ld: Support input section description keyword: REVERSE

PR 27565
  * ldlex.l: Add REVERSE.
  * ldgram.y: Allow REVERSE to be used wherever a sorting command can be used.
  * ld.h (struct wildcard_spec): Add 'reversed' field.
  * ldlang.h (lang_wild_statement_struct): Add 'filenames_reversed' field.
  * ldlang.c (compare_sections): Add reversed parameter. (wild_sort): Reverse the comparison if requested. (print_wild_statement): Handle the reversed field.
  * ld.texi: Document the new feature.
  * NEWS: Mention the new feature.
  * testsuite/ld-scripts/sort-file-reversed-1.d: New test driver.
  * testsuite/ld-scripts/sort-file-reversed-1.t: New test source.
  * testsuite/ld-scripts/sort-file-reversed-2.t: New test source.
  * testsuite/ld-scripts/sort-file-reversed-2.d: New test driver.
  * testsuite/ld-scripts/sort-sections-reversed-1.d: New test driver.
  * testsuite/ld-scripts/sort-sections-reversed-1.t: New test source.
  * testsuite/ld-scripts/sort-sections-reversed-2.t: New test source.
  * testsuite/ld-scripts/sort-sections-reversed-2.d: New test driver.
  * testsuite/ld-scripts/sort-sections-reversed-3.d: New test driver.
  * testsuite/ld-scripts/sort-sections-reversed-3.t: New test source.

ld/ChangeLog

@@ -1,3 +1,27 @@
+2023-11-01  Nick Clifton  <nickc@redhat.com>
+
+	PR 27565
+	* ldlex.l: Add REVERSE.
+	* ldgram.y: Allow REVERSE to be used wherever a sorting command
+	can be used.
+	* ld.h (struct wildcard_spec): Add 'reversed' field.
+	* ldlang.h (lang_wild_statement_struct): Add 'filenames_reversed' field.
+	* ldlang.c (compare_sections): Add reversed parameter.
+	(wild_sort): Reverse the comparison if requested.
+	(print_wild_statement): Handle the reversed field.
+	* ld.texi: Document the new feature.
+	* NEWS: Mention the new feature.
+	* testsuite/ld-scripts/sort-file-reversed-1.d: New test driver.
+	* testsuite/ld-scripts/sort-file-reversed-1.t: New test source.
+	* testsuite/ld-scripts/sort-file-reversed-2.t: New test source.
+	* testsuite/ld-scripts/sort-file-reversed-2.d: New test driver.
+	* testsuite/ld-scripts/sort-sections-reversed-1.d: New test driver.
+	* testsuite/ld-scripts/sort-sections-reversed-1.t: New test source.
+	* testsuite/ld-scripts/sort-sections-reversed-2.t: New test source.
+	* testsuite/ld-scripts/sort-sections-reversed-2.d: New test driver.
+	* testsuite/ld-scripts/sort-sections-reversed-3.d: New test driver.
+	* testsuite/ld-scripts/sort-sections-reversed-3.t: New test source.
+
 2023-10-30  Nick Clifton  <nickc@redhat.com>
 
 	* po/ka.po: New Georgian translation.

ld/NEWS

@@ -12,6 +12,10 @@ Changes in 2.41:
 * The linker command line option --print-map-locals can be used to include
   local symbols in a linker map.  (ELF targets only).
 
+* A new linker script sorting directive has been added: REVERSE.  This reverses
+  the order of the sorting.  It be combined with either SORT_BY_INIT_PRIORITY
+  or SORT_BY_NAME.
+
 * For most ELF based targets, if the --enable-linker-version option is used
   then the version of the linker will be inserted as a string into the .comment
   section.

ld/ld.h

@@ -96,11 +96,14 @@ extern sort_type sort_section;
 
 struct wildcard_spec
 {
-  const char *name;
+  const char *        name;
-  struct name_list *exclude_name_list;
+  struct name_list *  exclude_name_list;
-  struct flag_info *section_flag_list;
+  struct flag_info *  section_flag_list;
-  size_t namelen, prefixlen, suffixlen;
+  size_t              namelen;
-  sort_type sorted;
+  size_t              prefixlen;
+  size_t              suffixlen;
+  sort_type           sorted;
+  bool                reversed;
 };
 
 struct wildcard_list

ld/ld.texi

@@ -5263,6 +5263,35 @@ the init_priority.  In @code{.ctors.NNNNN} and @code{.dtors.NNNNN},
 @cindex SORT
 @code{SORT} is an alias for @code{SORT_BY_NAME}.
 
