selftests: vDSO: fix the way vDSO functions are called for powerpc

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: c7e5789b24d3 ("kselftest: Move test_vdso to the vDSO test suite")
Fixes: 2e9a97256616 ("selftests: vdso: Add a selftest for vDSO getcpu()")
Fixes: 693f5ca08ca0 ("kselftest: Extend vDSO selftest")
Fixes: b2f1c3db2887 ("kselftest: Extend vdso correctness test to clock_gettime64")
Fixes: 4920a2590e91 ("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>

1 files changed, 3 insertions, 2 deletions

diff --git a/tools/testing/selftests/vDSO/vdso_test_getrandom.c b/tools/testing/selftests/vDSO/vdso_test_getrandom.c
index 5db8ac8999cd..351daeb649c8 100644
--- a/tools/testing/selftests/vDSO/vdso_test_getrandom.c
+++ b/tools/testing/selftests/vDSO/vdso_test_getrandom.c
@@ -22,6 +22,7 @@
 #include "../kselftest.h"
 #include "parse_vdso.h"
 #include "vdso_config.h"
+#include "vdso_call.h"
 
 #ifndef timespecsub
 #define	timespecsub(tsp, usp, vsp)					\
@@ -116,7 +117,7 @@ static void vgetrandom_init(void)
 		printf("%s is missing!\n", name);
 		exit(KSFT_FAIL);
 	}
-	ret = vgrnd.fn(NULL, 0, 0, &vgrnd.params, ~0UL);
+	ret = VDSO_CALL(vgrnd.fn, 5, NULL, 0, 0, &vgrnd.params, ~0UL);
 	if (ret == -ENOSYS) {
 		printf("unsupported architecture\n");
 		exit(KSFT_SKIP);
@@ -137,7 +138,7 @@ static ssize_t vgetrandom(void *buf, size_t len, unsigned long flags)
 			exit(KSFT_FAIL);
 		}
 	}
-	return vgrnd.fn(buf, len, flags, state, vgrnd.params.size_of_opaque_state);
+	return VDSO_CALL(vgrnd.fn, 5, buf, len, flags, state, vgrnd.params.size_of_opaque_state);
 }
 
 enum { TRIALS = 25000000, THREADS = 256 };