PATCH: PR binutils/13947: Strip applied twice corrupts binaries compiled with --emit-relocs

H.J. Lu hongjiu.lu@intel.com
Thu Apr 12 18:37:00 GMT 2012


Hi,

There is a long standing problem with objcopy/strip where empty reloc
sections are generated. The chain events are

1. copy_section calls _bfd_elf_set_section_contents.
2. _bfd_elf_set_section_contents calls _bfd_elf_compute_section_file_positions.
3. _bfd_elf_compute_section_file_positions calls elf_fake_sections.
4. elf_fake_sections calls _bfd_elf_init_reloc_shdr.
5. _bfd_elf_init_reloc_shdr allocates a new reloc section.

Later, we found out there is no need for relocations.  But it is too
late and we generate empty reloc sections.  This patch adds
copy_relocations_in_section to remove relocations which aren't needed. 
OK to install?

Thanks.


H.J.
---
binutils/

2012-04-12  H.J. Lu  <hongjiu.lu@intel.com>

	PR binutils/13947
	* objcopy.c (copy_object): Call copy_relocations_in_section
	before copy_section.
	(skip_section): New.
	(copy_relocations_in_section): Likewise.
	(copy_section): Use skip_section.  Don't copy relocations here.

binutils/testsuite/

2012-04-12  H.J. Lu  <hongjiu.lu@intel.com>

	PR binutils/13947
	* binutils-all/i386/compressed-1b.d: Remove empty REL section.
	* binutils-all/i386/compressed-1c.d: Likewise.

	* binutils-all/x86-64/compressed-1b.d: Remove empty RELA
	section.
	* binutils-all/x86-64/compressed-1c.d: Likewise.

diff --git a/binutils/objcopy.c b/binutils/objcopy.c
index 230d3e5..d78385f 100644
--- a/binutils/objcopy.c
+++ b/binutils/objcopy.c
@@ -459,6 +459,7 @@ extern bfd_boolean S3Forced;
 /* Forward declarations.  */
 static void setup_section (bfd *, asection *, void *);
 static void setup_bfd_headers (bfd *, bfd *);
+static void copy_relocations_in_section (bfd *, asection *, void *);
 static void copy_section (bfd *, asection *, void *);
 static void get_sections (bfd *, asection *, void *);
 static int compare_section_lma (const void *, const void *);
@@ -1885,6 +1886,9 @@ copy_object (bfd *ibfd, bfd *obfd, const bfd_arch_info_type *input_arch)
 
   bfd_set_symtab (obfd, osympp, symcount);
 
+  /* This has to happen before section positions are set.  */
+  bfd_map_over_sections (ibfd, copy_relocations_in_section, obfd);
+
   /* This has to happen after the symbol table has been set.  */
   bfd_map_over_sections (ibfd, copy_section, obfd);
 
@@ -2588,44 +2592,56 @@ loser:
   bfd_nonfatal_message (NULL, obfd, osection, err);
 }
 
-/* Copy the data of input section ISECTION of IBFD
-   to an output section with the same name in OBFD.
-   If stripping then don't copy any relocation info.  */
+/* Return TRUE if input section ISECTION should be skipped.  */
 
-static void
-copy_section (bfd *ibfd, sec_ptr isection, void *obfdarg)
+static bfd_boolean
+skip_section (bfd *ibfd, sec_ptr isection)
 {
-  bfd *obfd = (bfd *) obfdarg;
-  struct section_list *p;
-  arelent **relpp;
-  long relcount;
   sec_ptr osection;
   bfd_size_type size;
-  long relsize;
   flagword flags;
 
   /* If we have already failed earlier on,
      do not keep on generating complaints now.  */
   if (status != 0)
-    return;
+    return TRUE;
+
+  if (extract_symbol)
+    return TRUE;
 
   if (is_strip_section (ibfd, isection))
-    return;
+    return TRUE;
 
   flags = bfd_get_section_flags (ibfd, isection);
   if ((flags & SEC_GROUP) != 0)
-    return;
+    return TRUE;
 
   osection = isection->output_section;
   size = bfd_get_section_size (isection);
 
   if (size == 0 || osection == 0)
-    return;
+    return TRUE;
 
