binutils, gdb: support zstd compressed debug sections

PR29397 PR29563: Add new configure option --with-zstd which defaults to
auto.  If pkgconfig/libzstd.pc is found, define HAVE_ZSTD and support
zstd compressed debug sections for most tools.

* bfd: for addr2line, objdump --dwarf, gdb, etc
* gas: support --compress-debug-sections=zstd
* ld: support ELFCOMPRESS_ZSTD input and --compress-debug-sections=zstd
* objcopy: support ELFCOMPRESS_ZSTD input for
  --decompress-debug-sections and --compress-debug-sections=zstd
* gdb: support ELFCOMPRESS_ZSTD input.  The bfd change references zstd
  symbols, so gdb has to link against -lzstd in this patch.

If zstd is not supported, ELFCOMPRESS_ZSTD input triggers an error.  We
can avoid HAVE_ZSTD if binutils-gdb imports zstd/ like zlib/, but this
is too heavyweight, so don't do it for now.

```
% ld/ld-new a.o
ld/ld-new: a.o: section .debug_abbrev is compressed with zstd, but BFD is not built with zstd support
...

% ld/ld-new a.o --compress-debug-sections=zstd
ld/ld-new: --compress-debug-sections=zstd: ld is not built with zstd support

% binutils/objcopy --compress-debug-sections=zstd a.o b.o
binutils/objcopy: --compress-debug-sections=zstd: binutils is not built with zstd support

% binutils/objcopy b.o --decompress-debug-sections
binutils/objcopy: zstd.o: section .debug_abbrev is compressed with zstd, but BFD is not built with zstd support
...
```

13 files changed, 324 insertions, 141 deletions

diff --git a/ld/Makefile.am b/ld/Makefile.am
index d31021c..bbe25f3 100644
--- a/ld/Makefile.am
+++ b/ld/Makefile.am
@@ -45,7 +45,7 @@ ELF_CLFAGS=-DELF_LIST_OPTIONS=@elf_list_options@ \
 	   -DELF_PLT_UNWIND_LIST_OPTIONS=@elf_plt_unwind_list_options@
 WARN_CFLAGS = @WARN_CFLAGS@
 NO_WERROR = @NO_WERROR@
-AM_CFLAGS = $(WARN_CFLAGS) $(ELF_CLFAGS) $(JANSSON_CFLAGS)
+AM_CFLAGS = $(WARN_CFLAGS) $(ELF_CLFAGS) $(JANSSON_CFLAGS) $(ZSTD_CFLAGS)
 
 # We put the scripts in the directory $(scriptdir)/ldscripts.
 # We can't put the scripts in $(datadir) because the SEARCH_DIR
@@ -959,7 +959,8 @@ ld_new_SOURCES = ldgram.y ldlex-wrapper.c lexsup.c ldlang.c mri.c ldctor.c ldmai
 	ldbuildid.c
 ld_new_DEPENDENCIES = $(EMULATION_OFILES) $(EMUL_EXTRA_OFILES) \
 		      $(BFDLIB) $(LIBCTF) $(LIBIBERTY) $(LIBINTL_DEP) $(JANSSON_LIBS)
-ld_new_LDADD = $(EMULATION_OFILES) $(EMUL_EXTRA_OFILES) $(BFDLIB) $(LIBCTF) $(LIBIBERTY) $(LIBINTL) $(ZLIB) $(JANSSON_LIBS)
+ld_new_LDADD = $(EMULATION_OFILES) $(EMUL_EXTRA_OFILES) $(BFDLIB) $(LIBCTF) \
+	       $(LIBIBERTY) $(LIBINTL) $(ZLIB) $(ZSTD_LIBS) $(JANSSON_LIBS)
 
