[LTP] [PATCH v2] syscall02: test invalid syscall number -1

[LTP] [PATCH v2] syscall02: test invalid syscall number -1

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

Add a test verifying that a raw syscall() with the reserved number -1
fails with ENOSYS. The behavior is architecture specific, so the test is
limited to the architectures where it was checked against kernel code.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
Changes in v2:
- update imports and description
- Link to v1: https://lore.kernel.org/20260714-syscall_invalid_nr-v1-1-d8b6f4e3ec7b@suse.com
---
 runtest/syscalls                              |  1 +
 testcases/kernel/syscalls/syscall/.gitignore  |  1 +
 testcases/kernel/syscalls/syscall/syscall02.c | 31 +++++++++++++++++++++++++++
 3 files changed, 33 insertions(+)

diff --git a/runtest/syscalls b/runtest/syscalls
index a021c79da49d4157c33187caed2dd3f0483759e0..8a777e61da1af59ba694e0bc5b5d92bb1d63754a 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -1678,6 +1678,7 @@ sync_file_range01 sync_file_range01
 sync_file_range02 sync_file_range02
 
 syscall01 syscall01
+syscall02 syscall02
 
 sysconf01 sysconf01
 
diff --git a/testcases/kernel/syscalls/syscall/.gitignore b/testcases/kernel/syscalls/syscall/.gitignore
index 74a081e40cb564e874e0f81478d3d1a0e95b6df4..fed1d81079450a7442023447285cd112924f7a10 100644
--- a/testcases/kernel/syscalls/syscall/.gitignore
+++ b/testcases/kernel/syscalls/syscall/.gitignore
@@ -1 +1,2 @@
 /syscall01
+/syscall02
diff --git a/testcases/kernel/syscalls/syscall/syscall02.c b/testcases/kernel/syscalls/syscall/syscall02.c
new file mode 100644
index 0000000000000000000000000000000000000000..2fefcb17c763813653a6644759c2a035bee2c604
--- /dev/null
+++ b/testcases/kernel/syscalls/syscall/syscall02.c
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 SUSE LLC Andrea Cervesato <andrea.cervesato@suse.com>
+ */
+
+/*\
+ * Verify that a raw :manpage:`syscall(2)` with the invalid system call
+ * number -1 fails with ENOSYS.
+ *
+ * The behavior of number -1 is architecture specific, so the test only runs on
+ * the architectures where it has been verified against the kernel entry code.
+ */
+
+#define _GNU_SOURCE
+#include <unistd.h>
+
+#include "tst_test.h"
+
+static void run(void)
+{
+	TST_EXP_FAIL2(syscall(-1), ENOSYS, "invalid syscall number -1");
+}
+
+static struct tst_test test = {
+	.test_all = run,
+	.supported_archs = (const char *const []) {
+		"x86_64",
+		"aarch64",
+		NULL
+	},
+};

---
base-commit: 7ca5dc366a558f3666223e6abe579edd90bafd38
change-id: 20260714-syscall_invalid_nr-cf61f64f2741

Best regards,
-- 
Andrea Cervesato <andrea.cervesato@suse.com>


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Re: [LTP] syscall02: test invalid syscall number -1

[linuxtestproject.agent]

Hi Andrea,

On Tue, 14 Jul 2026 12:56:04 +0200, Andrea Cervesato wrote:
> syscall02: test invalid syscall number -1

> Add a test verifying that a raw syscall() with the reserved number -1
> fails with ENOSYS.

The subject and the doc comment inside the test both say "invalid syscall
number -1", but the commit body says "reserved number -1". These terms
carry different meanings. "Reserved" implies deliberate kernel allocation
for a specific purpose, while "invalid" is the user-facing description
for an out-of-range syscall number. Could "reserved" be changed to
"invalid" here to match the subject and the test description block?

Verdict - Needs revision

---
Note:

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Re: [LTP] [PATCH v2] syscall02: test invalid syscall number -1

[Cyril Hrubis]

Hi!
> diff --git a/runtest/syscalls b/runtest/syscalls
> index a021c79da49d4157c33187caed2dd3f0483759e0..8a777e61da1af59ba694e0bc5b5d92bb1d63754a 100644
> --- a/runtest/syscalls
> +++ b/runtest/syscalls
> @@ -1678,6 +1678,7 @@ sync_file_range01 sync_file_range01
>  sync_file_range02 sync_file_range02
>  
>  syscall01 syscall01
> +syscall02 syscall02
>  
>  sysconf01 sysconf01
>  
> diff --git a/testcases/kernel/syscalls/syscall/.gitignore b/testcases/kernel/syscalls/syscall/.gitignore
> index 74a081e40cb564e874e0f81478d3d1a0e95b6df4..fed1d81079450a7442023447285cd112924f7a10 100644
> --- a/testcases/kernel/syscalls/syscall/.gitignore
> +++ b/testcases/kernel/syscalls/syscall/.gitignore
> @@ -1 +1,2 @@
>  /syscall01
> +/syscall02
> diff --git a/testcases/kernel/syscalls/syscall/syscall02.c b/testcases/kernel/syscalls/syscall/syscall02.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..2fefcb17c763813653a6644759c2a035bee2c604
> --- /dev/null
> +++ b/testcases/kernel/syscalls/syscall/syscall02.c
> @@ -0,0 +1,31 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2026 SUSE LLC Andrea Cervesato <andrea.cervesato@suse.com>
> + */
> +
> +/*\
> + * Verify that a raw :manpage:`syscall(2)` with the invalid system call
> + * number -1 fails with ENOSYS.
> + *
> + * The behavior of number -1 is architecture specific, so the test only runs on
> + * the architectures where it has been verified against the kernel entry code.
> + */
> +
> +#define _GNU_SOURCE
> +#include <unistd.h>
> +
> +#include "tst_test.h"
> +
> +static void run(void)
> +{
> +	TST_EXP_FAIL2(syscall(-1), ENOSYS, "invalid syscall number -1");
> +}
> +
> +static struct tst_test test = {
> +	.test_all = run,
> +	.supported_archs = (const char *const []) {
> +		"x86_64",
> +		"aarch64",
> +		NULL
> +	},
> +};

I do not think that there is an architecture that has a valid syscall
mapped to -1. I do not think that we need to restrict the architecture
here.

-- 
Cyril Hrubis
chrubis@suse.cz

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