-  if (extract_symbol)
+  return FALSE;
+}
+
+/* Copy relocations in input section ISECTION of IBFD to an output
+   section with the same name in OBFDARG.  If stripping then don't
+   copy any relocation info.  */
+
+static void
+copy_relocations_in_section (bfd *ibfd, sec_ptr isection, void *obfdarg)
+{
+  bfd *obfd = (bfd *) obfdarg;
+  long relsize;
+  arelent **relpp;
+  long relcount;
+  sec_ptr osection;
+
+  if (skip_section (ibfd, isection))
     return;
 
-  p = find_section_list (bfd_get_section_name (ibfd, isection), FALSE);
+  osection = isection->output_section;
 
   /* Core files do not need to be relocated.  */
   if (bfd_get_format (obfd) == bfd_core)
@@ -2682,8 +2698,32 @@ copy_section (bfd *ibfd, sec_ptr isection, void *obfdarg)
 
       bfd_set_reloc (obfd, osection, relcount == 0 ? NULL : relpp, relcount);
       if (relcount == 0)
-	free (relpp);
+	{
+	  osection->flags &= ~SEC_RELOC;
+	  free (relpp);
+	}
     }
+}
+
+/* Copy the data of input section ISECTION of IBFD
+   to an output section with the same name in OBFD.
+   If stripping then don't copy any relocation info.  */
+
+static void
+copy_section (bfd *ibfd, sec_ptr isection, void *obfdarg)
+{
+  bfd *obfd = (bfd *) obfdarg;
+  struct section_list *p;
+  sec_ptr osection;
+  bfd_size_type size;
+
+  if (skip_section (ibfd, isection))
+    return;
+
+  osection = isection->output_section;
+  size = bfd_get_section_size (isection);
+
+  p = find_section_list (bfd_get_section_name (ibfd, isection), FALSE);
 
   if (bfd_get_section_flags (ibfd, isection) & SEC_HAS_CONTENTS
       && bfd_get_section_flags (obfd, osection) & SEC_HAS_CONTENTS)
diff --git a/binutils/testsuite/binutils-all/i386/compressed-1b.d b/binutils/testsuite/binutils-all/i386/compressed-1b.d
index 1e13f6b..d7ffe21 100644
--- a/binutils/testsuite/binutils-all/i386/compressed-1b.d
+++ b/binutils/testsuite/binutils-all/i386/compressed-1b.d
@@ -5,15 +5,14 @@
 #readelf: -S --wide
 #name: strip on uncompressed debug sections
 
-There are 6 section headers, starting at offset 0x7c:
+There are 5 section headers, starting at offset 0x78:
 
 Section Headers:
   \[Nr\] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
   \[ 0\]                   NULL            00000000 000000 000000 00      0   0  0
   \[ 1\] .text             PROGBITS        00000000 000040 00001b 00  AX  0   0 16
-  \[ 2\] .rel.text         REL             00000000 00016c 000000 08      0   1  4
-  \[ 3\] .data             PROGBITS        00000000 00005c 000000 00  WA  0   0  4
-  \[ 4\] .bss              NOBITS          00000000 00005c 000000 00  WA  0   0  4
-  \[ 5\] .shstrtab         STRTAB          00000000 00005c 000020 00      0   0  1
+  \[ 2\] .data             PROGBITS        00000000 00005c 000000 00  WA  0   0  4
+  \[ 3\] .bss              NOBITS          00000000 00005c 000000 00  WA  0   0  4
+  \[ 4\] .shstrtab         STRTAB          00000000 00005c 00001c 00      0   0  1
 Key to Flags:
 #...
diff --git a/binutils/testsuite/binutils-all/i386/compressed-1c.d b/binutils/testsuite/binutils-all/i386/compressed-1c.d
index 1e7467a..3db18fe 100644
--- a/binutils/testsuite/binutils-all/i386/compressed-1c.d
+++ b/binutils/testsuite/binutils-all/i386/compressed-1c.d
@@ -5,15 +5,14 @@
 #readelf: -S --wide
 #name: strip on compressed debug sections
 
-There are 6 section headers, starting at offset 0x7c:
+There are 5 section headers, starting at offset 0x78:
 