 # Dependency tracking for the generated emulation files.
 EXTRA_ld_new_SOURCES += $(ALL_EMULATION_SOURCES) $(ALL_64_EMULATION_SOURCES)
diff --git a/ld/Makefile.in b/ld/Makefile.in
index ee0c98f..400eed2 100644
--- a/ld/Makefile.in
+++ b/ld/Makefile.in
@@ -126,7 +126,8 @@ am__aclocal_m4_deps = $(top_srcdir)/../bfd/acinclude.m4 \
 	$(top_srcdir)/../config/plugins.m4 \
 	$(top_srcdir)/../config/po.m4 \
 	$(top_srcdir)/../config/progtest.m4 \
-	$(top_srcdir)/../config/zlib.m4 $(top_srcdir)/../libtool.m4 \
+	$(top_srcdir)/../config/zlib.m4 \
+	$(top_srcdir)/../config/zstd.m4 $(top_srcdir)/../libtool.m4 \
 	$(top_srcdir)/../ltoptions.m4 $(top_srcdir)/../ltsugar.m4 \
 	$(top_srcdir)/../ltversion.m4 $(top_srcdir)/../lt~obsolete.m4 \
 	$(top_srcdir)/../bfd/version.m4 $(top_srcdir)/configure.ac
@@ -477,6 +478,8 @@ WARN_WRITE_STRINGS = @WARN_WRITE_STRINGS@
 XGETTEXT = @XGETTEXT@
 YACC = `if [ -f ../bison/bison ]; then echo ../bison/bison -y -L$(srcdir)/../bison/; else echo @YACC@; fi`
 YFLAGS = -d
+ZSTD_CFLAGS = @ZSTD_CFLAGS@
+ZSTD_LIBS = @ZSTD_LIBS@
 abs_builddir = @abs_builddir@
 abs_srcdir = @abs_srcdir@
 abs_top_builddir = @abs_top_builddir@
@@ -564,7 +567,7 @@ ELF_CLFAGS = -DELF_LIST_OPTIONS=@elf_list_options@ \
 	   -DELF_SHLIB_LIST_OPTIONS=@elf_shlib_list_options@ \
 	   -DELF_PLT_UNWIND_LIST_OPTIONS=@elf_plt_unwind_list_options@
 
-AM_CFLAGS = $(WARN_CFLAGS) $(ELF_CLFAGS) $(JANSSON_CFLAGS)
+AM_CFLAGS = $(WARN_CFLAGS) $(ELF_CLFAGS) $(JANSSON_CFLAGS) $(ZSTD_CFLAGS)
 
 # We put the scripts in the directory $(scriptdir)/ldscripts.
 # We can't put the scripts in $(datadir) because the SEARCH_DIR
@@ -1011,7 +1014,9 @@ ld_new_SOURCES = ldgram.y ldlex-wrapper.c lexsup.c ldlang.c mri.c ldctor.c ldmai
 ld_new_DEPENDENCIES = $(EMULATION_OFILES) $(EMUL_EXTRA_OFILES) \
 		      $(BFDLIB) $(LIBCTF) $(LIBIBERTY) $(LIBINTL_DEP) $(JANSSON_LIBS)
 
-ld_new_LDADD = $(EMULATION_OFILES) $(EMUL_EXTRA_OFILES) $(BFDLIB) $(LIBCTF) $(LIBIBERTY) $(LIBINTL) $(ZLIB) $(JANSSON_LIBS)
+ld_new_LDADD = $(EMULATION_OFILES) $(EMUL_EXTRA_OFILES) $(BFDLIB) $(LIBCTF) \
+	       $(LIBIBERTY) $(LIBINTL) $(ZLIB) $(ZSTD_LIBS) $(JANSSON_LIBS)
+
 #
 #
 # Build a dummy plugin using libtool.
diff --git a/ld/NEWS b/ld/NEWS
index 355752e..dfe2690 100644
--- a/ld/NEWS
+++ b/ld/NEWS
@@ -1,5 +1,8 @@
 -*- text -*-
 
+* ld now supports zstd compressed debug sections.  The new option
+  --compress-debug-sections=zstd compresses debug sections with zstd.
+
 Changes in 2.39:
 
