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diff --git a/static/openbsd/man9/syscall.9 b/static/openbsd/man9/syscall.9 new file mode 100644 index 00000000..32bad940 --- /dev/null +++ b/static/openbsd/man9/syscall.9 @@ -0,0 +1,244 @@ +.\" $OpenBSD: syscall.9,v 1.16 2023/12/13 06:39:10 jmc Exp $ +.\" +.\" Copyright (c) 2003 Michael Shalayeff +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF MIND, USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.Dd $Mdocdate: December 13 2023 $ +.Dt SYSCALL 9 +.Os +.Sh NAME +.Nm syscall +.Nd system calls overview +.Sh DESCRIPTION +System calls in the kernel are implemented through a set of +switch tables for each emulation type. +Each table is generated from the +.Dq master +file by +.Pa sys/kern/makesyscalls.sh +through the appropriate rules in the +.Pa Makefile . +.Pp +The +.Dq master +file is a text file consisting of a list of lines for each +system call. +Lines may be split by the means of back slashing the end of the line. +Each line is a set of fields separated by whitespace: +.Pp +.D1 Cd number type ... +.Pp +Where: +.Bl -tag -width number -compact +.It number +is the system call number; +.It type +is one of: +.Bl -tag -width COMPAT_XXX -compact +.It STD +always included; +.It OBSOL +obsolete, not included in the system; +.It UNIMPL +unimplemented, not included in the system; +.It NODEF +included, but don't define the syscall number; +.It NOARGS +included, but don't define the syscall args structure; +.It INDIR +included, but don't define the syscall args structure, +and allow it to be "really" varargs; +.It COMPAT_XX +a compatibility system call, only included if the corresponding +option is configured for the kernel (see +.Xr options 4 ) . +.El +.El +.Pp +The rest of the line for the STD, NODEF, NOARGS, and COMPAT_XX +types is: +.Pp +.D1 Cd { pseudo-proto } [alias] +.Pp +.Nm pseudo-proto +is a C-like prototype used to generate the system call argument list, +and alias is an optional name alias for the call. +The function in the prototype has to be defined somewhere in +the kernel sources as it will be used as an entry point for +the corresponding system call. +.Pp +For other types the rest of the line is a comment. +.Pp +To generate the header and code files from the +.Dq master +file a +.Xr make 1 +command has to be run from the directory containing the +.Dq master +file. +.Ss Usage +Entry from the user space for the system call is machine dependent. +Typical code to invoke a system call from the machine dependent +sources might look like this: +.Bd -literal -offset indent + + const struct sysent *callp; + register_t code, args[8], rval[2]; + struct proc *p = curproc; + int code, nsys; + +\&... + +/* "code" is the system call number passed from the user space */ + +\&... + +if (code < 0 || code >= nsys) + callp += p->p_emul->e_nosys; /* illegal */ +else + callp += code; + +/* copyin the arguments from the user space */ +\&... + rval[0] = 0; + +/* the following steps are now performed using mi_syscall() */ +#ifdef SYSCALL_DEBUG + scdebug_call(p, code, args); +#endif +#ifdef KTRACE + if (KTRPOINT(p, KTR_SYSCALL)) + ktrsyscall(p, code, argsize, args); +#endif + error = (*callp->sy_call)(p, args, rval); + + switch (error) { + case 0: + /* normal return */ + \&... + break; + case ERESTART: + /* + * adjust PC to point before the system call + * in the user space in order for the return + * back there we reenter the kernel to repeat + * the same system call + */ + \&... + break; + case EJUSTRETURN: + /* just return */ + break; + default: + /* + * an error returned: + * call an optional emulation errno mapping + * routine and return back to the user. + */ + if (p->p_emul->e_errno) + error = p->p_emul->e_errno[error]; + \&... + break; + } + +/* the following steps are now performed using mi_syscall_return() */ +#ifdef SYSCALL_DEBUG + scdebug_ret(p, code, orig_error, rval); +#endif + userret(p); +#ifdef KTRACE + if (KTRPOINT(p, KTR_SYSRET)) + ktrsysret(p, code, orig_error, rval[0]); +#endif + +.Ed +.Pp +The +.Dv SYSCALL_DEBUG +parts of the code are explained in the +.Sx Debugging +section below. +For the +.Dv KTRACE +portions of the code refer to the +.Xr ktrace 9 +document for further explanations. +.Ss Debugging +For debugging purposes the line +.Pp +.D1 Cd option SYSCALL_DEBUG +.Pp +should be included in the kernel configuration file (see +.Xr options 4 ) . +This allows tracing for calls, returns, and arguments for both +implemented and non-implemented system calls. +A global integer variable +.Va scdebug +contains a mask for the desired logging events: +.Pp +.Bl -tag -width SCDEBUG_SHOWARGS__ -compact +.It SCDEBUG_CALLS +(0x0001) show calls; +.It SCDEBUG_RETURNS +(0x0002) show returns; +.It SCDEBUG_ALL +(0x0004) show even syscalls that are implemented; +.It SCDEBUG_SHOWARGS +(0x0008) show arguments to calls. +.El +.Pp +Use +.Xr ddb 4 +to set +.Va scdebug +to the desired value. +.Sh CODE REFERENCES +.Bl -tag -width sys/kern/syscalls.master -compact +.It Pa sys/kern/makesyscalls.sh +a +.Xr sh 1 +script for generating C files out of the syscall master file; +.It Pa sys/kern/syscalls.conf +a configuration file for the shell script above; +.It Pa sys/kern/syscalls.master +master files describing names and numbers for the system calls; +.It Pa sys/kern/syscalls.c +system call names lists; +.It Pa sys/kern/init_sysent.c +system call switch tables; +.It Pa sys/sys/syscallargs.h +system call argument lists; +.It Pa sys/sys/syscall.h +system call numbers; +.It Pa sys/sys/syscall_mi.h +Machine-independent syscall entry end return handling. +.El +.Sh SEE ALSO +.Xr ktrace 2 , +.Xr ktrace 9 , +.Xr sysctl_int 9 +.Sh HISTORY +The +.Nm +section manual page appeared in +.Ox 3.4 . |