[SFrame-V3] ld: add --discard-sframe command line option

Add a new command line option --discard-sframe to the linker.
This option allows users to prevent the linker from generating an output
.sframe section.

The rationale for this option is: Consider the case when say, the distro
is shipped with SFrame sections in the installed binaries/libraries. A
user application using these installed libraries, but not enabling
.sframe for itself just yet, will see an output .sframe corresponding to
the pulled in libraries.  This is "partial" .sframe information for the
application.  Adding such an option to the linker, gives user a way to
turn off the .sframe section completely without relying on a linker
script.

Previously, the existing --no-ld-generated-unwind-info option
controlled whether (not just .eh_frame for PLT entries, but also) SFrame
for PLT entries. The new command line option,
--discard-sframe now decouples SFrame from other unwind
formats (like .eh_frame), allowing for more control over the output
binary's SFrame data.

The option is added for architectures that currently support SFrame:
AArch64, s390x, and x86_64.

bfd/
	* elf-sframe.c (_bfd_elf_parse_sframe): Mark with SEC_EXCLUDE if
	--discard-sframe is in effect.
	* elf64-s390.c (elf_s390_create_dynamic_sections): Use
	discard_sframe to guard .sframe section creation.
	* elfxx-x86.c (_bfd_x86_elf_link_setup_gnu_properties): Likewise.
include/
	* bfdlink.h (struct bfd_link_info): Add discard_sframe bitfield.
ld/
	* ldlex.h (enum option_values): Add OPTION_NO_LD_SFRAME_INFO.
	* lexsup.c (elf_sframe_list_options): New function.
	(ld_list_options): Add sframe_info argument. Update callers.
	* ld.texi: Update documentation.
	* emulparams/sframe-info.sh: New file.
	* emultempl/aarch64elf.em: Add --discard-sframe option
	listing and handling.
	* emulparams/elf64_s390.sh: Likewise.
	* emulparams/elf_x86_64.sh: Likewise.
	* Makefile.am: Update to handle sframe-info.sh and new list options.
	* configure.ac: Handle SFRAME_INFO target variable.
	* Makefile.in: Regenerate.
	* configure: Regenerate.
ld/testsuite/
	* ld-x86-64/x86-64.exp: New test.
	* ld-x86-64/sframe-command-line-1.d: New test.
	* ld-aarch64/aarch64-elf.exp: New test.
	* ld-s390/s390.exp: New test.
	* ld-x86-64/x86-64.exp: New test.
	* ld-aarch64/sframe-command-line-1.d: New test.
	* ld-s390/sframe-command-line-1.d: New test.
	* ld-x86-64/sframe-command-line-1.d: New test.

bfd/elf-sframe.c

@@ -211,6 +211,9 @@ _bfd_elf_parse_sframe (bfd *abfd,
   bfd_size_type sf_size;
   int decerr = 0;
 
+  if (info->discard_sframe)
+    sec->flags |= SEC_EXCLUDE;
+
   /* Prior versions of assembler and ld were generating SFrame sections with
      section type SHT_PROGBITS.  Issue an error for lack of support for such
      objects now.  Even if section size is zero, a valid section type is

bfd/elf64-s390.c

@@ -4309,7 +4309,7 @@ elf_s390_create_dynamic_sections (bfd *dynobj,
         }
 
       /* Create .sframe section for .plt section.  */
-      if (!info->no_ld_generated_unwind_info)
+      if (!info->discard_sframe)
 	{
 	  flagword flags = (SEC_ALLOC | SEC_LOAD | SEC_READONLY
 			    | SEC_HAS_CONTENTS | SEC_IN_MEMORY

bfd/elfxx-x86.c

@@ -4827,7 +4827,7 @@ _bfd_x86_elf_link_setup_gnu_properties
 	}
 
       /* .sframe sections are emitted for AMD64 ABI only.  */
-      if (ABI_64_P (info->output_bfd) && !info->no_ld_generated_unwind_info)
+      if (ABI_64_P (info->output_bfd) && !info->discard_sframe)
 	{
 	  flagword flags = (SEC_ALLOC | SEC_LOAD | SEC_READONLY
 			    | SEC_HAS_CONTENTS | SEC_IN_MEMORY

include/bfdlink.h

@@ -475,6 +475,10 @@ struct bfd_link_info
      linker created sections, TRUE if it should be omitted.  */
   unsigned int no_ld_generated_unwind_info: 1;
 
