The soname from the vDSO is not a public API. Furthermore it requires
libc to implement dlsym() and friends.

Use the facilities from parse_vdso.c instead which uses the official
vDSO ABI to find it, aligned with the other vDSO selftests.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20260227-vdso-selftest-cleanups-v2-5-d84830fa8beb@linutronix.de

This reverts commit c9fbaa879508 ("selftests: vDSO: parse_vdso: Use UAPI
headers instead of libc headers")

The kernel headers were used to make parse_vdso.c compatible with
nolibc.  Unfortunately linux/elf.h is incompatible with glibc's
sys/auxv.h. When using glibc it is therefore not possible build
parse_vdso.c as part of the same compilation unit as its caller
as sys/auxv.h is needed for getauxval().

In the meantime nolibc gained its own elf.h, providing compatibility
with the documented libc interfaces.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20260227-vdso-selftest-cleanups-v2-1-d84830fa8beb@linutronix.de

vdso_test_abi provides the exact same functionality, properly uses
kselftest.h and explicitly calls into the vDSO without relying on the libc.

Drop the pointless testcase.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250812-vdso-tests-fixes-v2-8-90f499dd35f8@linutronix.de

Functions definitions without any argument list produce a warning with
-Wstrict-prototypes:

vdso_test_correctness.c:111:13: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  111 | static void fill_function_pointers()
      |             ^~~~~~~~~~~~~~~~~~~~~~

Explicitly use an empty argument list.

Now that all selftests a free of this warning, enable it in the Makefile.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250611-selftests-vdso-fixes-v3-7-e62e37a6bcf5@linutronix.de

Protect against common programming errors through compiler warnings.
These warnings are also used for the kernel itself.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250611-selftests-vdso-fixes-v3-6-e62e37a6bcf5@linutronix.de

vdso_standalone_test_x86 provides its own ASM syscall wrappers and
_start() implementation. The in-tree nolibc library already provides
this functionality for multiple architectures. By making use of nolibc,
the standalone testcase can be built from the exact same codebase as the
non-standalone version.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/all/20250226-parse_vdso-nolibc-v2-16-28e14e031ed8@linutronix.de

To allow the usage of parse_vdso.c together with a limited libc like
nolibc, use the kernels own elf.h and auxvec.h headers.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/all/20250226-parse_vdso-nolibc-v2-12-28e14e031ed8@linutronix.de

Rather than building on supported archs, build on all archs, and then
use the presence of the symbol in the vDSO to either skip the test or
move forward with it.

Note that this means that this test no longer checks whether the symbol
was correctly added to the kernel. But hopefully this will be clear
enough to developers and we'll cross our fingers that symbols aren't
removed by accident and not caught after this change.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Rather than using symlinks to find the vgetrandom-chacha.S file for each
arch, store this in a file that uses the compiler to determine
architecture, and then make use of weak symbols to skip the test on
architectures that don't provide the code.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Provide the s390 specific vdso getrandom() architecture backend.

_vdso_rng_data required data is placed within the _vdso_data vvar page,
by using a hardcoded offset larger than vdso_data.

As required the chacha20 implementation does not write to the stack.

The implementation follows more or less the arm64 implementations and
makes use of vector instructions. It has a fallback to the getrandom()
system call for machines where the vector facility is not installed.

The check if the vector facility is installed, as well as an
optimization for machines with the vector-enhancements facility 2, is
implemented with alternatives, avoiding runtime checks.

Note that __kernel_getrandom() is implemented without the vdso user
wrapper which would setup a stack frame for odd cases (aka very old
glibc variants) where the caller has not done that. All callers of
__kernel_getrandom() are required to setup a stack frame, like the C ABI
requires it.

The vdso testcases vdso_test_getrandom and vdso_test_chacha pass.

Benchmark on a z16:

    $ ./vdso_test_getrandom bench-single
       vdso: 25000000 times in 0.493703559 seconds
    syscall: 25000000 times in 6.584025337 seconds

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>