configure: Autodetect TLS bug on ARM with old gcc and apply workaround
Check if compiler being used contains the bug. GCC 7.3.0 is the oldest
version containing the fix, and version 6.3.0 is known to contain the
bug. Bug is only known to appear so far only on ARM32. If the bug is
present, gcc will generate a wrong binary which wil lend up segfaulting
when accessing TLS (__thread) variables under certain conditions.
Related: OS#4062
Related: SYS#4628
Change-Id: I8acc2cf41b73da0c3290f1cefd79f2bc68b0e77d
diff --git a/m4/check_tls_gcc_arm_bug.m4 b/m4/check_tls_gcc_arm_bug.m4
new file mode 100644
index 0000000..73b3e95
--- /dev/null
+++ b/m4/check_tls_gcc_arm_bug.m4
@@ -0,0 +1,29 @@
+# OS#4062 (https://osmocom.org/issues/4062)
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81142
+# SYS#4628
+
+# Check if We need to apply workaround for TLS bug on ARM platform for GCC < 7.3.0.
+# TLS_GCC_ARM_BUG_CFLAGS is filled with required workaround bits if needed.
+
+AC_DEFUN([CHECK_TLS_GCC_ARM_BUG], [
+ TLS_GCC_ARM_BUG_CFLAGS=""
+ AC_MSG_CHECKING([whether to workaround TLS bug in old gcc on ARM platforms])
+ AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
+ [[
+ #define GCC_VERSION (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)
+ /* Check for ARM 32 bit and gcc smaller than 7.3.0 */
+ /* We need to explicitly exclude GNUC compatible compilers, since they also define GNUC related tokens */
+ #if __arm__ && \
+ !defined(__clang__) && !defined(__llvm__) && !defined(__INTEL_COMPILER) && \
+ defined(__GNUC__) && GCC_VERSION < 70300
+ #error TLS bug present!
+ #endif
+ ]])],
+ [tls_bug_present=no],
+ [tls_bug_present=yes])
+ AS_IF([test "x$tls_bug_present" = "xyes"],[
+ TLS_GCC_ARM_BUG_CFLAGS="-mtls-dialect=gnu2"
+ ])
+ AC_SUBST([TLS_GCC_ARM_BUG_CFLAGS])
+ AC_MSG_RESULT([$TLS_GCC_ARM_BUG_CFLAGS])
+])