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>

INSTALL

@@ -291,10 +291,11 @@ passed to 'configure'.  For example:
 
      Default is to disable fortification.
 
-'--disable-sframe'
-     By default, the GNU C Library is built with '-Wa,--gsframe' if the
-     current GNU 'binutils' supports it.  You may want to use this
-     option if you don't plan to use SFrame stack tracer.
+'--enable-sframe'
+     Experimental option supported by some architectures, where
+     the GNU C Library is built with '-Wa,--gsframe' if the binutils
+     supports it.  This option also enables SFrame support for
+     backtrace.
 
    To build the library and related programs, type 'make'.  This will
 produce a lot of output, some of which may look like errors from 'make'

NEWS

@@ -31,9 +31,10 @@ Major new features:
   glibc.malloc.tcache_max to a larger value (max 4194304).
   Tcache is also significantly faster for small sizes.
 
-* New stack tracer using SFrame.  Introducing --disable-sframe a new
-  configuration flag.  Building glibc using sframe is automatically
-  enabled when the build system supports it.
+* A new configure option, "--eanble-sframe", can be used to enable
+  the SFrame support on the GNU C Libraries.  The SFrame is a new
+  stack trace information which can be used by backtrace.  It requires
+  binutils with minimum version of 2.45.
 
 Deprecated and removed features, and other changes affecting compatibility:
 

aclocal.m4

@@ -145,6 +145,10 @@ if test -z "$NM"; then
     NM=`$CC -print-prog-name=nm`
 fi
 AC_SUBST(NM)
+if test -z "$STRIP"; then
+    STRIP=`$CC -print-prog-name=strip`
+fi
+AC_SUBST(STRIP)
 ])
 
 dnl Run a static link test with -nostdlib -nostartfiles.

config.h.in

@@ -287,6 +287,9 @@
 /* Define if static PIE is enabled.  */
 #define ENABLE_STATIC_PIE 0
 
+/* Define if SFrame v2 is enabled.  */
+#define ENABLE_SFRAME 0
+
 /* The default value of x86 CET control.  */
 #define DEFAULT_DL_X86_CET_CONTROL cet_elf_property
 

config.make.in

@@ -51,7 +51,6 @@ c++-cstdlib-header = @CXX_CSTDLIB_HEADER@
 c++-cmath-header = @CXX_CMATH_HEADER@
 c++-bits-std_abs-h = @CXX_BITS_STD_ABS_H@
 enable-werror = @enable_werror@
-enable-gsframe = @enable_gsframe@
 
 have-z-execstack = @libc_cv_z_execstack@
 have-no-error-execstack = @libc_cv_no_error_execstack@
@@ -114,6 +113,7 @@ OBJDUMP = @OBJDUMP@
 OBJCOPY = @OBJCOPY@
 GPROF = @GPROF@
 READELF = @READELF@
+STRIP = @STRIP@
 
 # Installation tools.
 INSTALL = @INSTALL@

configure

@@ -620,8 +620,6 @@ DEFINES
 static_nss
 profile
 libc_cv_multidir
-enable_gsframe
-READELF_SFRAME
 libc_cv_test_x86_have_amx_tile
 test_enable_cet
 libc_cv_test_cc_mprefer_vector_width
@@ -694,6 +692,7 @@ MAKEINFO
 MSGFMT
 MAKE
 LD
+STRIP
 NM
 OBJDUMP
 READELF
@@ -1510,8 +1509,7 @@ Optional Features:
                           Use -D_FORTIFY_SOURCE=[1|2|3] to control code
                           hardening, defaults to highest possible value
                           supported by the build compiler.
-  --disable-sframe        Disable building with SFrame stack trace information
-                          [default=yes if GNU as is 2.41 or older]
+  --enable-sframe         Enable building with SFrame support [default=no]
 
 Optional Packages:
   --with-PACKAGE[=ARG]    use PACKAGE [ARG=yes]
@@ -4895,7 +4893,7 @@ if test ${enable_sframe+y}
 then :
   enableval=$enable_sframe; use_sframe=$enableval
 else case e in #(
-  e) use_sframe=notset ;;
+  e) use_sframe=no ;;
 esac
 fi
 
@@ -5142,6 +5140,10 @@ if test -z "$NM"; then
     NM=`$CC -print-prog-name=nm`
 fi
 
