[PATCH] aarch64: Skip traditional GD/LD TLS which are unsupported by Clang and LLD [BZ #28205]

[Fangrui Song via Libc-alpha <libc-alpha@sourceware.org>]

TLSDESC is the default on aarch64.  Clang doesn't support
-mtls-dialect=trad.  Its integrated assembler doesn't support the
marker.  LLD's doesn't support R_AARCH64_TLSGD_*/R_AARCH64_TLSLD_*
relocations.  Just skip the tests.

With https://sourceware.org/pipermail/libc-alpha/2021-August/129904.html
("aarch64: Make elf_machine_{load_address, dynamic} robust [BZ #28203]"),
if we allow LLD in configure.ac,
`make check` test results of LLD are on par with GNU ld.
---
 config.h.in       |  3 +++
 configure         | 38 ++++++++++++++++++++++++++++++++++++++
 configure.ac      | 24 ++++++++++++++++++++++++
 elf/tst-tls1.c    |  7 +++++--
 elf/tst-tls2.c    |  6 ++++--
 elf/tst-tls3.c    |  8 ++++----
 elf/tst-tlsmod1.c |  6 ++++--
 elf/tst-tlsmod2.c |  4 +++-
 elf/tst-tlsmod3.c |  5 ++++-
 elf/tst-tlsmod4.c |  4 +++-
 10 files changed, 92 insertions(+), 13 deletions(-)

diff --git a/config.h.in b/config.h.in
index 8b45a3a61d..f65605d4bd 100644
--- a/config.h.in
+++ b/config.h.in
@@ -198,6 +198,9 @@
 /* Define if CC supports attribute retain.  */
 #undef HAVE_GNU_RETAIN
 
+/* Define if CC and LD support -mtls-dialect=trad.  */
+#undef HAVE_MTLS_DIALECT_TRAD
+
 /* Define if the linker defines __ehdr_start.  */
 #undef HAVE_EHDR_START
 
diff --git a/configure b/configure
index 050f1a29cf..13e2a7374d 100755
--- a/configure
+++ b/configure
@@ -622,6 +622,7 @@ LIBGD
 libc_cv_cc_loop_to_function
 libc_cv_cc_submachine
 libc_cv_cc_nofma
+libc_cv_mtls_dialect_trad
 libc_cv_mtls_dialect_gnu2
 fno_unit_at_a_time
 libc_cv_has_glob_dat
@@ -6336,6 +6337,43 @@ $as_echo "$libc_cv_mtls_dialect_gnu2" >&6; }
 config_vars="$config_vars
 have-mtls-dialect-gnu2 = $libc_cv_mtls_dialect_gnu2"
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for -mtls-dialect=trad" >&5
+$as_echo_n "checking for -mtls-dialect=trad... " >&6; }
+if ${libc_cv_mtls_dialect_trad+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat > conftest.c <<EOF
+extern __thread int i;
+void foo (void)
+{
+  i = 10;
+}
+EOF
+if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS
+			-fPIC -mtls-dialect=trad -shared -o conftest.so conftest.c
+			1>&5'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+then
+  libc_cv_mtls_dialect_trad=yes
+else
+  libc_cv_mtls_dialect_trad=no
+fi
+rm -f conftest*
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_mtls_dialect_trad" >&5
+$as_echo "$libc_cv_mtls_dialect_trad" >&6; }
+if test $libc_cv_mtls_dialect_trad = yes; then
+  $as_echo "#define HAVE_MTLS_DIALECT_TRAD 1" >>confdefs.h
+
+fi
+
+config_vars="$config_vars
+have-mtls-dialect-trad = $libc_cv_mtls_dialect_trad"
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether cc puts quotes around section names" >&5
 $as_echo_n "checking whether cc puts quotes around section names... " >&6; }
 if ${libc_cv_have_section_quotes+:} false; then :
diff --git a/configure.ac b/configure.ac
index 5632277f9c..c73e271cc8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1501,6 +1501,30 @@ rm -f conftest*])
 AC_SUBST(libc_cv_mtls_dialect_gnu2)
 LIBC_CONFIG_VAR([have-mtls-dialect-gnu2], [$libc_cv_mtls_dialect_gnu2])
 
