[DFSan] Add custom wrapper for _dl_get_tls_static_info.

Implementation is here:
https://code.woboq.org/userspace/glibc/elf/dl-tls.c.html#307

We use weak symbols to avoid linking issues with glibcs older than 2.27.

Reviewed By: stephan.yichao.zhao

Differential Revision: https://reviews.llvm.org/D93053

compiler-rt/lib/dfsan/dfsan_custom.cpp

@@ -461,6 +461,20 @@ SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_dl_iterate_phdr(
   return dl_iterate_phdr(dl_iterate_phdr_cb, &dipi);
 }
 
+// This function is only available for glibc 2.27 or newer.  Mark it weak so
+// linking succeeds with older glibcs.
+SANITIZER_WEAK_ATTRIBUTE void _dl_get_tls_static_info(size_t *sizep,
+                                                      size_t *alignp);
+
+SANITIZER_INTERFACE_ATTRIBUTE void __dfsw__dl_get_tls_static_info(
+    size_t *sizep, size_t *alignp, dfsan_label sizep_label,
+    dfsan_label alignp_label) {
+  assert(_dl_get_tls_static_info);
+  _dl_get_tls_static_info(sizep, alignp);
+  dfsan_set_label(0, sizep, sizeof(*sizep));
+  dfsan_set_label(0, alignp, sizeof(*alignp));
+}
+
 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfsw_ctime_r(const time_t *timep, char *buf, dfsan_label timep_label,
                      dfsan_label buf_label, dfsan_label *ret_label) {

compiler-rt/lib/dfsan/done_abilist.txt

@@ -183,6 +183,7 @@ fun:uselocale=discard
 
 # Functions that produce output does not depend on the input (need to zero the
 # shadow manually).
+fun:_dl_get_tls_static_info=custom
 fun:calloc=custom
 fun:clock_gettime=custom
 fun:dlopen=custom

compiler-rt/test/dfsan/custom.cpp

@@ -809,6 +809,22 @@ void test_dl_iterate_phdr() {
   dl_iterate_phdr(dl_iterate_phdr_test_cb, (void *)3);
 }
 
+// On glibc < 2.27, this symbol is not available.  Mark it weak so we can skip
+// testing in this case.
+__attribute__((weak)) extern "C" void _dl_get_tls_static_info(size_t *sizep,
+                                                              size_t *alignp);
+
+void test__dl_get_tls_static_info() {
+  if (!_dl_get_tls_static_info)
+    return;
+  size_t sizep = 0, alignp = 0;
+  dfsan_set_label(i_label, &sizep, sizeof(sizep));
+  dfsan_set_label(i_label, &alignp, sizeof(alignp));
+  _dl_get_tls_static_info(&sizep, &alignp);
+  ASSERT_ZERO_LABEL(sizep);
+  ASSERT_ZERO_LABEL(alignp);
+}
+
 void test_strrchr() {
   char str1[] = "str1str1";
   dfsan_set_label(i_label, &str1[7], 1);
@@ -1147,6 +1163,7 @@ int main(void) {
   assert(i_j_label != j_label);
   assert(i_j_label != k_label);
 
+  test__dl_get_tls_static_info();
   test_bcmp();
   test_calloc();
   test_clock_gettime();