+if test -z "$STRIP"; then
+    STRIP=`$CC -print-prog-name=strip`
+fi
+
 
 
 # Accept binutils 2.39 or newer.
@@ -9356,21 +9358,30 @@ have-libgcc_s = $libc_cv_have_libgcc_s"
 
 
 
-# Glibc stacktracer supports SFrame v2 or newer
-libc_cv_readelf_version_ok=yes
-# SFrame is supported from 2.41 or higher
-for ac_prog in $READELF
+enable_gsframe=no
+if test $use_sframe = yes; then
+  # SFrame requires to be explicit enabled by the architecture
+  if test -z $libc_cv_support_sframe; then
+    { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: in '$ac_pwd':" >&5
+printf "%s\n" "$as_me: error: in '$ac_pwd':" >&2;}
+as_fn_error $? "the architecture doesn't support SFrame
+See 'config.log' for more details" "$LINENO" 5; }
+  fi
+
+  # SFrame requires binutils 2.45 or higher.
+  libc_cv_sframe_readelf_version=yes
+  for ac_prog in $READELF
 do
   # Extract the first word of "$ac_prog", so it can be a program name with args.
 set dummy $ac_prog; ac_word=$2
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
 printf %s "checking for $ac_word... " >&6; }
-if test ${ac_cv_prog_READELF_SFRAME+y}
+if test ${ac_cv_prog_READELF+y}
 then :
   printf %s "(cached) " >&6
 else case e in #(
-  e) if test -n "$READELF_SFRAME"; then
-  ac_cv_prog_READELF_SFRAME="$READELF_SFRAME" # Let the user override the test.
+  e) if test -n "$READELF"; then
+  ac_cv_prog_READELF="$READELF" # Let the user override the test.
 else
 as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH
@@ -9383,7 +9394,7 @@ do
   esac
     for ac_exec_ext in '' $ac_executable_extensions; do
   if as_fn_executable_p "$as_dir$ac_word$ac_exec_ext"; then
-    ac_cv_prog_READELF_SFRAME="$ac_prog"
+    ac_cv_prog_READELF="$ac_prog"
     printf "%s\n" "$as_me:${as_lineno-$LINENO}: found $as_dir$ac_word$ac_exec_ext" >&5
     break 2
   fi
@@ -9394,29 +9405,29 @@ IFS=$as_save_IFS
 fi ;;
 esac
 fi
-READELF_SFRAME=$ac_cv_prog_READELF_SFRAME
-if test -n "$READELF_SFRAME"; then
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $READELF_SFRAME" >&5
-printf "%s\n" "$READELF_SFRAME" >&6; }
+READELF=$ac_cv_prog_READELF
+if test -n "$READELF"; then
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $READELF" >&5
+printf "%s\n" "$READELF" >&6; }
 else
   { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
 printf "%s\n" "no" >&6; }
 fi
 
 
-  test -n "$READELF_SFRAME" && break
+  test -n "$READELF" && break
 done
 
-if test -z "$READELF_SFRAME"; then
+if test -z "$READELF"; then
   ac_verc_fail=yes
 else
   # Found it, now check the version.
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking version of $READELF_SFRAME" >&5
-printf %s "checking version of $READELF_SFRAME... " >&6; }
-  ac_prog_version=`$READELF_SFRAME --version 2>&1 | sed -n 's/^.*GNU readelf.* \([0-9][0-9]*\.[0-9.]*\).*$/\1/p'`
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking version of $READELF" >&5
+printf %s "checking version of $READELF... " >&6; }
+  ac_prog_version=`$READELF --version 2>&1 | sed -n 's/^.*GNU readelf.* \([0-9][0-9]*\.[0-9.]*\).*$/\1/p'`
   case $ac_prog_version in
     '') ac_prog_version="v. ?.??, bad"; ac_verc_fail=yes;;
-    2.4[1-9]*|2.[5-9][0-9]*|[3-9].*|[1-9][0-9][0-9]*)
+    2.4[5-9]*|2.[5-9][0-9]*|2.[1-9][0-9][0-9]*|[3-9]*|[1-9][0-9]*)
        ac_prog_version="$ac_prog_version, ok"; ac_verc_fail=no;;
     *) ac_prog_version="$ac_prog_version, bad"; ac_verc_fail=yes;;
 
