[LTP] [PATCH] syscall02: add invalid syscall number test

[Wei Gao]

On Mon, Jun 29, 2026 at 04:03:09PM +0200, Andrea Cervesato wrote:
> From: Andrea Cervesato <andrea.cervesato@suse.com>
> 
> Add a test verifying that syscall() returns ENOSYS when called with
> unimplemented syscall numbers. The chosen numbers stay above the syscall
> table and below the architecture-specific private ranges, so they are
> reliably invalid on every supported architecture.
> 
> Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
> ---
>  runtest/syscalls                              |  1 +
>  testcases/kernel/syscalls/syscall/.gitignore  |  1 +
>  testcases/kernel/syscalls/syscall/syscall02.c | 47 +++++++++++++++++++++++++++
>  3 files changed, 49 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..3bd9fa8cdcca257e03b358749ee7a2b676d8720d
> --- /dev/null
> +++ b/testcases/kernel/syscalls/syscall/syscall02.c
> @@ -0,0 +1,47 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2026 Andrea Cervesato <andrea.cervesato@suse.com>
> + */
> +
> +/*\
> + * Verify that :manpage:`syscall(2)` fails with ENOSYS when invoked with
> + * invalid syscall numbers.
> + *
> + * The syscall number is dispatched as an unsigned value on Linux. A value is
> + * reliably unimplemented on every supported architecture when it is:
> + *
> + * - above the syscall table
> + * - below the architecture-specific private syscall ranges (e.g. ARM's
> + *   0x0f0000 base)
> + * - without the x32 ABI bit (0x40000000) set
> + *
> + * Such a number is routed to sys_ni_syscall and returns ENOSYS.
> + */
> +
> +#include <unistd.h>
> +#include <sys/syscall.h>
> +
> +#include "tst_test.h"
> +
> +#define TC(x) {.scno = (long)(x), .desc = #x}
> +
> +static struct tcase {
> +	long scno;
> +	const char *desc;
> +} tcases[] = {
> +	TC(0x8000),
> +	TC(0xf000),
> +	TC(0xfffe),
> +};

I suggest add two more cases check:
1) -1
2) __NR_syscalls +1 (Base arch/powerpc/kernel/syscall.c)

> +
> +static void verify_syscall(unsigned int n)
> +{
> +	struct tcase *tc = &tcases[n];
> +
> +	TST_EXP_FAIL2(syscall(tc->scno), ENOSYS, "syscall(%s)", tc->desc);
> +}
> +
> +static struct tst_test test = {
> +	.test = verify_syscall,
> +	.tcnt = ARRAY_SIZE(tcases),
> +};
> 
> ---
> base-commit: ad68429b9cfd55b233733e45e600ffafa1458ac5
> change-id: 20260629-invalid_syscalls-0476c52d7d0c
> 
> Best regards,
> -- 
> Andrea Cervesato <andrea.cervesato@suse.com>
> 
> 
> -- 
> Mailing list info: https://lists.linux.it/listinfo/ltp