# seccomp_syscall_priority

## 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.
    


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