selftests/x86: Add test_vdso to test getcpu()

I'll eventually add tests for more vDSO functions here.

Signed-off-by: Andy Lutomirski <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Brian Gerst <[e-mail]>
Cc: Denys Vlasenko <[e-mail]>
Cc: H. Peter Anvin <[e-mail]>
Cc: Josh Poimboeuf <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Megha <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

tools/testing/selftests/x86/Makefile

···
 
 TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall test_mremap_vdso \
 			check_initial_reg_state sigreturn ldt_gdt iopl \
-			protection_keys
+			protection_keys test_vdso
 TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \
 			vdso_restorer

tools/testing/selftests/x86/test_vdso.c

···
+/*
+ * ldt_gdt.c - Test cases for LDT and GDT access
+ * Copyright (c) 2011-2015 Andrew Lutomirski
+ */
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <sys/time.h>
+#include <time.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <dlfcn.h>
+#include <string.h>
+#include <errno.h>
+#include <sched.h>
+#include <stdbool.h>
+
+#ifndef SYS_getcpu
+# ifdef __x86_64__
+#  define SYS_getcpu 309
+# else
+#  define SYS_getcpu 318
+# endif
+#endif
+
+int nerrs = 0;
+
+#ifdef __x86_64__
+# define VSYS(x) (x)
+#else
+# define VSYS(x) 0
+#endif
+
+typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
+
+const getcpu_t vgetcpu = (getcpu_t)VSYS(0xffffffffff600800);
+getcpu_t vdso_getcpu;
+
+void fill_function_pointers()
+{
+	void *vdso = dlopen("linux-vdso.so.1",
+			    RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
+	if (!vdso)
+		vdso = dlopen("linux-gate.so.1",
+			      RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
+	if (!vdso) {
+		printf("[WARN]\tfailed to find vDSO\n");
+		return;
+	}
+
+	vdso_getcpu = (getcpu_t)dlsym(vdso, "__vdso_getcpu");
+	if (!vdso_getcpu)
+		printf("Warning: failed to find getcpu in vDSO\n");
+}
+
+static long sys_getcpu(unsigned * cpu, unsigned * node,
+		       void* cache)
+{
+	return syscall(__NR_getcpu, cpu, node, cache);
+}
+
+static void test_getcpu(void)
+{
+	printf("[RUN]\tTesting getcpu...\n");
+
+	for (int cpu = 0; ; cpu++) {
+		cpu_set_t cpuset;
+		CPU_ZERO(&cpuset);
+		CPU_SET(cpu, &cpuset);
+		if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
+			return;
+
+		unsigned cpu_sys, cpu_vdso, cpu_vsys,
+			node_sys, node_vdso, node_vsys;
+		long ret_sys, ret_vdso = 1, ret_vsys = 1;
+		unsigned node;
+
+		ret_sys = sys_getcpu(&cpu_sys, &node_sys, 0);
+		if (vdso_getcpu)
+			ret_vdso = vdso_getcpu(&cpu_vdso, &node_vdso, 0);
+		if (vgetcpu)
+			ret_vsys = vgetcpu(&cpu_vsys, &node_vsys, 0);
+
+		if (!ret_sys)
+			node = node_sys;
+		else if (!ret_vdso)
+			node = node_vdso;
+		else if (!ret_vsys)
+			node = node_vsys;
+
+		bool ok = true;
+		if (!ret_sys && (cpu_sys != cpu || node_sys != node))
+			ok = false;
+		if (!ret_vdso && (cpu_vdso != cpu || node_vdso != node))
+			ok = false;
+		if (!ret_vsys && (cpu_vsys != cpu || node_vsys != node))
+			ok = false;
+
+		printf("[%s]\tCPU %u:", ok ? "OK" : "FAIL", cpu);
+		if (!ret_sys)
+			printf(" syscall: cpu %u, node %u", cpu_sys, node_sys);
+		if (!ret_vdso)
+			printf(" vdso: cpu %u, node %u", cpu_vdso, node_vdso);
+		if (!ret_vsys)
+			printf(" vsyscall: cpu %u, node %u", cpu_vsys,
+			       node_vsys);
+		printf("\n");
+
+		if (!ok)
+			nerrs++;
+	}
+}
+
+int main(int argc, char **argv)
+{
+	fill_function_pointers();
+
+	test_getcpu();
+
+	return nerrs ? 1 : 0;
+}