+@cindex REVERSE
+@code{REVERSE} indicates that the sorting should be reversed.  If used
+on its own then @code{REVERSE} implies @code{SORT_BY_NAME}, otherwise
+it reverses the enclosed @code{SORT..} command.  Note - reverse
+sorting of alignment is not currently supported.
+
+Note - the sorting commands only accept a single wildcard pattern.  So
+for example the following will not work:
+@smallexample
+  *(REVERSE(.text* .init*))
+@end smallexample
+To resolve this problem list the patterns individually, like this:
+@smallexample
+  *(REVERSE(.text*))
+  *(REVERSE(.init*))
+@end smallexample
+
+Note - you can put the @code{EXCLUDE_FILE} command inside a sorting
+command, but not the other way around.  So for example:
+@smallexample
+  *(SORT_BY_NAME(EXCLUDE_FILE(foo) .text*))
+@end smallexample
+will work, but:
+@smallexample
+  *(EXCLUDE_FILE(foo) SORT_BY_NAME(.text*))
+@end smallexample
+will not.
+
+
 When there are nested section sorting commands in linker script, there
 can be at most 1 level of nesting for section sorting commands.
 
@@ -5282,6 +5311,15 @@ treated the same as @code{SORT_BY_NAME} (wildcard section pattern).
 @code{SORT_BY_ALIGNMENT} (@code{SORT_BY_ALIGNMENT} (wildcard section pattern))
 is treated the same as @code{SORT_BY_ALIGNMENT} (wildcard section pattern).
 @item
+@code{SORT_BY_NAME} (@code{REVERSE} (wildcard section pattern))
+reverse sorts by name.
+@item
+@code{REVERSE} (@code{SORT_BY_NAME} (wildcard section pattern))
+reverse sorts by name.
+@item
+@code{SORT_BY_INIT_PRIORITY} (@code{REVERSE} (wildcard section pattern))
+reverse sorts by init priority.
+@item
 All other nested section sorting commands are invalid.
 @end enumerate
 

ld/ldgram.y

@@ -102,7 +102,7 @@ static void yyerror (const char *);
 %type <flag_info> sect_flags
 %type <name> memspec_opt memspec_at_opt paren_script_name casesymlist
 %type <cname> wildcard_name
-%type <wildcard> section_name_spec filename_spec wildcard_maybe_exclude
+%type <wildcard> section_name_spec filename_spec wildcard_maybe_exclude wildcard_maybe_reverse
 %token <bigint> INT
 %token <name> NAME LNAME
 %type <integer> length
@@ -132,7 +132,7 @@ static void yyerror (const char *);
 %token SECTIONS PHDRS INSERT_K AFTER BEFORE LINKER_VERSION
 %token DATA_SEGMENT_ALIGN DATA_SEGMENT_RELRO_END DATA_SEGMENT_END
 %token SORT_BY_NAME SORT_BY_ALIGNMENT SORT_NONE
-%token SORT_BY_INIT_PRIORITY
+%token SORT_BY_INIT_PRIORITY REVERSE
 %token '{' '}'
 %token SIZEOF_HEADERS OUTPUT_FORMAT FORCE_COMMON_ALLOCATION OUTPUT_ARCH
 %token INHIBIT_COMMON_ALLOCATION FORCE_GROUP_ALLOCATION
@@ -440,6 +440,7 @@ wildcard_maybe_exclude:
 			  $$.sorted = none;
 			  $$.exclude_name_list = NULL;
 			  $$.section_flag_list = NULL;
+			  $$.reversed = false;
 			}
 	|	EXCLUDE_FILE '(' exclude_name_list ')' wildcard_name
 			{
@@ -447,65 +448,95 @@ wildcard_maybe_exclude:
 			  $$.sorted = none;
 			  $$.exclude_name_list = $3;
 			  $$.section_flag_list = NULL;
+			  $$.reversed = false;
+			}
+	;
+
+wildcard_maybe_reverse:
+		wildcard_maybe_exclude
+	|	REVERSE '(' wildcard_maybe_exclude ')'
+			{
+			  $$ = $3;
+			  $$.reversed = true;
+			  $$.sorted = by_name;
 			}
 	;
 
