KVM: selftests: Make rseq compatible with glibc-2.35

The rseq information is registered by TLS, starting from glibc-2.35.
In this case, the test always fails due to syscall(__NR_rseq). For
example, on RHEL9.1 where upstream glibc-2.35 features are enabled
on downstream glibc-2.34, the test fails like below.

  # ./rseq_test
  ==== Test Assertion Failure ====
    rseq_test.c:60: !r
    pid=112043 tid=112043 errno=22 - Invalid argument
       1        0x0000000000401973: main at rseq_test.c:226
       2        0x0000ffff84b6c79b: ?? ??:0
       3        0x0000ffff84b6c86b: ?? ??:0
       4        0x0000000000401b6f: _start at ??:?
    rseq failed, errno = 22 (Invalid argument)
  # rpm -aq | grep glibc-2
  glibc-2.34-39.el9.aarch64

Fix the issue by using "../rseq/rseq.c" to fetch the rseq information,
registred by TLS if it exists. Otherwise, we're going to register our
own rseq information as before.
Reported-by: Yihuang Yu <yihyu@redhat.com>
Suggested-by: Florian Weimer <fweimer@redhat.com>
Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Message-Id: <20220810104114.6838-2-gshan@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/Makefile

@@ -199,7 +199,8 @@ endif
 CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \
 	-fno-stack-protector -fno-PIE -I$(LINUX_TOOL_INCLUDE) \
 	-I$(LINUX_TOOL_ARCH_INCLUDE) -I$(LINUX_HDR_PATH) -Iinclude \
-	-I$(<D) -Iinclude/$(UNAME_M) -I.. $(EXTRA_CFLAGS) $(KHDR_INCLUDES)
+	-I$(<D) -Iinclude/$(UNAME_M) -I ../rseq -I.. $(EXTRA_CFLAGS) \
+	$(KHDR_INCLUDES)
 
 no-pie-option := $(call try-run, echo 'int main() { return 0; }' | \
         $(CC) -Werror -no-pie -x c - -o "$$TMP", -no-pie)
@@ -208,7 +209,7 @@ no-pie-option := $(call try-run, echo 'int main() { return 0; }' | \
 pgste-option = $(call try-run, echo 'int main() { return 0; }' | \
 	$(CC) -Werror -Wl$(comma)--s390-pgste -x c - -o "$$TMP",-Wl$(comma)--s390-pgste)
 
-
+LDLIBS += -ldl
 LDFLAGS += -pthread $(no-pie-option) $(pgste-option)
 
 # After inclusion, $(OUTPUT) is defined and

tools/testing/selftests/kvm/rseq_test.c

@@ -20,15 +20,7 @@
 #include "processor.h"
 #include "test_util.h"
 
-static __thread volatile struct rseq __rseq = {
-	.cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
-};
-
-/*
- * Use an arbitrary, bogus signature for configuring rseq, this test does not
- * actually enter an rseq critical section.
- */
-#define RSEQ_SIG 0xdeadbeef
+#include "../rseq/rseq.c"
 
 /*
  * Any bug related to task migration is likely to be timing-dependent; perform
@@ -49,14 +41,6 @@ static void guest_code(void)
 		GUEST_SYNC(0);
 }
 
-static void sys_rseq(int flags)
-{
-	int r;
-
-	r = syscall(__NR_rseq, &__rseq, sizeof(__rseq), flags, RSEQ_SIG);
-	TEST_ASSERT(!r, "rseq failed, errno = %d (%s)", errno, strerror(errno));
-}
-
 static int next_cpu(int cpu)
 {
 	/*
@@ -218,7 +202,9 @@ int main(int argc, char *argv[])
 
 	calc_min_max_cpu();
 
-	sys_rseq(0);
+	r = rseq_register_current_thread();
+	TEST_ASSERT(!r, "rseq_register_current_thread failed, errno = %d (%s)",
+		    errno, strerror(errno));
 
 	/*
 	 * Create and run a dummy VM that immediately exits to userspace via
@@ -256,7 +242,7 @@ int main(int argc, char *argv[])
 			 */
 			smp_rmb();
 			cpu = sched_getcpu();
-			rseq_cpu = READ_ONCE(__rseq.cpu_id);
+			rseq_cpu = rseq_current_cpu_raw();
 			smp_rmb();
 		} while (snapshot != atomic_read(&seq_cnt));
 
@@ -278,7 +264,7 @@ int main(int argc, char *argv[])
 
 	kvm_vm_free(vm);
 
-	sys_rseq(RSEQ_FLAG_UNREGISTER);
+	rseq_unregister_current_thread();
 
 	return 0;
 }