the Linux implementation. |
Notes:
-
The syscall open() now supports read/write access, file creation, mode setting and flags like O_APPEND, O_CLOEXEC, O_EXCL, O_TRUNC. All the "advanced" flags like O_ASYNC are not supported yet.
-
Because custom signal handlers are not supported, pause() puts the process to sleep until a signal actually kills it.
-
Tilck does not support by design multiple users nor any form of authentication. Therefore, the following statement is always true: UID == GID == EUID == EGID == 0. All the calls like setuid(), seteuid(), setgid(), setegid(), chown() etc. succeed only when UID/GID == 0.
-
Because the lack of thread support,
gettid()is the same asgetpid() -
Because the lack of thread support, exit_group() behaves as exit()
-
Because the lack of thread support,
tgkill()works only whentgid==tid. -
[Limitation removed]
-
[Limitation removed]
-
At the moment
times()just updatestms_utimeandtms_stime. -
Only the clocks CLOCK_REALTIME and CLOCK_MONOTONIC are supported.
-
Behaves exactly as
fork(). -
[Limitation removed]
-
The O_DIRECT mode is not supported.
-
Tilck has a partial support for POSIX signals. SIG_IGN and SIG_DFL are fully supported. Custom signal handlers are supported as well, but signal handlers (even of different type) cannot interrupt each other. In other words, nested custom signal handlers are not supported, yet. Also, even if the modern sys_rt_sigaction() interface is implemented, none of its flags like SA_NODEFER, SA_ONSTACK, SA_RESETHAND, SA_RESTART, SA_SIGINFO are supported, at the moment. The per-signal sa_mask is also fixed: while a custom handler is running, all the other signals having a custom handler are masked (terminating signals instead, can always we delieved). In addition, the order of delivery of all signals is unspecified and there is no distinction between regular signals and real-time ones. Also, at the moment, no syscall can be restarted if a signal interrupted it. The syscall sys_rt_sigsuspend() works as expected if we're not calling it from a signal handler otherwise, it returns -EPERM (not allowed according to POSIX).
NOTE: while the just-described limited support for POSIX reliable signals might seem too limited, it's worth noting that it already opened a considerable amount of uses, like graceful process termination with SIGTERM.