 * The ELF linker will now generate a warning message if the stack is made
diff --git a/ld/aclocal.m4 b/ld/aclocal.m4
index d20c542..893e973 100644
--- a/ld/aclocal.m4
+++ b/ld/aclocal.m4
@@ -1203,6 +1203,7 @@ m4_include([../config/plugins.m4])
 m4_include([../config/po.m4])
 m4_include([../config/progtest.m4])
 m4_include([../config/zlib.m4])
+m4_include([../config/zstd.m4])
 m4_include([../libtool.m4])
 m4_include([../ltoptions.m4])
 m4_include([../ltsugar.m4])
diff --git a/ld/config.in b/ld/config.in
index 0ccd79d..3916740 100644
--- a/ld/config.in
+++ b/ld/config.in
@@ -162,6 +162,9 @@
 /* Define to 1 if you have the <windows.h> header file. */
 #undef HAVE_WINDOWS_H
 
+/* Define to 1 if zstd is enabled. */
+#undef HAVE_ZSTD
+
 /* Define to the sub-directory in which libtool stores uninstalled libraries.
    */
 #undef LT_OBJDIR
diff --git a/ld/configure b/ld/configure
index 4efe3ef..9dd3ed5 100755
--- a/ld/configure
+++ b/ld/configure
@@ -646,6 +646,8 @@ elf_plt_unwind_list_options
 elf_shlib_list_options
 elf_list_options
 STRINGIFY
+ZSTD_LIBS
+ZSTD_CFLAGS
 zlibinc
 zlibdir
 NATIVE_LIB_DIRS
@@ -679,9 +681,6 @@ WARN_CFLAGS_FOR_BUILD
 WARN_CFLAGS
 JANSSON_LIBS
 JANSSON_CFLAGS
-PKG_CONFIG_LIBDIR
-PKG_CONFIG_PATH
-PKG_CONFIG
 enable_libctf
 ENABLE_LIBCTF_FALSE
 ENABLE_LIBCTF_TRUE
@@ -711,6 +710,9 @@ LD
 FGREP
 SED
 LIBTOOL
+PKG_CONFIG_LIBDIR
+PKG_CONFIG_PATH
+PKG_CONFIG
 EGREP
 CPP
 GREP
@@ -855,6 +857,7 @@ enable_werror
 enable_build_warnings
 enable_nls
 with_system_zlib
+with_zstd
 '
       ac_precious_vars='build_alias
 host_alias
@@ -868,14 +871,16 @@ CXX
 CXXFLAGS
 CCC
 CPP
-CXXCPP
 PKG_CONFIG
 PKG_CONFIG_PATH
 PKG_CONFIG_LIBDIR
+CXXCPP
 JANSSON_CFLAGS
 JANSSON_LIBS
 YACC
-YFLAGS'
+YFLAGS
+ZSTD_CFLAGS
+ZSTD_LIBS'
 
 
 # Initialize some variables set by options.
@@ -1552,6 +1557,8 @@ Optional Packages:
   --with-lib-path=dir1:dir2...  set default LIB_PATH
   --with-sysroot=DIR Search for usr/lib et al within DIR.
   --with-system-zlib      use installed libz
+  --with-zstd             support zstd compressed debug sections
+                          (default=auto)
 
 Some influential environment variables:
   CC          C compiler command
@@ -1564,12 +1571,12 @@ Some influential environment variables:
   CXX         C++ compiler command
   CXXFLAGS    C++ compiler flags
   CPP         C preprocessor
-  CXXCPP      C++ preprocessor
   PKG_CONFIG  path to pkg-config utility
   PKG_CONFIG_PATH
               directories to add to pkg-config's search path
   PKG_CONFIG_LIBDIR
               path overriding pkg-config's built-in search path
+  CXXCPP      C++ preprocessor
   JANSSON_CFLAGS
               C compiler flags for JANSSON, overriding pkg-config
   JANSSON_LIBS
@@ -1580,6 +1587,8 @@ Some influential environment variables:
   YFLAGS      The list of arguments that will be passed by default to $YACC.
               This script will default YFLAGS to the empty string to avoid a
               default value of `-d' given by some make applications.
+  ZSTD_CFLAGS C compiler flags for ZSTD, overriding pkg-config
+  ZSTD_LIBS   linker flags for ZSTD, overriding pkg-config
 
