[RFC PATCH v2 05/11] selftests/rseq: Implement rseq numa node id field selftest

@@ -22,6 +22,8 @@ void test_cpu_pointer(void)
 	CPU_ZERO(&test_affinity);
 	for (i = 0; i < CPU_SETSIZE; i++) {
 		if (CPU_ISSET(i, &affinity)) {
+			int node;
+
 			CPU_SET(i, &test_affinity);
 			sched_setaffinity(0, sizeof(test_affinity),
 					&test_affinity);

@@ -29,6 +31,9 @@ void test_cpu_pointer(void)
 			assert(rseq_current_cpu() == i);
 			assert(rseq_current_cpu_raw() == i);
 			assert(rseq_cpu_start() == i);
+			node = rseq_fallback_current_node();
+			assert(rseq_current_node() == node);
+			assert(rseq_current_node_raw() == node);
 			CPU_CLR(i, &test_affinity);
 		}
 	}

@@ -147,6 +147,14 @@ struct rseq_abi {
 	 */
 	__u32 flags;
 
+	/*
+	 * Restartable sequences node_id field. Updated by the kernel. Read by
+	 * user-space with single-copy atomicity semantics. This field should
+	 * only be read by the thread which registered this data structure.
+	 * Aligned on 32-bit. Contains the current NUMA node ID.
+	 */
+	__u32 node_id;
+
 	/*
 	 * Flexible array member at end of structure, after last feature field.
 	 */

@@ -79,6 +79,11 @@ static int sys_rseq(struct rseq_abi *rseq_abi, uint32_t rseq_len,
 	return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig);
 }
 
+static int sys_getcpu(unsigned int *cpu, unsigned int *node)
+{
+	return syscall(__NR_getcpu, cpu, node, NULL);
+}
+
 int rseq_available(void)
 {
 	int rc;

@@ -199,3 +204,16 @@ int32_t rseq_fallback_current_cpu(void)
 	}
 	return cpu;
 }
+
+int32_t rseq_fallback_current_node(void)
+{
+	uint32_t cpu_id, node_id;
+	int ret;
+
+	ret = sys_getcpu(&cpu_id, &node_id);
+	if (ret) {
+		perror("sys_getcpu()");
+		return ret;
+	}
+	return (int32_t) node_id;
+}

@@ -20,6 +20,15 @@
 #include "rseq-abi.h"
 #include "compiler.h"
 
+#ifndef rseq_sizeof_field
+#define rseq_sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
+#endif
+
+#ifndef rseq_offsetofend
+#define rseq_offsetofend(TYPE, MEMBER) \
+	(offsetof(TYPE, MEMBER)	+ rseq_sizeof_field(TYPE, MEMBER))
+#endif
+
 /*
  * Empty code injection macros, override when testing.
  * It is important to consider that the ASM injection macros need to be

@@ -123,6 +132,11 @@ int rseq_unregister_current_thread(void);
  */
 int32_t rseq_fallback_current_cpu(void);
 
+/*
+ * Restartable sequence fallback for reading the current node number.
+ */
+int32_t rseq_fallback_current_node(void);
+
 /*
  * Values returned can be either the current CPU number, -1 (rseq is
  * uninitialized), or -2 (rseq initialization has failed).

@@ -132,6 +146,15 @@ static inline int32_t rseq_current_cpu_raw(void)
 	return RSEQ_ACCESS_ONCE(rseq_get_abi()->cpu_id);
 }
 
+/*
+ * Current NUMA node number.
+ */
+static inline uint32_t rseq_current_node_raw(void)
+{
+	assert((int) rseq_feature_size >= rseq_offsetofend(struct rseq_abi, node_id));
+	return RSEQ_ACCESS_ONCE(rseq_get_abi()->node_id);
+}
+
 /*
  * Returns a possible CPU number, which is typically the current CPU.
  * The returned CPU number can be used to prepare for an rseq critical

@@ -158,6 +181,14 @@ static inline uint32_t rseq_current_cpu(void)
 	return cpu;
 }
 
+static inline uint32_t rseq_current_node(void)
+{
+	if (rseq_likely((int) rseq_feature_size >= rseq_offsetofend(struct rseq_abi, node_id)))
+		return rseq_current_node_raw();
+	else
+		return rseq_fallback_current_node();
+}
+
 static inline void rseq_clear_rseq_cs(void)
 {
 	RSEQ_WRITE_ONCE(rseq_get_abi()->rseq_cs.arch.ptr, 0);