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[PATCH] ld: Add support for a new option, -exclude-symbols, in COFF object file directives

Martin Storsjo martin@martin.st
Tue Jul 19 20:33:30 GMT 2022 
This maps to the same as ld's --exclude-symbols command line option,
but allowing specifying the option via directives embedded in the
object files instead of passed manually on the command line.
---
I've posted a corresponding patch to LLD in
https://reviews.llvm.org/D130120 - I'd like to have support for it
in both linkers before I'd take the option into use.
---
 ld/deffile.h  |  6 ++++++
 ld/deffilep.y | 43 ++++++++++++++++++++++++++++++++++++++++++-
 ld/pe-dll.c   | 10 ++++++++++
 3 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/ld/deffile.h b/ld/deffile.h
index d68fa8c6ba1..306ae3a6f75 100644
--- a/ld/deffile.h
+++ b/ld/deffile.h
@@ -61,6 +61,11 @@ typedef struct def_file_aligncomm {
   unsigned int alignment;	/* log-2 alignment.        */
 } def_file_aligncomm;
 
+typedef struct def_file_exclude_symbol {
+  struct def_file_exclude_symbol *next;	/* Chain pointer.  */
+  char *symbol_name;		/* Name of excluded symbol.  */
+} def_file_exclude_symbol;
+
 typedef struct def_file {
   /* From the NAME or LIBRARY command.  */
   char *name;
@@ -94,6 +99,7 @@ typedef struct def_file {
 
   /* Only expected from .drectve sections, not .DEF files.  */
   def_file_aligncomm *aligncomms;
+  def_file_exclude_symbol *exclude_symbols;
 
 } def_file;
 
diff --git a/ld/deffilep.y b/ld/deffilep.y
index 3f610ddbe14..a7db23eace6 100644
--- a/ld/deffilep.y
+++ b/ld/deffilep.y
@@ -101,6 +101,7 @@ static void def_stacksize (int, int);
 static void def_version (int, int);
 static void def_directive (char *);
 static void def_aligncomm (char *str, int align);
+static void def_exclude_symbols (char *str);
 static int def_parse (void);
 static void def_error (const char *);
 static int def_lex (void);
@@ -121,7 +122,7 @@ static const char *lex_parse_string_end = 0;
 
 %token NAME LIBRARY DESCRIPTION STACKSIZE_K HEAPSIZE CODE DATAU DATAL
 %token SECTIONS EXPORTS IMPORTS VERSIONK BASE CONSTANTU CONSTANTL
-%token PRIVATEU PRIVATEL ALIGNCOMM
+%token PRIVATEU PRIVATEL ALIGNCOMM EXCLUDE_SYMBOLS
 %token READ WRITE EXECUTE SHARED_K NONAMEU NONAMEL DIRECTIVE EQUAL
 %token <id> ID
 %token <digits> DIGITS
@@ -155,6 +156,7 @@ command:
 	|	VERSIONK NUMBER '.' NUMBER { def_version ($2, $4);}
 	|	DIRECTIVE ID { def_directive ($2);}
 	|	ALIGNCOMM anylang_id ',' NUMBER { def_aligncomm ($2, $4);}
+	|	EXCLUDE_SYMBOLS anylang_id { def_exclude_symbols ($2);}
 	;
 
 
@@ -488,6 +490,15 @@ def_file_free (def_file *fdef)
       free (c);
     }
 
+  while (fdef->exclude_symbols)
+    {
+      def_file_exclude_symbol *e = fdef->exclude_symbols;
+
+      fdef->exclude_symbols = fdef->exclude_symbols->next;
+      free (e->symbol_name);
+      free (e);
+    }
+
   free (fdef);
 }
 
@@ -946,6 +957,7 @@ diropts[] =
   { "-attr", SECTIONS },
   { "-export", EXPORTS },
   { "-aligncomm", ALIGNCOMM },
+  { "-exclude-symbols", EXCLUDE_SYMBOLS },
   { 0, 0 }
 };
 
@@ -1261,6 +1273,35 @@ def_aligncomm (char *str, int align)
     }
 }
 
+static void
+def_exclude_symbols (char *str)
+{
+  def_file_exclude_symbol *c, *p;
+
+  p = NULL;
+  c = def->exclude_symbols;
+  while (c != NULL)
+    {
+      int e = strcmp (c->symbol_name, str);
+      if (!e)
+        return;
+      c = (p = c)->next;
+    }
+
+  c = xmalloc (sizeof (def_file_exclude_symbol));
+  c->symbol_name = xstrdup (str);
+  if (!p)
+    {
+      c->next = def->exclude_symbols;
+      def->exclude_symbols = c;
+    }
+  else
+    {
+      c->next = p->next;
+      p->next = c;
+    }
+}
+
 static void
 def_error (const char *err)
 {
diff --git a/ld/pe-dll.c b/ld/pe-dll.c
index db2c75da9b5..33be53d6164 100644
--- a/ld/pe-dll.c
+++ b/ld/pe-dll.c
@@ -718,6 +718,16 @@ process_def_file_and_drectve (bfd *abfd ATTRIBUTE_UNUSED, struct bfd_link_info *
 	}
     }
 
+  if (pe_def_file->exclude_symbols)
+    {
+      def_file_exclude_symbol *ac = pe_def_file->exclude_symbols;
+      while (ac)
+	{
+	  pe_dll_add_excludes (ac->symbol_name, EXCLUDESYMS);
+	  ac = ac->next;
+	}
+    }
+
   /* If we are building an executable and there is nothing
      to export, we do not build an export table at all.  */
   if (bfd_link_executable (info) && pe_def_file->num_exports == 0
-- 
2.25.1
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