 Use these variables to override the choices made by `configure' or to help
 it to find libraries and programs with nonstandard names/locations.
@@ -5388,6 +5397,126 @@ $as_echo "$ac_cv_safe_to_define___extensions__" >&6; }
 
 
 
+
+
+
+
+
+
+if test "x$ac_cv_env_PKG_CONFIG_set" != "xset"; then
+	if test -n "$ac_tool_prefix"; then
+  # Extract the first word of "${ac_tool_prefix}pkg-config", so it can be a program name with args.
+set dummy ${ac_tool_prefix}pkg-config; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_path_PKG_CONFIG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  case $PKG_CONFIG in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_PKG_CONFIG="$PKG_CONFIG" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_path_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  ;;
+esac
+fi
+PKG_CONFIG=$ac_cv_path_PKG_CONFIG
+if test -n "$PKG_CONFIG"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PKG_CONFIG" >&5
+$as_echo "$PKG_CONFIG" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+fi
+if test -z "$ac_cv_path_PKG_CONFIG"; then
+  ac_pt_PKG_CONFIG=$PKG_CONFIG
+  # Extract the first word of "pkg-config", so it can be a program name with args.
+set dummy pkg-config; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_path_ac_pt_PKG_CONFIG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  case $ac_pt_PKG_CONFIG in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_ac_pt_PKG_CONFIG="$ac_pt_PKG_CONFIG" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_path_ac_pt_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  ;;
+esac
+fi
+ac_pt_PKG_CONFIG=$ac_cv_path_ac_pt_PKG_CONFIG
+if test -n "$ac_pt_PKG_CONFIG"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_pt_PKG_CONFIG" >&5
+$as_echo "$ac_pt_PKG_CONFIG" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+  if test "x$ac_pt_PKG_CONFIG" = x; then
+    PKG_CONFIG=""
+  else
+    case $cross_compiling:$ac_tool_warned in
+yes:)
+{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: using cross tools not prefixed with host triplet" >&5
+$as_echo "$as_me: WARNING: using cross tools not prefixed with host triplet" >&2;}
+ac_tool_warned=yes ;;
+esac
+    PKG_CONFIG=$ac_pt_PKG_CONFIG
+  fi
+else
+  PKG_CONFIG="$ac_cv_path_PKG_CONFIG"
+fi
+
+fi
+if test -n "$PKG_CONFIG"; then
+	_pkg_min_version=0.9.0
+	{ $as_echo "$as_me:${as_lineno-$LINENO}: checking pkg-config is at least version $_pkg_min_version" >&5
+$as_echo_n "checking pkg-config is at least version $_pkg_min_version... " >&6; }
+	if $PKG_CONFIG --atleast-pkgconfig-version $_pkg_min_version; then
+		{ $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+	else
+		{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+		PKG_CONFIG=""
+	fi
+fi
+
 case `pwd` in
   *\ * | *\	*)
     { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: Libtool does not cope well with whitespace in \`pwd\`" >&5
@@ -11491,7 +11620,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11494 "configure"
+#line 11623 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11597,7 +11726,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11600 "configure"
+#line 11729 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -15585,126 +15714,6 @@ else
 fi
 