 filename_spec:
-		wildcard_maybe_exclude
+		wildcard_maybe_reverse
-	|	SORT_BY_NAME '(' wildcard_maybe_exclude ')'
+	|	SORT_BY_NAME '(' wildcard_maybe_reverse ')'
 			{
 			  $$ = $3;
 			  $$.sorted = by_name;
 			}
-	|	SORT_NONE '(' wildcard_maybe_exclude ')'
+	|	SORT_NONE '(' wildcard_maybe_reverse ')'
 			{
 			  $$ = $3;
 			  $$.sorted = by_none;
+			  $$.reversed = false;
+			}
+	|	REVERSE '(' SORT_BY_NAME '(' wildcard_maybe_exclude ')' ')'
+			{
+			  $$ = $5;
+			  $$.sorted = by_name;
+			  $$.reversed = true;
 			}
 	;
 
 section_name_spec:
-		wildcard_maybe_exclude
+		wildcard_maybe_reverse
-	|	SORT_BY_NAME '(' wildcard_maybe_exclude ')'
+	|	SORT_BY_NAME '(' wildcard_maybe_reverse ')'
 			{
 			  $$ = $3;
 			  $$.sorted = by_name;
 			}
-	|	SORT_BY_ALIGNMENT '(' wildcard_maybe_exclude ')'
+	|	SORT_BY_ALIGNMENT '(' wildcard_maybe_reverse ')'
 			{
 			  $$ = $3;
 			  $$.sorted = by_alignment;
 			}
-	|	SORT_NONE '(' wildcard_maybe_exclude ')'
+	|	SORT_NONE '(' wildcard_maybe_reverse ')'
 			{
 			  $$ = $3;
 			  $$.sorted = by_none;
 			}
-	|	SORT_BY_NAME '(' SORT_BY_ALIGNMENT '(' wildcard_maybe_exclude ')' ')'
+	|	SORT_BY_NAME '(' SORT_BY_ALIGNMENT '(' wildcard_maybe_reverse ')' ')'
 			{
 			  $$ = $5;
 			  $$.sorted = by_name_alignment;
 			}
-	|	SORT_BY_NAME '(' SORT_BY_NAME '(' wildcard_maybe_exclude ')' ')'
+	|	SORT_BY_NAME '(' SORT_BY_NAME '(' wildcard_maybe_reverse ')' ')'
 			{
 			  $$ = $5;
 			  $$.sorted = by_name;
 			}
-	|	SORT_BY_ALIGNMENT '(' SORT_BY_NAME '(' wildcard_maybe_exclude ')' ')'
+	|	SORT_BY_ALIGNMENT '(' SORT_BY_NAME '(' wildcard_maybe_reverse ')' ')'
 			{
 			  $$ = $5;
 			  $$.sorted = by_alignment_name;
 			}
-	|	SORT_BY_ALIGNMENT '(' SORT_BY_ALIGNMENT '(' wildcard_maybe_exclude ')' ')'
+	|	SORT_BY_ALIGNMENT '(' SORT_BY_ALIGNMENT '(' wildcard_maybe_reverse ')' ')'
 			{
 			  $$ = $5;
 			  $$.sorted = by_alignment;
 			}
-	|	SORT_BY_INIT_PRIORITY '(' wildcard_maybe_exclude ')'
+	|	SORT_BY_INIT_PRIORITY '(' wildcard_maybe_reverse ')'
 			{
 			  $$ = $3;
 			  $$.sorted = by_init_priority;
 			}
+	|	REVERSE '(' SORT_BY_NAME '(' wildcard_maybe_exclude ')' ')'
+			{
+			  $$ = $5;
+			  $$.sorted = by_name;
+			  $$.reversed = true;
+			}
+	|	REVERSE '(' SORT_BY_INIT_PRIORITY '(' wildcard_maybe_exclude ')' ')'
+			{
+			  $$ = $5;
+			  $$.sorted = by_init_priority;
+			  $$.reversed = true;
+			}
 	;
 
