nptl: Move the rseq area to the 'extra TLS' block

Move the rseq area to the newly added 'extra TLS' block, this is the
last step in adding support for the rseq extended ABI. The size of the
rseq area is now dynamic and depends on the rseq features reported by
the kernel through the elf auxiliary vector. This will allow
applications to use rseq features past the 32 bytes of the original rseq
ABI as they become available in future kernels.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>

1 files changed, 67 insertions, 10 deletions

diff --git a/sysdeps/unix/sysv/linux/tst-rseq-disable.c b/sysdeps/unix/sysv/linux/tst-rseq-disable.c
index 0e191ff..8e9c11f 100644
--- a/sysdeps/unix/sysv/linux/tst-rseq-disable.c
+++ b/sysdeps/unix/sysv/linux/tst-rseq-disable.c
@@ -26,32 +26,82 @@
 #include <unistd.h>
 
 #ifdef RSEQ_SIG
+# include <sys/auxv.h>
+# include <dl-tls.h>
+# include "tst-rseq.h"
+
+/* Used to test private registration with the rseq system call because glibc
+   rseq is disabled.  */
+static __thread struct rseq local_rseq = {
+  .cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED,
+};
+
+/* Used to check if the address of the rseq area comes before or after the tls
+   blocks depending on the TLS model.  */
+static __thread char tls_var __attribute__ ((tls_model ("initial-exec")));
 
 /* Check that rseq can be registered and has not been taken by glibc.  */
 static void
 check_rseq_disabled (void)
 {
-  struct pthread *pd = THREAD_SELF;
+  struct rseq *rseq_abi = (struct rseq *) ((char *) __thread_pointer () +
+		           __rseq_offset);
+
+#if TLS_TCB_AT_TP
+  /* The rseq area block should come before the thread pointer and be at least
+     32 bytes. */
+  TEST_VERIFY (__rseq_offset <= -RSEQ_AREA_SIZE_INITIAL);
+
+  /* The rseq area block should come before TLS variables.  */
+  TEST_VERIFY ((intptr_t) rseq_abi < (intptr_t) &tls_var);
+#elif TLS_DTV_AT_TP
+  /* The rseq area block should come after the TCB, add the TLS block offset to
+     the rseq offset to get a value relative to the TCB and test that it's
+     non-negative.  */
+  TEST_VERIFY (__rseq_offset + TLS_TP_OFFSET >= 0);
+
+  /* The rseq area block should come after TLS variables.  */
+  TEST_VERIFY ((intptr_t) rseq_abi > (intptr_t) &tls_var);
+#else
+# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
+#endif
 
+  /* __rseq_flags is unused and should always be '0'.  */
   TEST_COMPARE (__rseq_flags, 0);
-  TEST_VERIFY ((char *) __thread_pointer () + __rseq_offset
-               == (char *) &pd->rseq_area);
+
+  /* When rseq is not registered, __rseq_size should always be '0'.  */
   TEST_COMPARE (__rseq_size, 0);
-  TEST_COMPARE ((int) pd->rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
 
-  int ret = syscall (__NR_rseq, &pd->rseq_area, sizeof (pd->rseq_area),
-                     0, RSEQ_SIG);
+  /* When rseq is not registered, the 'cpu_id' field should be set to
+     RSEQ_CPU_ID_REGISTRATION_FAILED.  */
+  TEST_COMPARE ((int) rseq_abi->cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
+
+  /* Test a rseq registration which should succeed since the internal
+     registration is disabled.  */
+  int ret = syscall (__NR_rseq, &local_rseq, RSEQ_AREA_SIZE_INITIAL, 0, RSEQ_SIG);
   if (ret == 0)
     {
-      ret = syscall (__NR_rseq, &pd->rseq_area, sizeof (pd->rseq_area),
+      /* A successful registration should set the cpu id.  */
+      TEST_VERIFY (local_rseq.cpu_id >= 0);
+
+      /* Test we can also unregister rseq.  */
+      ret = syscall (__NR_rseq, &local_rseq, RSEQ_AREA_SIZE_INITIAL,
                      RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
       TEST_COMPARE (ret, 0);
-      pd->rseq_area.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
     }
   else
     {
-      TEST_VERIFY (errno != -EINVAL);
-      TEST_VERIFY (errno != -EBUSY);
+      /* Check if we failed with EINVAL which would mean an invalid rseq flags,
+         a mis-aligned rseq area address or an incorrect rseq size.  */
+      TEST_VERIFY (errno != EINVAL);
+
+      /* Check if we failed with EBUSY which means an existing rseq
+         registration. */
+      TEST_VERIFY (errno != EBUSY);
+
+      /* Check if we failed with EFAULT which means an invalid rseq area
+         address.  */
+      TEST_VERIFY (errno != EFAULT);
     }
 }
 
@@ -71,6 +121,13 @@ proc_func (void *ignored)
 static int
 do_test (void)
 {
+  printf ("info: __rseq_size: %u\n", __rseq_size);
+  printf ("info: __rseq_offset: %td\n", __rseq_offset);
+  printf ("info: __rseq_flags: %u\n", __rseq_flags);
+  printf ("info: getauxval (AT_RSEQ_FEATURE_SIZE): %ld\n",
+          getauxval (AT_RSEQ_FEATURE_SIZE));
+  printf ("info: getauxval (AT_RSEQ_ALIGN): %ld\n", getauxval (AT_RSEQ_ALIGN));
+
   puts ("info: checking main thread");
   check_rseq_disabled ();