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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLES | NOTES | AUTHOR | SEE ALSO | COLOPHON |
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seccomp_attr_set(3) libseccomp Documentation seccomp_attr_set(3)
seccomp_attr_set, seccomp_attr_get - Manage the seccomp filter
attributes
#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.
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_init(3) or seccomp_reset(3).
The filter context ctx is the value returned by the call to
seccomp_init(3).
Valid attr values are as follows:
SCMP_FLTATR_ACT_DEFAULT
The default filter action as specified in the call to
seccomp_init(3) or seccomp_reset(3). This attribute is
read-only.
SCMP_FLTATR_ACT_BADARCH
The filter action taken when the loaded filter does not
match the architecture of the executing application.
Defaults to the SCMP_ACT_KILL action.
SCMP_FLTATR_CTL_NNP
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).
SCMP_FLTATR_CTL_TSYNC
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).
SCMP_FLTATR_API_TSKIP
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).
SCMP_FLTATR_CTL_LOG
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).
SCMP_FLTATR_CTL_SSB
A flag to disable Speculative Store Bypass mitigations for
this filter. Defaults to off (value == 0).
SCMP_FLTATR_CTL_OPTIMIZE
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.
SCMP_FLTATR_API_SYSRAWRC
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).
SCMP_FLTATR_CTL_WAITKILL
A flag to specify if libseccomp should request wait
killable semantics when possible. Defaults to off (value
== 0).
Returns zero on success or one of the following error codes on
failure:
-EACCES
Setting the attribute with the given value is not allowed.
-EEXIST
The attribute does not exist.
-EINVAL
Invalid input, either the context or architecture token is
invalid.
-EOPNOTSUPP
The library doesn't support the particular operation.
#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;
/* ... */
out:
seccomp_release(ctx);
return -rc;
}
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.
Paul Moore <paul@paul-moore.com>
seccomp_init(3), seccomp_reset(3), seccomp_load(3), seccomp(2)
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 ⟨https://github.com/seccomp/libseccomp⟩. If you
have a bug report for this manual page, see
⟨https://groups.google.com/d/forum/libseccomp⟩. This page was
obtained from the project's upstream Git repository
⟨https://github.com/seccomp/libseccomp⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-05-09.) 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
man-pages@man7.org
paul@paul-moore.com 21 September 2022 seccomp_attr_set(3)
Pages that refer to this page: seccomp_merge(3), seccomp_rule_add(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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