[PATCH 3/9] KVM: selftests: Add pthread_attr_setaffinity_np fallback

[Aqib Faruqui <aqibaf@amazon.com>]

The pthread_attr_setaffinity_np function is a GNU extension that may not
be available in non-glibc C libraries. Some KVM selftests use this
function for CPU affinity control.

Add a function declaration and weak stub implementation for non-glibc
builds. This allows tests to build, with the affinity setting being a
no-op and errno set for the caller when the actual function is not available.

Signed-off-by: Aqib Faruqui <aqibaf@amazon.com>
---
 tools/testing/selftests/kvm/include/kvm_util.h |  4 ++++
 tools/testing/selftests/kvm/lib/kvm_util.c     | 11 +++++++++++
 2 files changed, 15 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 7fae7f5e7..8177178b5 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -31,6 +31,10 @@
 #include "kvm_util_types.h"
 #include "sparsebit.h"
 
+#ifndef __GLIBC__
+int pthread_attr_setaffinity_np(pthread_attr_t *attr, size_t cpusetsize, const cpu_set_t *cpuset);
+#endif /* __GLIBC__ */
+
 #define KVM_DEV_PATH "/dev/kvm"
 #define KVM_MAX_VCPUS 512
 
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index c3f5142b0..5ce80303d 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -20,6 +20,17 @@
 
 #define KVM_UTIL_MIN_PFN	2
 
+#ifndef __GLIBC__
+int __attribute__((weak))
+pthread_attr_setaffinity_np(pthread_attr_t *__attr,
+				size_t __cpusetsize,
+				const cpu_set_t *__cpuset)
+{
+	errno = ENOSYS;
+	return -1;
+}
+#endif
+
 uint32_t guest_random_seed;
 struct guest_random_state guest_rng;
 static uint32_t last_guest_seed;
-- 
2.47.3