+  /* TRUE if no .sframe stack trace info should be generated for the output.
+     This includes linker generated SFrame info as well.  */
+  unsigned int discard_sframe: 1;
+
   /* TRUE if BFD should generate a "task linked" object file,
      similar to relocatable but also with globals converted to
      statics.  */

ld/Makefile.am

@@ -42,7 +42,8 @@ ZLIBINC = @zlibinc@
 
 ELF_CFLAGS=-DELF_LIST_OPTIONS=@elf_list_options@ \
 	   -DELF_SHLIB_LIST_OPTIONS=@elf_shlib_list_options@ \
-	   -DELF_PLT_UNWIND_LIST_OPTIONS=@elf_plt_unwind_list_options@
+	   -DELF_PLT_UNWIND_LIST_OPTIONS=@elf_plt_unwind_list_options@ \
+	   -DELF_SFRAME_LIST_OPTIONS=@elf_sframe_list_options@
 WARN_CFLAGS = @WARN_CFLAGS@
 NO_WERROR = @NO_WERROR@
 AM_CFLAGS = $(WARN_CFLAGS) $(ELF_CFLAGS) $(JANSSON_CFLAGS) $(ZSTD_CFLAGS)

ld/Makefile.in

@@ -520,6 +520,7 @@ docdir = @docdir@
 dvidir = @dvidir@
 elf_list_options = @elf_list_options@
 elf_plt_unwind_list_options = @elf_plt_unwind_list_options@
+elf_sframe_list_options = @elf_sframe_list_options@
 elf_shlib_list_options = @elf_shlib_list_options@
 enable_initfini_array = @enable_initfini_array@
 enable_libctf = @enable_libctf@
@@ -579,7 +580,8 @@ ZLIB = @zlibdir@ -lz
 ZLIBINC = @zlibinc@
 ELF_CFLAGS = -DELF_LIST_OPTIONS=@elf_list_options@ \
 	   -DELF_SHLIB_LIST_OPTIONS=@elf_shlib_list_options@ \
-	   -DELF_PLT_UNWIND_LIST_OPTIONS=@elf_plt_unwind_list_options@
+	   -DELF_PLT_UNWIND_LIST_OPTIONS=@elf_plt_unwind_list_options@ \
+	   -DELF_SFRAME_LIST_OPTIONS=@elf_sframe_list_options@
 
 AM_CFLAGS = $(WARN_CFLAGS) $(ELF_CFLAGS) $(JANSSON_CFLAGS) $(ZSTD_CFLAGS)
 

ld/configure

@@ -644,6 +644,7 @@ EMUL_EXTRA_OFILES
 EMULATION_OFILES
 TDIRS
 EMUL
+elf_sframe_list_options
 elf_plt_unwind_list_options
 elf_shlib_list_options
 elf_list_options
@@ -11893,7 +11894,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11896 "configure"
+#line 11897 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11999,7 +12000,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 12002 "configure"
+#line 12003 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -19211,6 +19212,7 @@ TDIRS=
 elf_list_options=false
 elf_shlib_list_options=false
 elf_plt_unwind_list_options=false
+elf_sframe_list_options=false
 for targ_alias in `echo $target_alias $enable_targets | sed 's/,/ /g'`
 do
   if test "$targ_alias" = "all"; then
@@ -19218,6 +19220,7 @@ do
     elf_list_options=true
     elf_shlib_list_options=true
     elf_plt_unwind_list_options=true
+    elf_sframe_list_options=true
   else
     # Canonicalize the secondary target names.
     result=`$ac_config_sub $targ_alias 2>/dev/null`
@@ -19273,6 +19276,9 @@ tdir_$i=$result"
 	    if test x${PLT_UNWIND} = xyes; then
 	      elf_plt_unwind_list_options=true
 	    fi
+	    if test x${SFRAME_INFO} = xyes; then
+	      elf_sframe_list_options=true
+	    fi
 	  fi
 	  ;;
 	esac
@@ -19481,6 +19487,7 @@ _ACEOF
 
 
 
+
 if test x${all_targets} = xtrue; then
   if test x${have_64_bit_bfd} = xyes; then
     EMULATION_OFILES='$(ALL_EMULATIONS) $(ALL_64_EMULATIONS)'