 
-
-
-
-
-
-
-
-if test "x$ac_cv_env_PKG_CONFIG_set" != "xset"; then
-	if test -n "$ac_tool_prefix"; then
-  # Extract the first word of "${ac_tool_prefix}pkg-config", so it can be a program name with args.
-set dummy ${ac_tool_prefix}pkg-config; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_path_PKG_CONFIG+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  case $PKG_CONFIG in
-  [\\/]* | ?:[\\/]*)
-  ac_cv_path_PKG_CONFIG="$PKG_CONFIG" # Let the user override the test with a path.
-  ;;
-  *)
-  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_path_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-  ;;
-esac
-fi
-PKG_CONFIG=$ac_cv_path_PKG_CONFIG
-if test -n "$PKG_CONFIG"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PKG_CONFIG" >&5
-$as_echo "$PKG_CONFIG" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-
-fi
-if test -z "$ac_cv_path_PKG_CONFIG"; then
-  ac_pt_PKG_CONFIG=$PKG_CONFIG
-  # Extract the first word of "pkg-config", so it can be a program name with args.
-set dummy pkg-config; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_path_ac_pt_PKG_CONFIG+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  case $ac_pt_PKG_CONFIG in
-  [\\/]* | ?:[\\/]*)
-  ac_cv_path_ac_pt_PKG_CONFIG="$ac_pt_PKG_CONFIG" # Let the user override the test with a path.
-  ;;
-  *)
-  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_path_ac_pt_PKG_CONFIG="$as_dir/$ac_word$ac_exec_ext"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-  ;;
-esac
-fi
-ac_pt_PKG_CONFIG=$ac_cv_path_ac_pt_PKG_CONFIG
-if test -n "$ac_pt_PKG_CONFIG"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_pt_PKG_CONFIG" >&5
-$as_echo "$ac_pt_PKG_CONFIG" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-  if test "x$ac_pt_PKG_CONFIG" = x; then
-    PKG_CONFIG=""
-  else
-    case $cross_compiling:$ac_tool_warned in
-yes:)
-{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: using cross tools not prefixed with host triplet" >&5
-$as_echo "$as_me: WARNING: using cross tools not prefixed with host triplet" >&2;}
-ac_tool_warned=yes ;;
-esac
-    PKG_CONFIG=$ac_pt_PKG_CONFIG
-  fi
-else
-  PKG_CONFIG="$ac_cv_path_PKG_CONFIG"
-fi
-
-fi
-if test -n "$PKG_CONFIG"; then
-	_pkg_min_version=0.9.0
-	{ $as_echo "$as_me:${as_lineno-$LINENO}: checking pkg-config is at least version $_pkg_min_version" >&5
-$as_echo_n "checking pkg-config is at least version $_pkg_min_version... " >&6; }
-	if $PKG_CONFIG --atleast-pkgconfig-version $_pkg_min_version; then
-		{ $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
-$as_echo "yes" >&6; }
-	else
-		{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-		PKG_CONFIG=""
-	fi
-fi
 if test "x$enable_jansson" != "xno"; then :
 
 pkg_failed=no
@@ -17041,8 +17050,8 @@ $as_echo "#define HAVE_DECL_GETOPT 1" >>confdefs.h
 
 fi
 
-# Link in zlib if we can.  This allows us to read and write
-# compressed CTF sections.
+# Link in zlib/zstd if we can.  This allows us to read and write
+# compressed debug sections.
 
   # Use the system's zlib library.
   zlibdir="-L\$(top_builddir)/../zlib"
@@ -17061,6 +17070,127 @@ fi
 
 
 
+
+# Check whether --with-zstd was given.
+if test "${with_zstd+set}" = set; then :
+  withval=$with_zstd;
+else
+  with_zstd=auto
+fi
+
+
+if test "$with_zstd" != no; then :
+
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
+$as_echo_n "checking for libzstd... " >&6; }
+
+if test -n "$ZSTD_CFLAGS"; then
+    pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$ZSTD_LIBS"; then
+    pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+if test $pkg_failed = no; then
+  pkg_save_LDFLAGS="$LDFLAGS"
+  LDFLAGS="$LDFLAGS $pkg_cv_ZSTD_LIBS"
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+
+else
+  pkg_failed=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+  LDFLAGS=$pkg_save_LDFLAGS
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+        else
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$ZSTD_PKG_ERRORS" >&5
+
+
+    if test "$with_zstd" = yes; then
+      as_fn_error $? "--with-zstd was given, but pkgconfig/libzstd.pc is not found" "$LINENO" 5
+    fi
+
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+    if test "$with_zstd" = yes; then
+      as_fn_error $? "--with-zstd was given, but pkgconfig/libzstd.pc is not found" "$LINENO" 5
+    fi
+
+else
+	ZSTD_CFLAGS=$pkg_cv_ZSTD_CFLAGS
+	ZSTD_LIBS=$pkg_cv_ZSTD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+
+$as_echo "#define HAVE_ZSTD 1" >>confdefs.h
+
+
+fi
+
+fi
+
+
 # When converting linker scripts into strings for use in emulation
 # files, use astring.sed if the compiler supports ANSI string
 # concatenation, or ostring.sed otherwise.  This is to support the
diff --git a/ld/configure.ac b/ld/configure.ac
index 8a8bfc9..f1b2f98 100644
--- a/ld/configure.ac
+++ b/ld/configure.ac
@@ -34,6 +34,7 @@ AC_PROG_GREP
 AC_GNU_SOURCE
 AC_USE_SYSTEM_EXTENSIONS
 AC_PROG_INSTALL
+PKG_PROG_PKG_CONFIG
 
