strip: Deal with ARM data marker symbols pointing to debug sections.

ARM data marker symbols "$d" indicate the start of a sequence of data
items in a section. For data only sections no data marker symbol is
necessary, but may be put pointing to the start of the section.
binutils however has a bug which places a data marker symbol somewhere
inside the section (at least for .debug_frame).
https://sourceware.org/bugzilla/show_bug.cgi?id=21809

When strip finds a symbol pointing to a debug section that would be
put into the .debug file then it will copy over the whole symbol table.
This isn't necessary because the symbol is redundant.

Add an ebl hook to recognize data marker symbols with implementations
for arm and aarch64. Use it in strip to strip such symbols from the
symbol table if they point to a debug section.

Signed-off-by: Mark Wielaard <[email protected]>

1 files changed, 24 insertions, 6 deletions

diff --git a/src/strip.c b/src/strip.c
index 4a35ea1d..773ed548 100644
--- a/src/strip.c
+++ b/src/strip.c
@@ -1,5 +1,5 @@
 /* Discard section not used at runtime from object files.
-   Copyright (C) 2000-2012, 2014, 2015, 2016 Red Hat, Inc.
+   Copyright (C) 2000-2012, 2014, 2015, 2016, 2017 Red Hat, Inc.
    This file is part of elfutils.
    Written by Ulrich Drepper <[email protected]>, 2000.
 
@@ -960,8 +960,19 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
 		      if (shdr_info[scnidx].idx == 0)
 			/* This symbol table has a real symbol in
 			   a discarded section.  So preserve the
-			   original table in the debug file.  */
-			shdr_info[cnt].debug_data = symdata;
+			   original table in the debug file.  Unless
+			   it is a redundant data marker to a debug
+			   (data only) section.  */
+			if (! (ebl_section_strip_p (ebl, ehdr,
+						    &shdr_info[scnidx].shdr,
+						    shdr_info[scnidx].name,
+						    remove_comment,
+						    remove_debug)
+			       && ebl_data_marker_symbol (ebl, sym,
+					elf_strptr (elf,
+						    shdr_info[cnt].shdr.sh_link,
+						    sym->st_name))))
+			  shdr_info[cnt].debug_data = symdata;
 		    }
 		}
 
@@ -1293,7 +1304,10 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
 	shdr_info[cnt].shdr.sh_name = dwelf_strent_off (shdr_info[cnt].se);
 
 	/* Update the section header from the input file.  Some fields
-	   might be section indeces which now have to be adjusted.  */
+	   might be section indeces which now have to be adjusted.  Keep
+	   the index to the "current" sh_link in case we need it to lookup
+	   symbol table names.  */
+	size_t sh_link = shdr_info[cnt].shdr.sh_link;
 	if (shdr_info[cnt].shdr.sh_link != 0)
 	  shdr_info[cnt].shdr.sh_link =
 	    shdr_info[shdr_info[cnt].shdr.sh_link].idx;
@@ -1492,13 +1506,17 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
 		      /* The symbol points to a section that is discarded
 			 but isn't preserved in the debug file. Check that
 			 this is a section or group signature symbol
-			 for a section which has been removed.  */
+			 for a section which has been removed.  Or a special
+			 data marker symbol to a debug section.  */
 		      {
 			elf_assert (GELF_ST_TYPE (sym->st_info) == STT_SECTION
 				    || ((shdr_info[sidx].shdr.sh_type
 					 == SHT_GROUP)
 					&& (shdr_info[sidx].shdr.sh_info
-					    == inner)));
+					    == inner))
+				    || ebl_data_marker_symbol (ebl, sym,
+						elf_strptr (elf, sh_link,
+							    sym->st_name)));
 		      }
 		  }