Re: [PATCH v2 1/2] KVM: selftests: Make rseq compatible with glibc-2.35

----- On Aug 10, 2022, at 6:41 AM, Gavin Shan gshan@redhat.com wrote:

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

---

tools/testing/selftests/kvm/Makefile | 5 +++-- tools/testing/selftests/kvm/rseq_test.c | 28 +++++++------------------ 2 files changed, 11 insertions(+), 22 deletions(-)

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index c7f47429d6cd..89c9a8c52c5f 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -197,7 +197,8 @@ 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 "$$TMP", -no-pie) @@ -206,7 +207,7 @@ no-pie-option := $(call try-run, echo 'int main() { return 0; }' | \ pgste-option = $(call try-run, echo 'int main() { return 0; }' | \ $(CC) -Werror -Wl$(comma)--s390-pgste -x c - -o "$$TMP",-Wl$(comma)--s390-pgste)

+LDLIBS += -ldl LDFLAGS += -pthread $(no-pie-option) $(pgste-option)

# After inclusion, $(OUTPUT) is defined and diff --git a/tools/testing/selftests/kvm/rseq_test.c b/tools/testing/selftests/kvm/rseq_test.c index a54d4d05a058..2cd5fe49ac8b 100644 --- a/tools/testing/selftests/kvm/rseq_test.c +++ b/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

@@ -37,6 +29,7 @@ static __thread volatile struct rseq __rseq = { #define NR_TASK_MIGRATIONS 100000

static pthread_t migration_thread; +static struct rseq_abi *__rseq;

What is this ?

static cpu_set_t possible_mask; static int min_cpu, max_cpu; static bool done; @@ -49,14 +42,6 @@ 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 +203,10 @@ 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));
  

• __rseq = rseq_get_abi();

  /*

  • Create and run a dummy VM that immediately exits to userspace via

@@ -256,7 +244,7 @@ int main(int argc, char *argv[]) */ smp_rmb(); cpu = sched_getcpu();

• 	rseq_cpu = READ_ONCE(__rseq.cpu_id);
  

• 	rseq_cpu = READ_ONCE(__rseq->cpu_id);
  

#include <rseq.h>

and use

rseq_current_cpu_raw().

Thanks,

Mathieu

	smp_rmb();
} while (snapshot != atomic_read(&seq_cnt));

@@ -278,7 +266,7 @@ int main(int argc, char *argv[])

kvm_vm_free(vm);

• sys_rseq(RSEQ_FLAG_UNREGISTER);

• rseq_unregister_current_thread();

  return 0;

}

2.23.0