The _rval register variable is meant to be an output operand of the asm
statement but is instead used as input operand.
clang 20.1 notices this and triggers -Wuninitialized warnings:
tools/testing/selftests/timers/auxclock.c:154:10: error: variable '_rval' is uninitialized when used here [-Werror,-Wuninitialized]
154 | return VDSO_CALL(self->vdso_clock_gettime64, 2, clockid, ts);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tools/testing/selftests/timers/../vDSO/vdso_call.h:59:10: note: expanded from macro 'VDSO_CALL'
59 | : "r" (_rval) \
| ^~~~~
tools/testing/selftests/timers/auxclock.c:154:10: note: variable '_rval' is declared here
tools/testing/selftests/timers/../vDSO/vdso_call.h:47:2: note: expanded from macro 'VDSO_CALL'
47 | register long _rval asm ("r3"); \
| ^
It seems the list of input and output operands have been switched around.
However as the argument registers are not always initialized they can not
be marked as pure inputs as that would trigger -Wuninitialized warnings.
Adding _rval as another input and output operand does also not work as it
would collide with the existing _r3 variable.
Instead reuse _r3 for both the argument and the return value.
Fixes: 6eda706a53 ("selftests: vDSO: fix the way vDSO functions are called for powerpc")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/all/20250812-vdso-tests-fixes-v2-1-90f499dd35f8@linutronix.de
Closes: https://lore.kernel.org/oe-kbuild-all/202506180223.BOOk5jDK-lkp@intel.com/
vdso_test_correctness test fails on powerpc:
~ # ./vdso_test_correctness
...
[RUN] Testing clock_gettime for clock CLOCK_REALTIME_ALARM (8)...
[FAIL] No such clock, but __vdso_clock_gettime returned 22
[RUN] Testing clock_gettime for clock CLOCK_BOOTTIME_ALARM (9)...
[FAIL] No such clock, but __vdso_clock_gettime returned 22
[RUN] Testing clock_gettime for clock CLOCK_SGI_CYCLE (10)...
[FAIL] No such clock, but __vdso_clock_gettime returned 22
...
[RUN] Testing clock_gettime for clock invalid (-1)...
[FAIL] No such clock, but __vdso_clock_gettime returned 22
[RUN] Testing clock_gettime for clock invalid (-2147483648)...
[FAIL] No such clock, but __vdso_clock_gettime returned 22
[RUN] Testing clock_gettime for clock invalid (2147483647)...
[FAIL] No such clock, but __vdso_clock_gettime returned 22
On powerpc, a call to a VDSO function is not an ordinary C function
call. Unlike several architectures which returns a negative error code
in case of an error, powerpc sets CR[SO] and returns the error code
as a positive value.
Define and use a macro called VDSO_CALL() which takes a pointer
to the function to call, the number of arguments and the arguments.
Also update ABI vdso documentation to reflect this subtlety.
Provide a specific version of VDSO_CALL() for powerpc that negates
the error code on return when CR[SO] is set.
Fixes: c7e5789b24 ("kselftest: Move test_vdso to the vDSO test suite")
Fixes: 2e9a972566 ("selftests: vdso: Add a selftest for vDSO getcpu()")
Fixes: 693f5ca08c ("kselftest: Extend vDSO selftest")
Fixes: b2f1c3db28 ("kselftest: Extend vdso correctness test to clock_gettime64")
Fixes: 4920a2590e ("selftests/vDSO: add tests for vgetrandom")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