 Section Headers:
   \[Nr\] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
   \[ 0\]                   NULL            00000000 000000 000000 00      0   0  0
   \[ 1\] .text             PROGBITS        00000000 000040 00001b 00  AX  0   0 16
-  \[ 2\] .rel.text         REL             00000000 00016c 000000 08      0   1  4
-  \[ 3\] .data             PROGBITS        00000000 00005c 000000 00  WA  0   0  4
-  \[ 4\] .bss              NOBITS          00000000 00005c 000000 00  WA  0   0  4
-  \[ 5\] .shstrtab         STRTAB          00000000 00005c 000020 00      0   0  1
+  \[ 2\] .data             PROGBITS        00000000 00005c 000000 00  WA  0   0  4
+  \[ 3\] .bss              NOBITS          00000000 00005c 000000 00  WA  0   0  4
+  \[ 4\] .shstrtab         STRTAB          00000000 00005c 00001c 00      0   0  1
 Key to Flags:
 #...
diff --git a/binutils/testsuite/binutils-all/x86-64/compressed-1b.d b/binutils/testsuite/binutils-all/x86-64/compressed-1b.d
index 39a8f59..078ccb6 100644
--- a/binutils/testsuite/binutils-all/x86-64/compressed-1b.d
+++ b/binutils/testsuite/binutils-all/x86-64/compressed-1b.d
@@ -5,15 +5,14 @@
 #readelf: -S --wide
 #name: strip on uncompressed debug sections
 
-There are 6 section headers, starting at offset 0x80:
+There are 5 section headers, starting at offset 0x78:
 
 Section Headers:
   \[Nr\] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
   \[ 0\]                   NULL            0000000000000000 000000 000000 00      0   0  0
   \[ 1\] .text             PROGBITS        0000000000000000 000040 000015 00  AX  0   0 16
-  \[ 2\] .rela.text        RELA            0000000000000000 000200 000000 18      0   1  8
-  \[ 3\] .data             PROGBITS        0000000000000000 000058 000000 00  WA  0   0  4
-  \[ 4\] .bss              NOBITS          0000000000000000 000058 000000 00  WA  0   0  4
-  \[ 5\] .shstrtab         STRTAB          0000000000000000 000058 000021 00      0   0  1
+  \[ 2\] .data             PROGBITS        0000000000000000 000058 000000 00  WA  0   0  4
+  \[ 3\] .bss              NOBITS          0000000000000000 000058 000000 00  WA  0   0  4
+  \[ 4\] .shstrtab         STRTAB          0000000000000000 000058 00001c 00      0   0  1
 Key to Flags:
 #...
diff --git a/binutils/testsuite/binutils-all/x86-64/compressed-1c.d b/binutils/testsuite/binutils-all/x86-64/compressed-1c.d
index 33adfc1..90a3c2d 100644
--- a/binutils/testsuite/binutils-all/x86-64/compressed-1c.d
+++ b/binutils/testsuite/binutils-all/x86-64/compressed-1c.d
@@ -5,15 +5,14 @@
 #readelf: -S --wide
 #name: strip on compressed debug sections
 
-There are 6 section headers, starting at offset 0x80:
+There are 5 section headers, starting at offset 0x78:
 
 Section Headers:
   \[Nr\] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
   \[ 0\]                   NULL            0000000000000000 000000 000000 00      0   0  0
   \[ 1\] .text             PROGBITS        0000000000000000 000040 000015 00  AX  0   0 16
-  \[ 2\] .rela.text        RELA            0000000000000000 000200 000000 18      0   1  8
-  \[ 3\] .data             PROGBITS        0000000000000000 000058 000000 00  WA  0   0  4
-  \[ 4\] .bss              NOBITS          0000000000000000 000058 000000 00  WA  0   0  4
-  \[ 5\] .shstrtab         STRTAB          0000000000000000 000058 000021 00      0   0  1
+  \[ 2\] .data             PROGBITS        0000000000000000 000058 000000 00  WA  0   0  4
+  \[ 3\] .bss              NOBITS          0000000000000000 000058 000000 00  WA  0   0  4
+  \[ 4\] .shstrtab         STRTAB          0000000000000000 000058 00001c 00      0   0  1
 Key to Flags:
 #...



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