Disable SFrame support by default

And add extra checks to enable for binutils 2.45 and if the architecture
explicitly enables it.  When SFrame is disabled, all the related code
is also not enabled for backtrace() and _dl_find_object(), so SFrame
backtracking is not used even if the binary has the SFrame segment.

This patch also adds some other related fixes:

  * Fixed an issue with AC_CHECK_PROG_VER, where the READELF_SFRAME
    usage prevented specifying a different readelf through READELF
    environment variable at configure time.

  * Add an extra arch-specific internal definition,
    libc_cv_support_sframe, to disable --enable-sframe on architectures
    that have binutils but not glibc support (s390x).

  * Renamed the tests without the .sframe segment and move the
    tst-backtrace1 from pthread to debug.

  * Use the built compiler strip to remove the .sframe segment,
    instead of the system one (which might not support SFrame).

Checked on x86_64-linux-gnu and aarch64-linux-gnu.

Reviewed-by: Sam James <sam@gentoo.org>

configure.ac

@@ -441,10 +441,10 @@ case "$enable_fortify_source" in
 esac
 
 AC_ARG_ENABLE([sframe],
-	      [AS_HELP_STRING([--disable-sframe],
-			     [Disable building with SFrame stack trace information @<:@default=yes if GNU as is 2.41 or older@:>@])],
+	      [AS_HELP_STRING([--enable-sframe],
+			      [Enable building with SFrame support @<:@default=no@:>@])],
 	      [use_sframe=$enableval],
-	      [use_sframe=notset])
+	      [use_sframe=no])
 
 # We keep the original values in `$config_*' and never modify them, so we
 # can write them unchanged into config.make.  Everything else uses
@@ -2121,16 +2121,24 @@ AC_SUBST(libc_cv_test_cc_mprefer_vector_width)
 AC_SUBST(test_enable_cet)
 AC_SUBST(libc_cv_test_x86_have_amx_tile)
 
-# Glibc stacktracer supports SFrame v2 or newer
-libc_cv_readelf_version_ok=yes
-# SFrame is supported from 2.41 or higher
-AC_CHECK_PROG_VER(READELF_SFRAME, $READELF, --version,
-  [GNU readelf.* \([0-9][0-9]*\.[0-9.]*\)],
-  [2.4[1-9]*|2.[5-9][0-9]*|[3-9].*|[1-9][0-9][0-9]*],
-  libc_cv_readelf_version_ok=no)
+enable_gsframe=no
+if test $use_sframe = yes; then
+  # SFrame requires to be explicit enabled by the architecture
+  if test -z $libc_cv_support_sframe; then
+    AC_MSG_FAILURE([the architecture doesn't support SFrame])
+  fi
 
-# Check the current toolchain for SFrame support
-if test $libc_cv_readelf_version_ok = yes; then
+  # SFrame requires binutils 2.45 or higher.
+  libc_cv_sframe_readelf_version=yes
+  AC_CHECK_PROG_VER(READELF, $READELF, --version,
+    [GNU readelf.* \([0-9][0-9]*\.[0-9.]*\)],
+    [2.4[5-9]*|2.[5-9][0-9]*|2.[1-9][0-9][0-9]*|[3-9]*|[1-9][0-9]*],
+    libc_cv_sframe_readelf_version=no)
+  if test $libc_cv_sframe_readelf_version == no; then
+    AC_MSG_FAILURE([binutils too old to enable SFrame])
+  fi
+
+  # Check if the current toolchain supports SFrame
   AC_CACHE_CHECK([for SFrame support], libc_cv_default_sframe,
   [dnl
 cat > conftest.c <<EOF
@@ -2139,25 +2147,23 @@ int test_function(void)
   return 42;
 }
 EOF
-  libc_cv_default_sframe=no
-  if ${CC} -c conftest.c -o conftest.o -Wa,--gsframe >/dev/null 2>&1 && \
-     # Check if .sframe section is present and if version > 1
-     $READELF --sframe conftest.o | grep "SFRAME_VER" | grep -qv "VERSION_1"; then
-          libc_cv_default_sframe=yes
-  fi
-  rm -f conftest.c conftest.o
+    libc_cv_default_sframe=no
+    if ${CC} -c conftest.c -o conftest.o -Wa,--gsframe >/dev/null 2>&1 && \
+       # Check if .sframe section is present and if version > 1
+       $READELF --sframe conftest.o | grep "SFRAME_VER" | grep -qv "VERSION_1"; then
+      libc_cv_default_sframe=yes
+    fi
+    rm -f conftest.c conftest.o
   ])
-fi
 
-# Prevent enabling sframe on non-supporting toolchains
-enable_gsframe=no
-if test $use_sframe$libc_cv_default_sframe = yesyes || \
-   test $use_sframe$libc_cv_default_sframe = notsetyes; then
+  if test $libc_cv_default_sframe == no; then
+    AC_MSG_FAILURE([toolchain doesn't support SFrame v2 or higher])
+  fi
+
   enable_gsframe=yes
-elif test $use_sframe = yes; then
-   AC_MSG_FAILURE([toolchain doesn't support SFrame v2 or higher])
+  AC_DEFINE(ENABLE_SFRAME)
 fi
-AC_SUBST(enable_gsframe)
+LIBC_CONFIG_VAR([enable-gsframe], [$enable_gsframe])
 
 # Set the `multidir' variable by grabbing the variable from the compiler.
 # We do it once and save the result in a generated makefile.