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)

paul@paul-moore.com                                30 May 2020                       seccomp_syscall_priority(3)