+AC_CACHE_CHECK([for -mtls-dialect=trad], libc_cv_mtls_dialect_trad,
+[dnl
+cat > conftest.c <<EOF
+extern __thread int i;
+void foo (void)
+{
+  i = 10;
+}
+EOF
+if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS
+			-fPIC -mtls-dialect=trad -shared -o conftest.so conftest.c
+			1>&AS_MESSAGE_LOG_FD])
+then
+  libc_cv_mtls_dialect_trad=yes
+else
+  libc_cv_mtls_dialect_trad=no
+fi
+rm -f conftest*])
+if test $libc_cv_mtls_dialect_trad = yes; then
+  AC_DEFINE(HAVE_MTLS_DIALECT_TRAD)
+fi
+AC_SUBST(libc_cv_mtls_dialect_trad)
+LIBC_CONFIG_VAR([have-mtls-dialect-trad], [$libc_cv_mtls_dialect_trad])
+
 AC_CACHE_CHECK(whether cc puts quotes around section names,
 	       libc_cv_have_section_quotes,
 	       [cat > conftest.c <<EOF
diff --git a/elf/tst-tls1.c b/elf/tst-tls1.c
index c31da56ce9..bfd6f81a29 100644
--- a/elf/tst-tls1.c
+++ b/elf/tst-tls1.c
@@ -39,7 +39,8 @@ do_test (void)
       result = 1;
     }
 
-
+  /* Clang and LLD do not support traditional GD/LD TLS on aarch64. */
+#if !defined (__aarch64__) || defined (HAVE_MTLS_DIALECT_TRAD)
   /* Get variables using local dynamic model.  */
   fputs ("get sum of foo and bar (LD)", stdout);
   ap = TLS_LD (foo);
@@ -56,8 +57,9 @@ do_test (void)
       printf ("bar = %d\n", *bp);
       result = 1;
     }
+#endif
 
-
+#if !defined (__aarch64__) || defined (HAVE_MTLS_DIALECT_TRAD)
   /* Get variables using generic dynamic model.  */
   fputs ("get sum of foo and bar (GD)", stdout);
   ap = TLS_GD (foo);
@@ -74,6 +76,7 @@ do_test (void)
       printf ("bar = %d\n", *bp);
       result = 1;
     }
+#endif
 
   return result;
 }
diff --git a/elf/tst-tls2.c b/elf/tst-tls2.c
index 963b8d6c88..0b5615a0ba 100644
--- a/elf/tst-tls2.c
+++ b/elf/tst-tls2.c
@@ -39,7 +39,7 @@ do_test (void)
       result = 1;
     }
 
-
+#if !defined (__aarch64__) || defined (HAVE_MTLS_DIALECT_TRAD)
   /* Get variables using local dynamic model.  */
   fputs ("get sum of foo and bar (LD)", stdout);
   ap = TLS_LD (foo);
@@ -56,8 +56,9 @@ do_test (void)
       printf ("bar = %d\n", *bp);
       result = 1;
     }
+#endif
 
-
+#if !defined (__aarch64__) || defined (HAVE_MTLS_DIALECT_TRAD)
   /* Get variables using generic dynamic model.  */
   fputs ("get sum of foo and bar (GD)", stdout);
   ap = TLS_GD (foo);
@@ -74,6 +75,7 @@ do_test (void)
       printf ("bar = %d\n", *bp);
       result = 1;
     }
+#endif
 
   return result;
 }
diff --git a/elf/tst-tls3.c b/elf/tst-tls3.c
index 7e0abb4c58..4dd6377b24 100644
--- a/elf/tst-tls3.c
+++ b/elf/tst-tls3.c
@@ -17,8 +17,7 @@ static int
 do_test (void)
 {
   int result = 0;
-  int *ap, *bp, *cp;
-
+  int *ap, *bp;
 
   /* Set the variable using the local exec model.  */
   puts ("set baz to 3 (LE)");
@@ -33,7 +32,8 @@ do_test (void)
   bp = TLS_IE (bar);
   *bp = 2;
 