ld/configure.ac

@@ -506,6 +506,7 @@ TDIRS=
 elf_list_options=false
 elf_shlib_list_options=false
 elf_plt_unwind_list_options=false
+elf_sframe_list_options=false
 for targ_alias in `echo $target_alias $enable_targets | sed 's/,/ /g'`
 do
   if test "$targ_alias" = "all"; then
@@ -513,6 +514,7 @@ do
     elf_list_options=true
     elf_shlib_list_options=true
     elf_plt_unwind_list_options=true
+    elf_sframe_list_options=true
   else
     # Canonicalize the secondary target names.
     result=`$ac_config_sub $targ_alias 2>/dev/null`
@@ -568,6 +570,9 @@ tdir_$i=$result"
 	    if test x${PLT_UNWIND} = xyes; then
 	      elf_plt_unwind_list_options=true
 	    fi
+	    if test x${SFRAME_INFO} = xyes; then
+	      elf_sframe_list_options=true
+	    fi
 	  fi
 	  ;;
 	esac
@@ -730,6 +735,7 @@ AC_DEFINE_UNQUOTED([DEFAULT_EMIT_GNU_HASH],
 AC_SUBST(elf_list_options)
 AC_SUBST(elf_shlib_list_options)
 AC_SUBST(elf_plt_unwind_list_options)
+AC_SUBST(elf_sframe_list_options)
 AC_SUBST(EMUL)
 
 AC_SUBST(TDIRS)

ld/emulparams/elf64_s390.sh

@@ -1,4 +1,5 @@
 source_sh ${srcdir}/emulparams/plt_unwind.sh
+source_sh ${srcdir}/emulparams/sframe-info.sh
 SCRIPT_NAME=elf
 ELFSIZE=64
 OUTPUT_FORMAT="elf64-s390"

ld/emulparams/elf_x86_64.sh

@@ -1,4 +1,5 @@
 source_sh ${srcdir}/emulparams/plt_unwind.sh
+source_sh ${srcdir}/emulparams/sframe-info.sh
 source_sh ${srcdir}/emulparams/extern_protected_data.sh
 source_sh ${srcdir}/emulparams/dynamic_undefined_weak.sh
 source_sh ${srcdir}/emulparams/reloc_overflow.sh

ld/emulparams/sframe-info.sh

@@ -0,0 +1,15 @@
+SFRAME_INFO=yes
+
+PARSE_AND_LIST_LONGOPTS_SFRAME='
+  {"discard-sframe", no_argument, NULL,
+   OPTION_DISCARD_SFRAME},
+'
+
+PARSE_AND_LIST_ARGS_CASES_SFRAME='
+    case OPTION_DISCARD_SFRAME:
+      link_info.discard_sframe = true;
+      break;
+'
+
+PARSE_AND_LIST_LONGOPTS="$PARSE_AND_LIST_LONGOPTS $PARSE_AND_LIST_LONGOPTS_SFRAME"
+PARSE_AND_LIST_ARGS_CASES="$PARSE_AND_LIST_ARGS_CASES $PARSE_AND_LIST_ARGS_CASES_SFRAME"

ld/emultempl/aarch64elf.em

@@ -487,6 +487,7 @@ PARSE_AND_LIST_LONGOPTS='
   { "fix-cortex-a53-835769", no_argument, NULL, OPTION_FIX_ERRATUM_835769},
   { "fix-cortex-a53-843419", optional_argument, NULL, OPTION_FIX_ERRATUM_843419},
   { "no-apply-dynamic-relocs", no_argument, NULL, OPTION_NO_APPLY_DYNAMIC_RELOCS},
+  { "discard-sframe", no_argument, NULL, OPTION_DISCARD_SFRAME},
 '
 
 PARSE_AND_LIST_OPTIONS='
@@ -495,6 +496,7 @@ PARSE_AND_LIST_OPTIONS='
   fprintf (file, _("  --no-wchar-size-warning     Don'\''t warn about objects with incompatible\n"
 		   "                                wchar_t sizes\n"));
   fprintf (file, _("  --pic-veneer                Always generate PIC interworking veneers\n"));
+  fprintf (file, _("  --discard-sframe            Don'\''t generate SFrame stack trace info in output\n"));
   fprintf (file, _("\
   --stub-group-size=N         Maximum size of a group of input sections that\n\
                                 can be handled by one stub section.  A negative\n\
@@ -632,6 +634,11 @@ PARSE_AND_LIST_ARGS_CASES='
 	  fatal (_("%P: invalid number `%s'\''\n"), optarg);
       }
       break;
+
+    case OPTION_DISCARD_SFRAME:
+      link_info.discard_sframe = true;
+      break;
+
 '
 
 # We have our own before_allocation etc. functions, but they call

ld/ld.texi

@@ -3251,9 +3251,13 @@ section and ELF @code{PT_GNU_EH_FRAME} segment header.
 @item --no-ld-generated-unwind-info
 Request creation of @code{.eh_frame} unwind info for linker
 generated code sections like PLT.  This option is on by default
-if linker generated unwind info is supported.  This option also
-controls the generation of @code{.sframe} stack trace info for linker
-generated code sections like PLT.
+if linker generated unwind info is supported.
+
+@kindex --discard-sframe
+@item --discard-sframe
+Discard @code{.sframe} stack trace info from the output.  This option also
+prohibits the creation of SFrame stack trace data for linker generated code
+sections like PLT.  This option is off by default.
 
