shared: add @known syscall list

man/systemd.exec.xml

@@ -1933,6 +1933,10 @@ RestrictNamespaces=~cgroup net</programlisting>
                 <entry>@timer</entry>
                 <entry>System calls for scheduling operations by time (<citerefentry project='man-pages'><refentrytitle>alarm</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>timer_create</refentrytitle><manvolnum>2</manvolnum></citerefentry>, …)</entry>
               </row>
+              <row>
+                <entry>@known</entry>
+                <entry>All system calls defined by the kernel. This list is defined statically in systemd based on a kernel version that was available when this systmed version was released. It will become progressively more out-of-date as the kernel is updated.</entry>
+              </row>
             </tbody>
           </tgroup>
         </table>

src/shared/generate-syscall-list.py

@@ -0,0 +1,5 @@
+#!/usr/bin/env python
+import sys
+
+for line in open(sys.argv[1]):
+    print('"{}\\0"'.format(line.strip()))

src/shared/meson.build

@@ -262,6 +262,16 @@ endif
 test_tables_h = files('test-tables.h')
 shared_sources += test_tables_h
 
+generate_syscall_list = find_program('generate-syscall-list.py')
+fname = 'syscall-list.h'
+syscall_list_h = custom_target(
+        fname,
+        input : 'syscall-names.text',
+        output : fname,
+        command : [generate_syscall_list,
+                   '@INPUT@'],
+        capture : true)
+
 if conf.get('HAVE_ACL') == 1
         shared_sources += files('acl-util.c')
 endif
@@ -272,6 +282,7 @@ endif
 
 if conf.get('HAVE_SECCOMP') == 1
         shared_sources += files('seccomp-util.c')
+        shared_sources += syscall_list_h
 endif
 
 if conf.get('HAVE_LIBIPTC') == 1

src/shared/seccomp-util.c

@@ -883,6 +883,12 @@ const SyscallFilterSet syscall_filter_sets[_SYSCALL_FILTER_SET_MAX] = {
                 "timerfd_settime64\0"
                 "times\0"
         },
+        [SYSCALL_FILTER_SET_KNOWN] = {
+                .name = "@known",
+                .help = "All known syscalls declared in the kernel",
+                .value =
+#include "syscall-list.h"
+        },
 };
 
 const SyscallFilterSet *syscall_filter_set_find(const char *name) {

src/shared/seccomp-util.h

@@ -21,7 +21,7 @@ typedef struct SyscallFilterSet {
 } SyscallFilterSet;
 
 enum {
-        /* Please leave DEFAULT first, but sort the rest alphabetically */
+        /* Please leave DEFAULT first and KNOWN last, but sort the rest alphabetically */
         SYSCALL_FILTER_SET_DEFAULT,
         SYSCALL_FILTER_SET_AIO,
         SYSCALL_FILTER_SET_BASIC_IO,
@@ -50,6 +50,7 @@ enum {
         SYSCALL_FILTER_SET_SYNC,
         SYSCALL_FILTER_SET_SYSTEM_SERVICE,
         SYSCALL_FILTER_SET_TIMER,
+        SYSCALL_FILTER_SET_KNOWN,
         _SYSCALL_FILTER_SET_MAX
 };
 

src/test/test-seccomp.c

@@ -121,7 +121,9 @@ static void test_filter_sets(void) {
                         int fd, r;
 
                         /* If we look at the default set (or one that includes it), allow-list instead of deny-list */
-                        if (IN_SET(i, SYSCALL_FILTER_SET_DEFAULT, SYSCALL_FILTER_SET_SYSTEM_SERVICE))
+                        if (IN_SET(i, SYSCALL_FILTER_SET_DEFAULT,
+                                      SYSCALL_FILTER_SET_SYSTEM_SERVICE,
+                                      SYSCALL_FILTER_SET_KNOWN))
                                 r = seccomp_load_syscall_filter_set(SCMP_ACT_ERRNO(EUCLEAN), syscall_filter_sets + i, SCMP_ACT_ALLOW, true);
                         else
                                 r = seccomp_load_syscall_filter_set(SCMP_ACT_ALLOW, syscall_filter_sets + i, SCMP_ACT_ERRNO(EUCLEAN), true);
@@ -145,22 +147,25 @@ static void test_filter_sets(void) {
 }
 
 static void test_filter_sets_ordered(void) {
-        size_t i;
-
         log_info("/* %s */", __func__);
 
         /* Ensure "@default" always remains at the beginning of the list */
         assert_se(SYSCALL_FILTER_SET_DEFAULT == 0);
         assert_se(streq(syscall_filter_sets[0].name, "@default"));
 
-        for (i = 0; i < _SYSCALL_FILTER_SET_MAX; i++) {
+        /* Ensure "@known" always remains at the end of the list */
+        assert_se(SYSCALL_FILTER_SET_KNOWN == _SYSCALL_FILTER_SET_MAX - 1);
+        assert_se(streq(syscall_filter_sets[SYSCALL_FILTER_SET_KNOWN].name, "@known"));
+
+        for (size_t i = 0; i < _SYSCALL_FILTER_SET_MAX; i++) {
                 const char *k, *p = NULL;
 
                 /* Make sure each group has a description */
                 assert_se(!isempty(syscall_filter_sets[0].help));
 
-                /* Make sure the groups are ordered alphabetically, except for the first entry */
-                assert_se(i < 2 || strcmp(syscall_filter_sets[i-1].name, syscall_filter_sets[i].name) < 0);
+                /* Make sure the groups are ordered alphabetically, except for the first and last entries */
+                assert_se(i < 2 || i == _SYSCALL_FILTER_SET_MAX - 1 ||
+                          strcmp(syscall_filter_sets[i-1].name, syscall_filter_sets[i].name) < 0);
 
                 NULSTR_FOREACH(k, syscall_filter_sets[i].value) {