 sect_flag_list:	NAME

ld/ldlang.c

@@ -539,7 +539,7 @@ get_init_priority (const asection *sec)
 /* Compare sections ASEC and BSEC according to SORT.  */
 
 static int
-compare_section (sort_type sort, asection *asec, asection *bsec)
+compare_section (sort_type sort, asection *asec, asection *bsec, bool reversed)
 {
   int ret;
   int a_priority, b_priority;
@@ -554,7 +554,10 @@ compare_section (sort_type sort, asection *asec, asection *bsec)
       b_priority = get_init_priority (bsec);
       if (a_priority < 0 || b_priority < 0)
 	goto sort_by_name;
-      ret = a_priority - b_priority;
+      if (reversed)
+	ret = b_priority - a_priority;
+      else
+	ret = a_priority - b_priority;
       if (ret)
 	break;
       else
@@ -568,11 +571,17 @@ compare_section (sort_type sort, asection *asec, asection *bsec)
 
     case by_name:
     sort_by_name:
-      ret = strcmp (bfd_section_name (asec), bfd_section_name (bsec));
+      if (reversed)
+	ret = strcmp (bfd_section_name (bsec), bfd_section_name (asec));
+      else
+	ret = strcmp (bfd_section_name (asec), bfd_section_name (bsec));
       break;
 
     case by_name_alignment:
-      ret = strcmp (bfd_section_name (asec), bfd_section_name (bsec));
+      if (reversed)
+	ret = strcmp (bfd_section_name (bsec), bfd_section_name (asec));
+      else
+	ret = strcmp (bfd_section_name (asec), bfd_section_name (bsec));
       if (ret)
 	break;
       /* Fall through.  */
@@ -647,7 +656,11 @@ wild_sort (lang_wild_statement_type *wild,
 	  else
 	    ln = sort_filename (lsec->owner);
 
-	  i = filename_cmp (fn, ln);
+	  if (wild->filenames_reversed)
+	    i = filename_cmp (ln, fn);
+	  else
+	    i = filename_cmp (fn, ln);
+
 	  if (i > 0)
 	    { tree = &((*tree)->right); continue; }
 	  else if (i < 0)
@@ -660,7 +673,11 @@ wild_sort (lang_wild_statement_type *wild,
 	      if (la)
 		ln = sort_filename (lsec->owner);
 
-	      i = filename_cmp (fn, ln);
+	      if (wild->filenames_reversed)
+		i = filename_cmp (ln, fn);
+	      else
+		i = filename_cmp (fn, ln);
+	      
 	      if (i > 0)
 		{ tree = &((*tree)->right); continue; }
 	      else if (i < 0)
@@ -673,7 +690,7 @@ wild_sort (lang_wild_statement_type *wild,
 
       /* Find the correct node to append this section.  */
       if (sec && sec->spec.sorted != none && sec->spec.sorted != by_none
-	  && compare_section (sec->spec.sorted, section, (*tree)->section) < 0)
+	  && compare_section (sec->spec.sorted, section, (*tree)->section, sec->spec.reversed) < 0)
 	tree = &((*tree)->left);
       else
 	tree = &((*tree)->right);
@@ -5151,10 +5168,14 @@ print_wild_statement (lang_wild_statement_type *w,
 
   if (w->filenames_sorted)
     minfo ("SORT_BY_NAME(");
+  if (w->filenames_reversed)
+    minfo ("REVERSE(");
   if (w->filename != NULL)
     minfo ("%s", w->filename);
   else
     minfo ("*");
+  if (w->filenames_reversed)
+    minfo (")");
   if (w->filenames_sorted)
     minfo (")");
 
