NAME

       seccomp_syscall_priority - Prioritize syscalls in the seccomp filter

SYNOPSIS

       #include <seccomp.h>

       typedef void * scmp_filter_ctx;

       int SCMP_SYS(syscall_name);

       int seccomp_syscall_priority(scmp_filter_ctx ctx,
                                    int syscall, uint8_t priority);

       Link with -lseccomp.

DESCRIPTION

       The  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.

       While it is possible to specify the syscall value directly using the standard __NR_syscall
       values,  in  order  to  ensure proper operation across multiple architectures it is highly
       recommended to use the SCMP_SYS() macro instead.  See the EXAMPLES section below.

       The priority parameter takes an  8-bit  value  ranging  from  0  -  255;  a  higher  value
       represents a higher priority.

       The filter context ctx is the value returned by the call to seccomp_init().

RETURN VALUE

       The  SCMP_SYS()  macro  returns  a  value  suitable  for  use  as  the  syscall  value  in
       seccomp_syscall_priority().

       The seccomp_syscall_priority() function returns zero on success or one  of  the  following
       error codes on failure:

       -EDOM  Architecture specific failure.

       -EFAULT
              Internal libseccomp failure.

       -EINVAL
              Invalid input, either the context or architecture token is invalid.

       -ENOMEM
              The library was unable to allocate enough memory.

EXAMPLES

       #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;
       }

NOTES

       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.

       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.

AUTHOR

       Paul Moore <paul@paul-moore.com>

SEE ALSO

       seccomp_rule_add(3), seccomp_rule_add_exact(3)