Re: [PATCH v2 1/1] rseq/selftests: add __rseq_abi misalignment check

On Mon, Aug 06, 2018 at 03:27:23PM +0200, Vasily Gorbik wrote:

The kernel rseq syscall expects that struct rseq is 32 bytes aligned and returns EINVAL otherwise. Even though __rseq_abi is declared as static and proper aligned attribute is present __rseq_abi is a part of thread local storage. It turns out that on some platforms TLS itself is not properly aligned (at least for threads created), which is a glibc nptl bug and should be eventually fixed and backported. But in a meanwhile add __rseq_abi misalignment check, which would detect this situation and skip rseq test with some user friendly message.

glibc bug: https://sourceware.org/bugzilla/show_bug.cgi?id=23403

Signed-off-by: Vasily Gorbik gor@linux.ibm.com

Acked-by: Paul E. McKenney paulmck@linux.vnet.ibm.com

---

tools/testing/selftests/rseq/rseq.c | 20 +++++++++++++++++++ .../testing/selftests/rseq/run_param_test.sh | 4 ++-- 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c index 4847e97ed049..3de7f0e7442e 100644 --- a/tools/testing/selftests/rseq/rseq.c +++ b/tools/testing/selftests/rseq/rseq.c @@ -64,6 +64,24 @@ static int sys_rseq(volatile struct rseq *rseq_abi, uint32_t rseq_len, return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig); }

+/*

• • rseq syscall might fail on some platforms due to wrong alignment of TLS
• • variables:
• • https://sourceware.org/bugzilla/show_bug.cgi?id=23403
• • check if glibc bug is present and skip the test in this case
• */

+static void assert_rseq_abi_aligned(void) +{

• if ((unsigned long)&__rseq_abi & (__alignof__(__rseq_abi) - 1)) {

• fputs("__rseq_abi is not properly aligned, which is a known\n"
  

•       "glibc nptl bug (https://sourceware.org/bugzilla/show_bug.cgi?id=23403).\n"
  

•       "You need a fixed version of glibc to run this test.\n",
  

•       stderr);
  

• exit(4); /* skip this test */
  

• }

+}

int rseq_register_current_thread(void) { int rc, ret = 0; @@ -72,6 +90,7 @@ int rseq_register_current_thread(void) signal_off_save(&oldset); if (refcount++) goto end;

• assert_rseq_abi_aligned(); rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), 0, RSEQ_SIG); if (!rc) { assert(rseq_current_cpu_raw() >= 0);

@@ -94,6 +113,7 @@ int rseq_unregister_current_thread(void) signal_off_save(&oldset); if (--refcount) goto end;

• assert_rseq_abi_aligned(); rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), RSEQ_FLAG_UNREGISTER, RSEQ_SIG); if (!rc)

diff --git a/tools/testing/selftests/rseq/run_param_test.sh b/tools/testing/selftests/rseq/run_param_test.sh index 3acd6d75ff9f..56caf5e3de3e 100755 --- a/tools/testing/selftests/rseq/run_param_test.sh +++ b/tools/testing/selftests/rseq/run_param_test.sh @@ -34,9 +34,9 @@ function do_tests() local i=0 while [ "$i" -lt "${#TEST_LIST[@]}" ]; do echo "Running test ${TEST_NAME[$i]}"

• ./param_test ${TEST_LIST[$i]} -r ${REPS} ${@} ${EXTRA_ARGS} || exit 1
  

• ./param_test ${TEST_LIST[$i]} -r ${REPS} ${@} ${EXTRA_ARGS} || exit $?
  

  echo "Running compare-twice test ${TEST_NAME[$i]}"

• ./param_test_compare_twice ${TEST_LIST[$i]} -r ${REPS} ${@} ${EXTRA_ARGS} || exit 1
  

• ./param_test_compare_twice ${TEST_LIST[$i]} -r ${REPS} ${@} ${EXTRA_ARGS} || exit $?
  

  let "i++" done

}

2.18.0.13.gd42ae10

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