@@ -5199,6 +5220,12 @@ print_wild_statement (lang_wild_statement_type *w,
 	  break;
 	}
 
+      if (sec->spec.reversed)
+	{
+	  minfo ("REVERSE(");
+	  closing_paren++;
+	}
+
       if (sec->spec.exclude_name_list != NULL)
 	{
 	  name_list *tmp;
@@ -8500,9 +8527,10 @@ lang_add_wild (struct wildcard_spec *filespec,
   if (filespec != NULL)
     {
       new_stmt->filename = filespec->name;
-      new_stmt->filenames_sorted = filespec->sorted == by_name;
+      new_stmt->filenames_sorted = (filespec->sorted == by_name || filespec->reversed);
       new_stmt->section_flag_list = filespec->section_flag_list;
       new_stmt->exclude_name_list = filespec->exclude_name_list;
+      new_stmt->filenames_reversed = filespec->reversed;
     }
   new_stmt->section_list = section_list;
   new_stmt->keep_sections = keep_sections;

ld/ldlang.h

@@ -390,18 +390,19 @@ typedef struct lang_section_bst
 
 struct lang_wild_statement_struct
 {
-  lang_statement_header_type header;
+  lang_statement_header_type  header;
-  const char *filename;
+  lang_statement_list_type    children;
-  bool filenames_sorted;
+  lang_statement_list_type    matching_sections;
-  bool any_specs_sorted;
+  lang_section_bst_type *     tree;
-  struct wildcard_list *section_list;
+  lang_section_bst_type **    rightmost;
-  bool keep_sections;
+  struct wildcard_list *      section_list;
-  lang_statement_list_type children;
+  struct name_list *          exclude_name_list;
-  struct name_list *exclude_name_list;
+  struct flag_info *          section_flag_list;
-  lang_statement_list_type matching_sections;
+  const char *                filename;
-
+  bool                        filenames_sorted;
-  lang_section_bst_type *tree, **rightmost;
+  bool                        filenames_reversed;
-  struct flag_info *section_flag_list;
+  bool                        any_specs_sorted;
+  bool                        keep_sections;
 };
 
 typedef struct lang_address_statement_struct

ld/ldlex.l

@@ -322,6 +322,7 @@ V_IDENTIFIER [*?.$_a-zA-Z\[\]\-\!\^\\]([*?.$_a-zA-Z0-9\[\]\-\!\^\\]|::)*
 <WILD>"SORT"				{ RTOKEN(SORT_BY_NAME); }
 <WILD>"SORT_BY_INIT_PRIORITY"		{ RTOKEN(SORT_BY_INIT_PRIORITY); }
 <WILD>"SORT_NONE"			{ RTOKEN(SORT_NONE); }
+<WILD>"REVERSE"				{ RTOKEN(REVERSE); }
 <EXPRESSION>"NOLOAD"			{ RTOKEN(NOLOAD); }
 <EXPRESSION>"READONLY"			{ RTOKEN(READONLY); }
 <EXPRESSION>"DSECT"			{ RTOKEN(DSECT); }

ld/testsuite/ld-scripts/sort-file-reversed-1.d

@@ -0,0 +1,18 @@
+#source: sort-file1.s
+#source: sort-file2.s
+#ld: -T sort-file-reversed-1.t --no-warn-rwx-segments
+#nm: -n
+
+# Check that SORT_BY_NAME+REVERSE on filenames works.
+# The text sections should come in reversed sorted order, the data
+# sections in input order.  Note how we specifically pass
+# the object filenames in alphabetical order
+#...
+0[0-9a-f]* t infile2
+#...
+0[0-9a-f]* t infile1
+#...
+0[0-9a-f]* d data1
+#...
+0[0-9a-f]* d data2
+#pass