-
+#if !defined (__aarch64__) || defined (HAVE_MTLS_DIALECT_TRAD)
+  int *cp;
   /* Get variables using local dynamic model.  */
   fputs ("get sum of foo, bar (GD) and baz (LD)", stdout);
   ap = TLS_GD (foo);
@@ -56,7 +56,7 @@ do_test (void)
       printf ("baz = %d\n", *cp);
       result = 1;
     }
-
+#endif
 
   result |= in_dso ();
 
diff --git a/elf/tst-tlsmod1.c b/elf/tst-tlsmod1.c
index 8d9156791b..00fb26ace0 100644
--- a/elf/tst-tlsmod1.c
+++ b/elf/tst-tlsmod1.c
@@ -14,7 +14,7 @@ int
 in_dso (void)
 {
   int result = 0;
-  int *ap, *bp, *cp;
+  int *ap, *bp;
 
   /* Get variables using initial exec model.  */
   fputs ("get sum of foo and bar (IE)", stdout);
@@ -34,7 +34,8 @@ in_dso (void)
       result = 1;
     }
 
-
+#if !defined (__aarch64__) || defined (HAVE_MTLS_DIALECT_TRAD)
+  int *cp;
   /* Get variables using generic dynamic model.  */
   fputs ("get sum of foo and bar and baz (GD)", stdout);
   ap = TLS_GD (foo);
@@ -57,6 +58,7 @@ in_dso (void)
       printf ("baz = %d\n", *cp);
       result = 1;
     }
+#endif
 
   return result;
 }
diff --git a/elf/tst-tlsmod2.c b/elf/tst-tlsmod2.c
index 40eb1407f8..ead3e97b1d 100644
--- a/elf/tst-tlsmod2.c
+++ b/elf/tst-tlsmod2.c
@@ -9,9 +9,10 @@ COMMON_INT_DEF(foo);
 int
 in_dso (int n, int *caller_foop)
 {
-  int *foop;
   int result = 0;
 
+#if !defined (__aarch64__) || defined (HAVE_MTLS_DIALECT_TRAD)
+  int *foop;
   puts ("foo");			/* Make sure PLT is used before macros.  */
   asm ("" ::: "memory");
 
@@ -29,6 +30,7 @@ in_dso (int n, int *caller_foop)
     }
 
   *foop = 16;
+#endif
 
   return result;
 }
diff --git a/elf/tst-tlsmod3.c b/elf/tst-tlsmod3.c
index 6d186c47ee..4dfdfe19f7 100644
--- a/elf/tst-tlsmod3.c
+++ b/elf/tst-tlsmod3.c
@@ -12,8 +12,10 @@ COMMON_INT_DEF(comm_n);
 int
 in_dso2 (void)
 {
-  int *foop;
   int result = 0;
+
+#if !defined (__aarch64__) || defined (HAVE_MTLS_DIALECT_TRAD)
+  int *foop;
   static int n;
   int *np;
 
@@ -32,6 +34,7 @@ in_dso2 (void)
   result |= in_dso (*foop = 42 + n++, foop);
 
   *foop = 16;
+#endif
 
   return result;
 }
diff --git a/elf/tst-tlsmod4.c b/elf/tst-tlsmod4.c
index 86889aac7e..ca1afd4390 100644
--- a/elf/tst-tlsmod4.c
+++ b/elf/tst-tlsmod4.c
@@ -9,9 +9,10 @@ COMMON_INT_DEF(baz);
 int
 in_dso (int n, int *caller_bazp)
 {
-  int *bazp;
   int result = 0;
 
+#if !defined (__aarch64__) || defined (HAVE_MTLS_DIALECT_TRAD)
+  int *bazp;
   puts ("foo");			/* Make sure PLT is used before macros.  */
   asm ("" ::: "memory");
 
@@ -29,6 +30,7 @@ in_dso (int n, int *caller_bazp)
     }
 
   *bazp = 16;
+#endif
 
   return result;
 }
-- 
2.32.0.605.g8dce9f2422-goog