@@ -9425,12 +9436,17 @@ printf %s "checking version of $READELF_SFRAME... " >&6; }
 printf "%s\n" "$ac_prog_version" >&6; }
 fi
 if test $ac_verc_fail = yes; then
-  libc_cv_readelf_version_ok=no
+  libc_cv_sframe_readelf_version=no
 fi
 
+  if test $libc_cv_sframe_readelf_version == no; then
+    { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: in '$ac_pwd':" >&5
+printf "%s\n" "$as_me: error: in '$ac_pwd':" >&2;}
+as_fn_error $? "binutils too old to enable SFrame
+See 'config.log' for more details" "$LINENO" 5; }
+  fi
 
-# Check the current toolchain for SFrame support
-if test $libc_cv_readelf_version_ok = yes; then
+  # Check if the current toolchain supports SFrame
   { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for SFrame support" >&5
 printf %s "checking for SFrame support... " >&6; }
 if test ${libc_cv_default_sframe+y}
@@ -9455,20 +9471,20 @@ esac
 fi
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_default_sframe" >&5
 printf "%s\n" "$libc_cv_default_sframe" >&6; }
-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
-  enable_gsframe=yes
-elif test $use_sframe = yes; then
+  if test $libc_cv_default_sframe == no; then
     { { printf "%s\n" "$as_me:${as_lineno-$LINENO}: error: in '$ac_pwd':" >&5
 printf "%s\n" "$as_me: error: in '$ac_pwd':" >&2;}
 as_fn_error $? "toolchain doesn't support SFrame v2 or higher
 See 'config.log' for more details" "$LINENO" 5; }
-fi
+  fi
 
+  enable_gsframe=yes
+  printf "%s\n" "#define ENABLE_SFRAME 1" >>confdefs.h
+
+fi
+config_vars="$config_vars
+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.

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
@@ -2147,17 +2155,15 @@ EOF
     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
-  enable_gsframe=yes
-elif test $use_sframe = yes; then
+  if test $libc_cv_default_sframe == no; then
     AC_MSG_FAILURE([toolchain doesn't support SFrame v2 or higher])
+  fi
+
+  enable_gsframe=yes
+  AC_DEFINE(ENABLE_SFRAME)
 fi
-AC_SUBST(enable_gsframe)
+LIBC_CONFIG_VAR([enable-gsframe], [$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.

debug/Makefile

@@ -286,14 +286,17 @@ LDFLAGS-tst-backtrace4 = -rdynamic
 LDFLAGS-tst-backtrace5 = -rdynamic
 LDFLAGS-tst-backtrace6 = -rdynamic
 
+$(objpfx)tst-backtrace1: $(shared-thread-library)
+
 # When SFrame is enabled, make sure the dwarf unwinder is also exercised.
 ifeq ($(enable-gsframe),yes)
 dw_unwind_pair := \
-  tst-backtrace7:tst-backtrace2 \
-  tst-backtrace8:tst-backtrace3 \
-  tst-backtrace9:tst-backtrace4 \
-  tst-backtrace10:tst-backtrace5 \
-  tst-backtrace11:tst-backtrace6
+  tst-backtrace1-nosframe:tst-backtrace1 \
+  tst-backtrace2-nosframe:tst-backtrace2 \
+  tst-backtrace3-nosframe:tst-backtrace3 \
+  tst-backtrace4-nosframe:tst-backtrace4 \
+  tst-backtrace5-nosframe:tst-backtrace5 \
+  tst-backtrace6-nosframe:tst-backtrace6
 
 first_column = $(foreach pair,$(dw_unwind_pair),$(word 1,$(subst :, ,$(pair))))
 tests-dw-unwind = $(patsubst %,$(objpfx)%.out,$(first_column))
@@ -302,7 +305,7 @@ endif
 
 define make-strip-rule
 $(objpfx)$(word 1,$(subst :, ,$(1))): $(objpfx)$(word 2,$(subst :, ,$(1)))
-	strip --remove-section=.sframe $$< -o $$@
+	$(STRIP) --remove-section=.sframe $$< -o $$@
 endef
 
