[LTP] [PATCH v2] lib: tst_kconfig: Add runtime checks for CONFIG_*_NS

[LTP] [PATCH v2] lib: tst_kconfig: Add runtime checks for CONFIG_*_NS

[Cyril Hrubis]

Previously LTP Kconfig parsing logic only checked if a feature was
enabled during kernel compilation (e.g., CONFIG_USER_NS=y). However,
some kernel features can be compiled in but disabled at runtime via
kernel command-line or sysctls. Tests relying only on Kconfig variables
may have failed when features were runtime disabled.

This patch introduces a runtime check mechanism for Kconfig variables.
When a  CONFIG_* variable is parsed as 'y' or 'm' and when runtime check
has been associated with the variable we run the check and potentionaly
print a message and override the variable value.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
---
 lib/newlib_tests/test_kconfig.c |  1 +
 lib/tst_kconfig.c               | 38 ++++++++++++++++++++++++++++++++-
 lib/tst_kconfig_checks.h        | 37 ++++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+), 1 deletion(-)
 create mode 100644 lib/tst_kconfig_checks.h

diff --git a/lib/newlib_tests/test_kconfig.c b/lib/newlib_tests/test_kconfig.c
index cea36b5ee..ed2c4610a 100644
--- a/lib/newlib_tests/test_kconfig.c
+++ b/lib/newlib_tests/test_kconfig.c
@@ -18,6 +18,7 @@ static const char *kconfigs[] = {
 	"CONFIG_MMU & CONFIG_EXT4_FS=m",
 	"CONFIG_EXT4_FS=m | CONFIG_MMU",
 	"CONFIG_DEFAULT_HOSTNAME=\"(none)\"",
+	"CONFIG_USER_NS",
 	NULL
 };
 
diff --git a/lib/tst_kconfig.c b/lib/tst_kconfig.c
index adc56503e..52dd6d726 100644
--- a/lib/tst_kconfig.c
+++ b/lib/tst_kconfig.c
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
- * Copyright (c) 2018 Cyril Hrubis <chrubis@suse.cz>
+ * Copyright (c) 2018-2026 Cyril Hrubis <chrubis@suse.cz>
  */
 
 #include <stdlib.h>
@@ -16,6 +16,8 @@
 #include "tst_bool_expr.h"
 #include "tst_safe_stdio.h"
 
+#include "tst_kconfig_checks.h"
+
 static int kconfig_skip_check(void)
 {
 	char *skipped = getenv("KCONFIG_SKIP_CHECK");
@@ -110,6 +112,38 @@ static void close_kconfig(FILE *fp)
 		fclose(fp);
 }
 
+static struct runtime_check {
+	const char *config;
+	bool (*runtime_check)(void);
+} runtime_checks[] = {
+	{"CONFIG_USER_NS", tst_user_ns_enabled},
+	{"CONFIG_NET_NS", tst_net_ns_enabled},
+	{"CONFIG_PID_NS", tst_pid_ns_enabled},
+	{"CONFIG_MNT_NS", tst_mnt_ns_enabled},
+	{"CONFIG_IPC_NS", tst_ipc_ns_enabled},
+	{}
+};
+
+static void runtime_check(struct tst_kconfig_var *var)
+{
+	size_t i;
+
+	for (i = 0; runtime_checks[i].config; i++) {
+		if (strcmp(runtime_checks[i].config, var->id))
+			continue;
+
+		tst_res(TDEBUG, "Running runtime check for '%s'", var->id);
+
+		if (!runtime_checks[i].runtime_check()) {
+			tst_res(TINFO,
+				"%s=%c present but disabled at runtime",
+				var->id, var->choice);
+			var->choice = 'n';
+			return;
+		}
+	}
+}
+
 static inline int kconfig_parse_line(const char *line,
                                      struct tst_kconfig_var *vars,
                                      unsigned int vars_len)
@@ -183,9 +217,11 @@ out:
 			switch (val[0]) {
 			case 'y':
 				vars[i].choice = 'y';
+				runtime_check(&vars[i]);
 				return 1;
 			case 'm':
 				vars[i].choice = 'm';
+				runtime_check(&vars[i]);
 				return 1;
 			}
 		}
diff --git a/lib/tst_kconfig_checks.h b/lib/tst_kconfig_checks.h
new file mode 100644
index 000000000..94aad6411
--- /dev/null
+++ b/lib/tst_kconfig_checks.h
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 Cyril Hrubis <chrubis@suse.cz>
+ */
+
+#ifndef TST_KCONFIG_CHECKS_H
+#define TST_KCONFIG_CHECKS_H
+
+#include <unistd.h>
+#include <stdbool.h>
+
+static inline bool tst_user_ns_enabled(void)
+{
+	return access("/proc/self/ns/user", F_OK) == 0;
+}
+
+static inline bool tst_net_ns_enabled(void)
+{
+	return access("/proc/self/ns/net", F_OK) == 0;
+}
+
+static inline bool tst_pid_ns_enabled(void)
+{
+	return access("/proc/self/ns/pid", F_OK) == 0;
+}
+
+static inline bool tst_mnt_ns_enabled(void)
+{
+	return access("/proc/self/ns/mnt", F_OK) == 0;
+}
+
+static inline bool tst_ipc_ns_enabled(void)
+{
+	return access("/proc/self/ns/ipc", F_OK) == 0;
+}
+
+#endif /* TST_KCONFIG_CHECKS_H */
-- 
2.52.0


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Re: [LTP] [PATCH v2] lib: tst_kconfig: Add runtime checks for CONFIG_*_NS

[Li Wang via ltp]

On Wed, Apr 01, 2026 at 01:51:47PM +0200, Cyril Hrubis wrote:
> Previously LTP Kconfig parsing logic only checked if a feature was
> enabled during kernel compilation (e.g., CONFIG_USER_NS=y). However,
> some kernel features can be compiled in but disabled at runtime via
> kernel command-line or sysctls. Tests relying only on Kconfig variables
> may have failed when features were runtime disabled.
> 
> This patch introduces a runtime check mechanism for Kconfig variables.
> When a  CONFIG_* variable is parsed as 'y' or 'm' and when runtime check
> has been associated with the variable we run the check and potentionaly
> print a message and override the variable value.
> 
> Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
> Reviewed-by: Petr Vorel <pvorel@suse.cz>

Reviewed-by: Li Wang <liwang@redhat.com>

-- 
Regards,
Li Wang


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Re: [LTP] [PATCH v2] lib: tst_kconfig: Add runtime checks for CONFIG_*_NS

[Cyril Hrubis]

Hi!
Applied, thanks.

-- 
Cyril Hrubis
chrubis@suse.cz

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