ld/testsuite/ld-scripts/sort-file-reversed-1.t

@@ -0,0 +1,6 @@
+SECTIONS
+{
+  .text : { SORT_BY_NAME(REVERSE(*))(.text*) }
+  .data : { *(.data*) }
+  /DISCARD/ : { *(.*) }
+}

ld/testsuite/ld-scripts/sort-file-reversed-2.d

@@ -0,0 +1,19 @@
+#source: sort-file1.s
+#source: sort-file2.s
+#ld: -T sort-file-reversed-2.t  --no-warn-rwx-segments
+#nm: -n
+
+# Check that REVERSE+SORT_BY_NAME on filenames works.
+# Also check that REVERSE implies SORT_BY_NAME.
+# The text sections should come in reversed sorted order, the data
+# sections in reversed order too.  Note how we specifically pass
+# the object filenames in alphabetical order
+#...
+0[0-9a-f]* t infile2
+#...
+0[0-9a-f]* t infile1
+#...
+0[0-9a-f]* d data2
+#...
+0[0-9a-f]* d data1
+#pass

ld/testsuite/ld-scripts/sort-file-reversed-2.t

@@ -0,0 +1,6 @@
+SECTIONS
+{
+  .text : { REVERSE(SORT_BY_NAME(*))(.text*) }
+  .data : { REVERSE(*)(.data*) }
+  /DISCARD/ : { *(.*) }
+}

ld/testsuite/ld-scripts/sort-sections-reversed-1.d

@@ -0,0 +1,13 @@
+#source: sort_b_a.s
+#ld: -T sort-sections-reversed-1.t  --no-warn-rwx-segments
+#nm: -n
+
+#...
+0[0-9a-f]* t text3
+#...
+0[0-9a-f]* t text2
+#...
+0[0-9a-f]* t text1
+#...
+0[0-9a-f]* t text
+#pass

ld/testsuite/ld-scripts/sort-sections-reversed-1.t

@@ -0,0 +1,5 @@
+SECTIONS
+{
+  .text : { *(SORT_BY_NAME(REVERSE(.text*))) }
+  /DISCARD/ : { *(.*) }
+}

ld/testsuite/ld-scripts/sort-sections-reversed-2.d

@@ -0,0 +1,13 @@
+#source: sort_b_a.s
+#ld: -T sort-sections-reversed-2.t  --no-warn-rwx-segments
+#nm: -n
+
+#...
+0[0-9a-f]* t text3
+#...
+0[0-9a-f]* t text2
+#...
+0[0-9a-f]* t text1
+#...
+0[0-9a-f]* t text
+#pass

ld/testsuite/ld-scripts/sort-sections-reversed-2.t

@@ -0,0 +1,5 @@
+SECTIONS
+{
+  .text : { *(REVERSE(SORT_BY_INIT_PRIORITY(.text*))) }
+  /DISCARD/ : { *(REVERSE(.*)) }
+}

ld/testsuite/ld-scripts/sort-sections-reversed-3.d

@@ -0,0 +1,15 @@
+#source: sort_b_a.s
+#ld: -T sort-sections-reversed-3.t  --no-warn-rwx-segments
+#nm: -n
+
+# Check that REVERSE implies SORT_BY_NAME for sections.
+# Also check that EXCLUDE_FILE() is supported inside REVERSE.
+#...
+0[0-9a-f]* t text3
+#...
+0[0-9a-f]* t text2
+#...
+0[0-9a-f]* t text1
+#...
+0[0-9a-f]* t text
+#pass

ld/testsuite/ld-scripts/sort-sections-reversed-3.t

@@ -0,0 +1,5 @@
+SECTIONS
+{
+  .text : { *(REVERSE(EXCLUDE_FILE(foo) .text*)) }
+  /DISCARD/ : { *(.*) }
+}