 LT_INIT
 ACX_LARGEFILE
@@ -377,9 +378,10 @@ if test $ld_cv_decl_getopt_unistd_h = yes; then
 	    [Is the prototype for getopt in <unistd.h> in the expected format?])
 fi
 
-# Link in zlib if we can.  This allows us to read and write
-# compressed CTF sections.
+# Link in zlib/zstd if we can.  This allows us to read and write
+# compressed debug sections.
 AM_ZLIB
+AC_ZSTD
 
 # When converting linker scripts into strings for use in emulation
 # files, use astring.sed if the compiler supports ANSI string
diff --git a/ld/emultempl/elf.em b/ld/emultempl/elf.em
index c52484f..acd66f9 100644
--- a/ld/emultempl/elf.em
+++ b/ld/emultempl/elf.em
@@ -668,6 +668,15 @@ gld${EMULATION_NAME}_handle_option (int optc)
 	link_info.compress_debug = COMPRESS_DEBUG_GNU_ZLIB;
       else if (strcasecmp (optarg, "zlib-gabi") == 0)
 	link_info.compress_debug = COMPRESS_DEBUG_GABI_ZLIB;
+      else if (strcasecmp (optarg, "zstd") == 0)
+	{
+#ifdef HAVE_ZSTD
+	  link_info.compress_debug = COMPRESS_DEBUG_ZSTD;
+#else
+	  einfo (_ ("%F%P: --compress-debug-sections=zstd: ld is not built "
+		    "with zstd support\n"));
+#endif
+	}
       else
 	einfo (_("%F%P: invalid --compress-debug-sections option: \`%s'\n"),
 	       optarg);
diff --git a/ld/ld.texi b/ld/ld.texi
index eabbec8..9daed2e 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -2863,10 +2863,12 @@ but for most Linux based systems it will be @code{both}.
 @kindex --compress-debug-sections=zlib
 @kindex --compress-debug-sections=zlib-gnu
 @kindex --compress-debug-sections=zlib-gabi
+@kindex --compress-debug-sections=zstd
 @item --compress-debug-sections=none
 @itemx --compress-debug-sections=zlib
 @itemx --compress-debug-sections=zlib-gnu
 @itemx --compress-debug-sections=zlib-gabi
+@itemx --compress-debug-sections=zstd
 On ELF platforms, these options control how DWARF debug sections are
 compressed using zlib.
 
@@ -2880,6 +2882,9 @@ sets the SHF_COMPRESSED flag in the sections' headers.
 The @option{--compress-debug-sections=zlib} option is an alias for
 @option{--compress-debug-sections=zlib-gabi}.
 
