[PATCH v5 2/3] selftests/lam: Skip test if LAM is disabled

[Maciej Wieczor-Retman]

Until LASS is merged into the kernel [1], LAM is left disabled in the
config file. Running the LAM selftest with disabled LAM only results in
unhelpful output.

Use one of LAM syscalls() to determine whether the kernel was compiled
with LAM support (CONFIG_ADDRESS_MASKING) or not. Skip running the tests
in the latter case.

[1] https://lore.kernel.org/all/20241028160917.1380714-1-alexander.shishkin@xxxxxxxxxxxxxxx/

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
---
Changelog v4:
- Add this patch to the series.

 tools/testing/selftests/x86/lam.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tools/testing/selftests/x86/lam.c b/tools/testing/selftests/x86/lam.c
index 93f2f762d6b5..4ec37a4be007 100644
--- a/tools/testing/selftests/x86/lam.c
+++ b/tools/testing/selftests/x86/lam.c
@@ -124,6 +124,14 @@ static inline int cpu_has_lam(void)
 	return (cpuinfo[0] & (1 << 26));
 }
 
+static inline int kernel_has_lam(void)
+{
+	unsigned long bits;
+
+	syscall(SYS_arch_prctl, ARCH_GET_MAX_TAG_BITS, &bits);
+	return !!bits;
+}
+
 static inline int cpu_has_la57(void)
 {
 	return !system("grep -wq la57 /proc/cpuinfo");
@@ -1181,6 +1189,11 @@ int main(int argc, char **argv)
 		return KSFT_SKIP;
 	}
 
+	if (!kernel_has_lam()) {
+		ksft_print_msg("LAM is disabled in the kernel!\n");
+		return KSFT_SKIP;
+	}
+
 	while ((c = getopt(argc, argv, "ht:")) != -1) {
 		switch (c) {
 		case 't':
-- 
2.47.1