Treat a prefix of "$SYSROOT" in the same way as "=" when parsing linker search paths.

PR ld/21251
	* ldfile.c (ldfile_add_library_path): If the path starts with
	$SYSROOT then use the sysroot as the real prefix.
	* ldlang.c (lang_add_input_file): Treat $SYSROOT in the same
	way as =.
	* ldlex.l: Add $SYSROOT as allow prefix for a filename.
	* ld.texinfo (-L): Document that $SYSROOT acts like = when
	prefixing a library search path.
	(INPUT): Likewise.
	* testsuite/ld-scripts/sysroot-prefix.exp: Add $SYSROOT prefix
	tests.

ld/ChangeLog

@@ -1,3 +1,17 @@
+2017-05-18  Nick Clifton  <nickc@redhat.com>
+
+	PR ld/21251
+	* ldfile.c (ldfile_add_library_path): If the path starts with
+	$SYSROOT then use the sysroot as the real prefix.
+	* ldlang.c (lang_add_input_file): Treat $SYSROOT in the same
+	way as =.
+	* ldlex.l: Add $SYSROOT as allow prefix for a filename.
+	* ld.texinfo (-L): Document that $SYSROOT acts like = when
+	prefixing a library search path.
+	(INPUT): Likewise.
+	* testsuite/ld-scripts/sysroot-prefix.exp: Add $SYSROOT prefix
+	tests.
+
 2017-05-18  Alan Modra  <amodra@gmail.com>
 
 	* emultempl/elf32.em: Don't compare boolean values against TRUE or FALSE.

ld/ld.texinfo

@@ -705,9 +705,9 @@ order in which the options appear.  @option{-L} options do not affect
 how @command{ld} searches for a linker script unless @option{-T}
 option is specified.
 
-If @var{searchdir} begins with @code{=}, then the @code{=} will be replaced
+If @var{searchdir} begins with @code{=} or @code{$SYSROOT}, then this
-by the @dfn{sysroot prefix}, controlled by the @samp{--sysroot} option, or
+prefix will be replaced by the @dfn{sysroot prefix}, controlled by the
-specified when the linker is configured.
+@samp{--sysroot} option, or specified when the linker is configured.
 
 @ifset UsesEnvVars
 The default set of paths searched (without being specified with
@@ -3393,8 +3393,9 @@ for in the @dfn{sysroot prefix}.  Otherwise, the linker will try to
 open the file in the current directory.  If it is not found, the
 linker will search through the archive library search path.
 The @dfn{sysroot prefix} can also be forced by specifying @code{=}
-as the first character in the filename path.  See also the
+as the first character in the filename path, or prefixing the filename
-description of @samp{-L} in @ref{Options,,Command Line Options}.
+path with @code{$SYSROOT}.  See also the description of @samp{-L} in
+@ref{Options,,Command Line Options}.
 
 If you use @samp{INPUT (-l@var{file})}, @command{ld} will transform the
 name to @code{lib@var{file}.a}, as with the command line argument

ld/ldfile.c

@@ -112,6 +112,8 @@ ldfile_add_library_path (const char *name, bfd_boolean cmdline)
      now.  */
   if (name[0] == '=')
     new_dirs->name = concat (ld_sysroot, name + 1, (const char *) NULL);
+  else if (CONST_STRNEQ (name, "$SYSROOT"))
+    new_dirs->name = concat (ld_sysroot, name + strlen ("$SYSROOT"), (const char *) NULL);
   else
     new_dirs->name = xstrdup (name);
 }

ld/ldlang.c

@@ -1138,11 +1138,14 @@ lang_add_input_file (const char *name,
 		     lang_input_file_enum_type file_type,
 		     const char *target)
 {
-  if (name != NULL && *name == '=')
+  if (name != NULL
+      && (*name == '=' || CONST_STRNEQ (name, "$SYSROOT")))
     {
       lang_input_statement_type *ret;
       char *sysrooted_name
-	= concat (ld_sysroot, name + 1, (const char *) NULL);
+	= concat (ld_sysroot,
+		  name + (*name == '=' ? 1 : strlen ("$SYSROOT")),
+		  (const char *) NULL);
 
       /* We've now forcibly prepended the sysroot, making the input
 	 file independent of the context.  Therefore, temporarily

ld/ldlex.l

@@ -376,6 +376,11 @@ V_IDENTIFIER [*?.$_a-zA-Z\[\]\-\!\^\\]([*?.$_a-zA-Z0-9\[\]\-\!\^\\]|::)*
 				  return NAME;
 				}
 <INPUTLIST>"="{FILENAMECHAR1}{FILENAMECHAR}*	{
+/* Filename to be prefixed by --sysroot or when non-sysrooted, nothing.  */
+				 yylval.name = xstrdup (yytext);
+				  return NAME;
+				}
+<INPUTLIST>"$SYSROOT"{FILENAMECHAR1}{FILENAMECHAR}*	{
 /* Filename to be prefixed by --sysroot or when non-sysrooted, nothing.  */
 				 yylval.name = xstrdup (yytext);
 				  return NAME;

ld/testsuite/ld-scripts/sysroot-prefix.exp

@@ -76,16 +76,23 @@ set sysroot_prefix_tests {
     {7 "root-anchored but -Lpath" "/sysroot/" {} "cannot find"}
     {7 "full-path" "@cwd@/sysroot/" {} ""}
     {7 "root-anchored =-prefixed -Lpath" "=/sysroot/" {} "cannot find"}
-    {7 "full-path =-prefixed with empty" "=@cwd@/sysroot/" "--sysroot=" ""}
+    {7 "root-anchored $SYSROOT-prefixed -Lpath" "$SYSROOT/sysroot/" {} "cannot find"}
     {7 "plain =-prefixed with empty" "=sysroot/" "--sysroot=" ""}
+    {7 "plain $SYSROOT-prefixed with empty" "$SYSROOTsysroot/" "--sysroot=" ""}
     {6 "root-anchored but script outside sysroot" "/" "--sysroot=@cwd@/sysroot" "cannot find"}
     {6 "root-anchored and script inside sysroot" "/sysroot/" "--sysroot=@cwd@" ""}
     {6 "root-anchored =-prefixed script outside" "=/" "--sysroot=@cwd@/sysroot" ""}
+    {6 "root-anchored $SYSROOT-prefixed script outside" "$SYSROOT/" "--sysroot=@cwd@/sysroot" ""}
     {6 "root-anchored =-prefixed script inside" "=/sysroot/" "--sysroot=@cwd@" ""}
+    {6 "root-anchored $SYSROOT-prefixed script inside" "$SYSROOT/sysroot/" "--sysroot=@cwd@" ""}
     {2 "plain =-prefixed without but -Lpath" "=sysroot/" {} "cannot find"}
+    {2 "plain $SYSROOT-prefixed without but -Lpath" "$SYSROOTsysroot/" {} "cannot find"}
     {2 "full-path =-prefixed without" "=@cwd@/sysroot/" {} "cannot find"}
+    {2 "full-path $SYSROOT-prefixed without" "$SYSROOT@cwd@/sysroot/" {} "cannot find"}
     {1 "plain =-prefixed -Lpath" "=sysroot/" {} ""}
+    {1 "plain $SYSROOT-prefixed -Lpath" "$SYSROOTsysroot/" {} ""}
     {1 "full-path =-prefixed without" "=@cwd@/sysroot/" {} ""}
+    {1 "full-path $SYSROOT-prefixed without" "$SYSROOT@cwd@/sysroot/" {} ""}
 }
 
 # May have to provide a target-specific assembler option for some targets.