seccomp_attr_set(3) — Linux manual page


seccomp_attr_set(3)     libseccomp Documentation     seccomp_attr_set(3)

NAME         top

       seccomp_attr_set, seccomp_attr_get - Manage the seccomp filter

SYNOPSIS         top

       #include <seccomp.h>

       typedef void * scmp_filter_ctx;
       enum scmp_filter_attr;

       int seccomp_attr_set(scmp_filter_ctx ctx,
                            enum scmp_filter_attr attr, uint32_t value);
       int seccomp_attr_get(scmp_filter_ctx ctx,
                            enum scmp_filter_attr attr, uint32_t *value);

       Link with -lseccomp.

DESCRIPTION         top

       The seccomp_attr_set() function sets the different seccomp filter
       attributes while the seccomp_attr_get() function fetches the
       filter attributes.  The seccomp filter attributes are tunable
       values that affect how the library behaves when generating and
       loading the seccomp filter into the kernel.  The attributes are
       reset to their default values whenever the filter is initialized
       or reset via seccomp_filter_init(3) or seccomp_filter_reset(3).

       The filter context ctx is the value returned by the call to

       Valid attr values are as follows:

              The default filter action as specified in the call to
              seccomp_filter_init(3) or seccomp_filter_reset(3).  This
              attribute is read-only.

              The filter action taken when the loaded filter does not
              match the architecture of the executing application.
              Defaults to the SCMP_ACT_KILL action.

              A flag to specify if the NO_NEW_PRIVS functionality should
              be enabled before loading the seccomp filter into the
              kernel.  Setting this to off ( value == 0) results in no
              action, meaning that loading the seccomp filter into the
              kernel will fail if CAP_SYS_ADMIN is missing and
              NO_NEW_PRIVS has not been externally set.  Defaults to on
              ( value == 1).

              A flag to specify if the kernel should attempt to
              synchronize the filters across all threads on
              seccomp_load(3).  If the kernel is unable to synchronize
              all of the thread then the load operation will fail.  This
              flag is only available on Linux Kernel 3.17 or greater;
              attempting to enable this flag on earlier kernels will
              result in an error being returned.  Defaults to off (
              value == 0).

              A flag to specify if libseccomp should allow filter rules
              to be created for the -1 syscall.  The -1 syscall value
              can be used by tracer programs to skip specific syscall
              invocations, see seccomp(2) for more information.
              Defaults to off ( value == 0).

              A flag to specify if the kernel should log all filter
              actions taken except for the SCMP_ACT_ALLOW action.
              Defaults to off ( value == 0).

              A flag to disable Speculative Store Bypass mitigations for
              this filter.  Defaults to off ( value == 0).

              A flag to specify the optimization level of the seccomp
              filter.  By default libseccomp generates a set of
              sequential ´if´ statements for each rule in the filter.
              seccomp_syscall_priority(3) can be used to prioritize the
              order for the default cause.  The binary tree optimization
              sorts by syscall numbers and generates consistent O(log n)
              filter traversal for every rule in the filter.  The binary
              tree may be advantageous for large filters.  Note that
              seccomp_syscall_priority(3) is ignored when
              SCMP_FLTATR_CTL_OPTIMIZE == 2.

              The different optimization levels are described below:

              0      Reserved value, not currently used.

              1      Rules sorted by priority and complexity (DEFAULT).

              2      Binary tree sorted by syscall number.

              A flag to specify if libseccomp should pass system error
              codes back to the caller instead of the default
              -ECANCELED.  Defaults to off ( value == 0).

RETURN VALUE         top

       Returns zero on success or one of the following error codes on

              Setting the attribute with the given value is not allowed.

              The attribute does not exist.

              Invalid input, either the context or architecture token is

              The library doesn't support the particular operation.

EXAMPLES         top

       #include <seccomp.h>

       int main(int argc, char *argv[])
            int rc = -1;
            scmp_filter_ctx ctx;

            ctx = seccomp_init(SCMP_ACT_ALLOW);
            if (ctx == NULL)
                 goto out;

            /* ... */

            rc = seccomp_attr_set(ctx, SCMP_FLTATR_ACT_BADARCH, SCMP_ACT_TRAP);
            if (rc < 0)
                 goto out;

            /* ... */

            return -rc;

NOTES         top

       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  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         top

       Paul Moore <>

SEE ALSO         top

       seccomp_init(3), seccomp_reset(3), seccomp_load(3), seccomp(2)

COLOPHON         top

       This page is part of the libseccomp (high-level API to the Linux
       Kernel's seccomp filter) project.  Information about the project
       can be found at ⟨⟩.  If you
       have a bug report for this manual page, see
       ⟨⟩.  This page was
       obtained from the project's upstream Git repository
       ⟨⟩ on 2021-08-27.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-08-25.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to           06 June 2020           seccomp_attr_set(3)

Pages that refer to this page: seccomp_merge(3)seccomp_rule_add(3)