+@option{--compress-debug-sections=zstd} compresses DWARF debug sections using
+zstd.
+
 Note that this option overrides any compression in input debug
 sections, so if a binary is linked with @option{--compress-debug-sections=none}
 for example, then any compressed debug sections in input files will be
diff --git a/ld/ldmain.c b/ld/ldmain.c
index e676c37..d63002c 100644
--- a/ld/ldmain.c
+++ b/ld/ldmain.c
@@ -506,8 +506,12 @@ main (int argc, char **argv)
   if ((link_info.compress_debug & COMPRESS_DEBUG))
     {
       link_info.output_bfd->flags |= BFD_COMPRESS;
-      if (link_info.compress_debug == COMPRESS_DEBUG_GABI_ZLIB)
-	link_info.output_bfd->flags |= BFD_COMPRESS_GABI;
+      if (link_info.compress_debug != COMPRESS_DEBUG_GNU_ZLIB)
+	{
+	  link_info.output_bfd->flags |= BFD_COMPRESS_GABI;
+	  if (link_info.compress_debug == COMPRESS_DEBUG_ZSTD)
+	    link_info.output_bfd->flags |= BFD_COMPRESS_ZSTD;
+	}
     }
 
   ldwrite ();
diff --git a/ld/lexsup.c b/ld/lexsup.c
index 9225f71..299371f 100644
--- a/ld/lexsup.c
+++ b/ld/lexsup.c
@@ -2146,8 +2146,8 @@ elf_static_list_options (FILE *file)
   fprintf (file, _("\
   --package-metadata[=JSON]   Generate package metadata note\n"));
   fprintf (file, _("\
-  --compress-debug-sections=[none|zlib|zlib-gnu|zlib-gabi]\n\
-                              Compress DWARF debug sections using zlib\n"));
+  --compress-debug-sections=[none|zlib|zlib-gnu|zlib-gabi|zstd]\n\
+			      Compress DWARF debug sections\n"));
 #ifdef DEFAULT_FLAG_COMPRESS_DEBUG
   fprintf (file, _("\
                                 Default: zlib-gabi\n"));
diff --git a/ld/testsuite/ld-bootstrap/bootstrap.exp b/ld/testsuite/ld-bootstrap/bootstrap.exp
index 52a91fc..99a1109 100644
--- a/ld/testsuite/ld-bootstrap/bootstrap.exp
+++ b/ld/testsuite/ld-bootstrap/bootstrap.exp
@@ -161,6 +161,10 @@ foreach flags $test_flags {
 	set extralibs "$extralibs -lz"
     }
 
+    if { [lindex [remote_exec build grep "-q \"HAVE_ZSTD 1\" config.h" ] 0] == 0 } then {
+	set extralibs "$extralibs -lzstd"
+    }
+
     # Check if the system's jansson library is used. If so, the object files will
     # be using symbols from it, so link to it.
     if { [lindex [remote_exec build grep "-q \"HAVE_JANSSON 1\" config.h" ] 0] == 0 } then {
diff --git a/ld/testsuite/ld-elf/compress.exp b/ld/testsuite/ld-elf/compress.exp
index cfdd767..28a8486 100644
--- a/ld/testsuite/ld-elf/compress.exp
+++ b/ld/testsuite/ld-elf/compress.exp
@@ -254,3 +254,19 @@ if { [regexp_diff tmpdir/$test.out $srcdir/$subdir/$test.rt] } then {
 } else {
     pass "$test_name"
 }
+
+if { [ld_assemble $as "--compress-debug-sections=zstd $srcdir/$subdir/empty.s" tmpdir/emptyzstd.o ] } {
+    set build_tests {
+      {"Build libzstdfoo.so with zstd compressed debug sections"
+       "-shared" "-fPIC -g -Wa,--compress-debug-sections=zstd -Wl,--compress-debug-sections=zstd"
+       {foo.c} {} "libzstdfoo.so"}
+    }
+    set run_tests {
+	{"Run zstdnormal with libzstdfoo.so with zstd compressed debug sections"
+	 "tmpdir/begin.o tmpdir/libzstdfoo.so tmpdir/end.o -Wl,--compress-debug-sections=zstd" ""
+	 {main.c} "zstdnormal" "normal.out" "-Wa,--compress-debug-sections=zstd"}
+    }
+
+    run_cc_link_tests $build_tests
+    run_ld_link_exec_tests $run_tests
+}