Bundle libseccomp 2.3.1

[linux-seccomp.git] / libseccomp / doc / man / man3 / seccomp_syscall_priority.3

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+.TH "seccomp_syscall_priority" 3 "25 July 2012" "paul@paul-moore.com" "libseccomp Documentation"
+.\" //////////////////////////////////////////////////////////////////////////
+.SH NAME
+.\" //////////////////////////////////////////////////////////////////////////
+seccomp_syscall_priority \- Prioritize syscalls in the seccomp filter
+.\" //////////////////////////////////////////////////////////////////////////
+.SH SYNOPSIS
+.\" //////////////////////////////////////////////////////////////////////////
+.nf
+.B #include <seccomp.h>
+.sp
+.B typedef void * scmp_filter_ctx;
+.sp
+.BI "int SCMP_SYS(" syscall_name ");"
+.sp
+.BI "int seccomp_syscall_priority(scmp_filter_ctx " ctx ","
+.BI "                             int " syscall ", uint8_t " priority ");"
+.sp
+Link with \fI\-lseccomp\fP.
+.fi
+.\" //////////////////////////////////////////////////////////////////////////
+.SH DESCRIPTION
+.\" //////////////////////////////////////////////////////////////////////////
+.P
+The
+.BR seccomp_syscall_priority ()
+function provides a priority hint to the seccomp filter generator in libseccomp
+such that higher priority syscalls are placed earlier in the seccomp filter code
+so that they incur less overhead at the expense of lower priority syscalls.  A
+syscall's priority can be set regardless of if any rules currently exist for
+that syscall; the library will remember the priority and it will be assigned to
+the syscall if and when a rule for that syscall is created.
+.P
+While it is possible to specify the
+.I syscall
+value directly using the standard
+.B __NR_syscall
+values, in order to ensure proper operation across multiple architectures it
+is highly recommended to use the
+.BR SCMP_SYS ()
+macro instead.  See the EXAMPLES section below.
+.P
+The
+.I priority
+parameter takes an 8-bit value ranging from 0 \- 255; a higher value represents
+a higher priority.
+.P
+The filter context
+.I ctx
+is the value returned by the call to
+.BR seccomp_init ().
+.\" //////////////////////////////////////////////////////////////////////////
+.SH RETURN VALUE
+.\" //////////////////////////////////////////////////////////////////////////
+The
+.BR seccomp_syscall_priority ()
+function returns zero on success, negative errno values on failure.  The
+.BR SCMP_SYS ()
+macro returns a value suitable for use as the
+.I syscall
+value in
+.BR seccomp_syscall_priority ().
+.\" //////////////////////////////////////////////////////////////////////////
+.SH EXAMPLES
+.\" //////////////////////////////////////////////////////////////////////////
+.nf
+#include <seccomp.h>
+
+int main(int argc, char *argv[])
+{
+       int rc = \-1;
+       scmp_filter_ctx ctx;
+
+       ctx = seccomp_init(SCMP_ACT_KILL);
+       if (ctx == NULL)
+               goto out;
+
+       /* ... */
+
+       rc = seccomp_syscall_priority(ctx, SCMP_SYS(read), 200);
+       if (rc < 0)
+               goto out;
+
+       /* ... */
+
+out:
+       seccomp_release(ctx);
+       return \-rc;
+}
+.fi
+.\" //////////////////////////////////////////////////////////////////////////
+.SH NOTES
+.\" //////////////////////////////////////////////////////////////////////////
+.P
+While the seccomp filter can be generated independent of the kernel, kernel
+support is required to load and enforce the seccomp filter generated by
+libseccomp.
+.P
+The libseccomp project site, with more information and the source code
+repository, can be found at https://github.com/seccomp/libseccomp.  This tool,
+as well as the libseccomp library, is currently under development, please
+report any bugs at the project site or directly to the author.
+.\" //////////////////////////////////////////////////////////////////////////
+.SH AUTHOR
+.\" //////////////////////////////////////////////////////////////////////////
+Paul Moore <paul@paul-moore.com>
+.\" //////////////////////////////////////////////////////////////////////////
+.SH SEE ALSO
+.\" //////////////////////////////////////////////////////////////////////////
+.BR seccomp_rule_add (3),
+.BR seccomp_rule_add_exact (3)