 @kindex --enable-new-dtags
 @kindex --disable-new-dtags

ld/ldlex.h

@@ -215,6 +215,8 @@ enum option_values
   /* Used by emulparams/plt_unwind.sh.  */
   OPTION_LD_GENERATED_UNWIND_INFO,
   OPTION_NO_LD_GENERATED_UNWIND_INFO,
+  /* Used by emulparams/sframe-info.sh.  */
+  OPTION_DISCARD_SFRAME,
   /* Used by emultempl/aarch64elf.em.  */
   OPTION_FIX_ERRATUM_835769,
   OPTION_FIX_ERRATUM_843419,

ld/lexsup.c

@@ -2364,13 +2364,23 @@ elf_plt_unwind_list_options (FILE *file)
 }
 
 static void
-ld_list_options (FILE *file, bool elf, bool shlib, bool plt_unwind)
+elf_sframe_list_options (FILE *file)
+{
+  fprintf (file, _("\
+  --discard-sframe            Don't generate SFrame stack trace info in output\n"));
+}
+
+static void
+ld_list_options (FILE *file, bool elf, bool shlib, bool plt_unwind,
+		 bool sframe_info)
 {
   if (!elf)
     return;
   printf (_("ELF emulations:\n"));
   if (plt_unwind)
     elf_plt_unwind_list_options (file);
+  if (sframe_info)
+    elf_sframe_list_options (file);
   elf_static_list_options (file);
   if (shlib)
     elf_shlib_list_options (file);
@@ -2495,7 +2505,8 @@ help (void)
   /* xgettext:c-format */
   printf (_("%s: emulation specific options:\n"), program_name);
   ld_list_options (stdout, ELF_LIST_OPTIONS, ELF_SHLIB_LIST_OPTIONS,
-		   ELF_PLT_UNWIND_LIST_OPTIONS);
+		   ELF_PLT_UNWIND_LIST_OPTIONS,
+		   ELF_SFRAME_LIST_OPTIONS);
   ldemul_list_emulation_options (stdout);
   printf ("\n");
 

ld/testsuite/ld-aarch64/aarch64-elf.exp

@@ -430,4 +430,5 @@ if { [supports_dt_relr] } {
 
 if { ![skip_sframe_tests] } {
   run_dump_test "sframe-simple-1"
+  run_dump_test "sframe-command-line-1"
 }

ld/testsuite/ld-aarch64/sframe-command-line-1.d

@@ -0,0 +1,8 @@
+#as: --gsframe
+#source: sframe-foo.s
+#source: sframe-bar.s
+#readelf: --sframe
+#ld: -shared --discard-sframe
+#name: Command line option --discard-sframe
+
+Section '.sframe' has no debugging data.

ld/testsuite/ld-s390/s390.exp

@@ -192,5 +192,6 @@ if [istarget "s390x-*-*"] {
     if { ![skip_sframe_tests] } {
 	run_dump_test "sframe-simple-1"
 	run_dump_test "sframe-plt-1"
+	run_dump_test "sframe-command-line-1"
     }
 }

ld/testsuite/ld-s390/sframe-command-line-1.d

@@ -0,0 +1,8 @@
+#as: --gsframe
+#source: sframe-foo.s
+#source: sframe-bar.s
+#readelf: --sframe
+#ld: -shared --no-rosegment --discard-sframe
+#name: Command line option --discard-sframe
+
+Section '.sframe' has no debugging data.

ld/testsuite/ld-x86-64/sframe-command-line-1.d

@@ -0,0 +1,8 @@
+#as: --gsframe
+#source: sframe-foo.s
+#source: sframe-bar.s
+#readelf: --sframe
+#ld: -shared --no-rosegment -z separate-code --discard-sframe
+#name: Command line option --discard-sframe
+
+Section '.sframe' has no debugging data.

ld/testsuite/ld-x86-64/x86-64.exp

@@ -587,6 +587,7 @@ run_dump_test "tls-le-pic-3-x32"
 
 if { ![skip_sframe_tests] } {
     run_dump_test "sframe-simple-1"
+    run_dump_test "sframe-command-line-1"
     run_dump_test "sframe-reloc-1"
     run_dump_test "sframe-plt-1"
     run_dump_test "sframe-ibt-plt-1"