 $(foreach pair,$(dw_unwind_pair),$(eval $(call make-strip-rule,$(pair))))
@@ -325,6 +328,7 @@ tests = \
   backtrace-tst \
   test-stpcpy_chk \
   test-strcpy_chk \
+  tst-backtrace1 \
   tst-backtrace2 \
   tst-backtrace3 \
   tst-backtrace4 \

debug/backtrace.c

@@ -20,7 +20,9 @@
 #include <stdlib.h>
 #include <unwind.h>
 #include <unwind-link.h>
+#if ENABLE_SFRAME
 #include <sframe.h>
+#endif
 
 struct trace_arg
 {
@@ -31,6 +33,7 @@ struct trace_arg
   int size;
 };
 
+#if ENABLE_SFRAME
 /* Initialize the SFrame backtrace routine and attempt to backtrace
    the current stack using SFrame information.  For the SFrame
    backtrace to be considered valid, the tracer must return more than
@@ -64,6 +67,7 @@ do_sframe_backtrace (void **array, int size)
   frame.fp = (_Unwind_Ptr) __builtin_frame_address (0);
   return __stacktrace_sframe (array, size, &frame);
 }
+#endif
 
 static _Unwind_Reason_Code
 backtrace_helper (struct _Unwind_Context *ctx, void *a)
@@ -110,10 +114,12 @@ __backtrace (void **array, int size)
   if (size <= 0)
     return 0;
 
+#if ENABLE_SFRAME
   /* Try first the SFrame backtracer.  */
   int cnt = do_sframe_backtrace (array, size);
   if (cnt > 1)
     return cnt;
+#endif
 
   /* Try the dwarf unwinder.  */
   if (arg.unwind_link == NULL)

manual/install.texi

@@ -321,10 +321,13 @@ the build compiler.
 
 Default is to disable fortification.
 
-@item --disable-sframe
-By default, the GNU C Library is built with @option{-Wa,--gsframe} if
-the current GNU @code{binutils} supports it. You may want to use this
-option if you don't plan to use SFrame stack tracer.
+@item --enable-sframe
+Experimental option supported by some architectures, where @theglibc{}
+is built with @option{-Wa,--gsframe} if @code{binutils} supports it.
+Currently this is only supported on x86_64 and aarch64.  The option
+enables SFrame support on @code{backtrace}.
+
+Default is to disable SFrame support.
 @end table
 
 To build the library and related programs, type @code{make}.  This will

sysdeps/aarch64/configure

@@ -194,3 +194,5 @@ if test $build_mathvec = no; then
 printf "%s\n" "$as_me: WARNING: mathvec is disabled, this results in incomplete ABI." >&2;}
 fi
 
+libc_cv_support_sframe=yes
+

sysdeps/aarch64/configure.ac

@@ -31,3 +31,5 @@ fi
 if test $build_mathvec = no; then
   AC_MSG_WARN([mathvec is disabled, this results in incomplete ABI.])
 fi
+
+libc_cv_support_sframe=yes

sysdeps/generic/Makefile

@@ -21,7 +21,9 @@ CFLAGS-wordcopy.c += -Wno-uninitialized
 endif
 
 ifeq ($(subdir),elf)
+ifeq ($(enable-gsframe),yes)
 sysdep_routines += sframe-read sframe
+endif
 ifeq (yes:yes,$(build-shared):$(unwind-find-fde))
 # This is needed to support g++ v2 and v3.
 sysdep_routines += framestate unwind-pe

sysdeps/pthread/Makefile

@@ -62,7 +62,6 @@ tests += \
   tst-abstime \
   tst-atfork1 \
   tst-attr1 \
-  tst-backtrace1 \
   tst-bad-schedattr \
   tst-barrier1 \
   tst-barrier2 \

sysdeps/x86_64/configure

@@ -289,6 +289,8 @@ fi
 config_vars="$config_vars
 have-x86-apx = $libc_cv_x86_have_apx"
 
+libc_cv_support_sframe=yes
+
 test -n "$critic_missing" && as_fn_error $? "
 *** $critic_missing" "$LINENO" 5
 

sysdeps/x86_64/configure.ac

@@ -104,5 +104,7 @@ if test $libc_cv_x86_have_apx = yes; then
 fi
 LIBC_CONFIG_VAR([have-x86-apx], [$libc_cv_x86_have_apx])
 
+libc_cv_support_sframe=yes
+
 test -n "$critic_missing" && AC_MSG_ERROR([
 *** $critic_missing])