From 76b336e1655c8eacaf17a362c3c59d6103357c09 Mon Sep 17 00:00:00 2001

From: Alan Modra <amodra@gmail.com>

Date: Sun, 8 Nov 2015 09:29:00 -0800

Subject: [PATCH 09/11] ELF unexec: Don't insert a new section

Reuse the .bss section instead, making it SHT_PROGBITS.  This way we

don't need to mess with symbol st_shndx, or section sh_link and

sh_info.

This does lead to eu-elflint complaints about symbols defined in .bss

with a needed version, because normally it is undefined symbols that

have needed versions;  Defined symbols have version definitions.

The exception is symbols defined by the linker in .dynbss for

variables copied from a shared library in order to avoid text

relocations, with copy relocs to copy their initial values from the

shared library.  These symbols are both defined and have needed

versions, and eu-elflink only expects to see them in SHT_NOBITS

sections.  Of course there is no real problem with having such symbols

in SHT_PROGBITS sections.  glibc ld.so handles them fine.

* unexelf.c: Delete outdated comments.

(PATCH_INDEX): Delete.

(find_section): Delete.

(unexec): Don't add a new section.  Instead reuse the last bss

section, extending it to cover dumped data.  Make bss sections

SHT_PROGBITS.  Remove all patching of sh_link, sh_info and

st_shndx.  Rename bss sections.

---

 src/unexelf.c | 524 ++++++----------------------------------------------------

 1 file changed, 50 insertions(+), 474 deletions(-)

diff --git a/src/unexelf.c b/src/unexelf.c

index 4e9c50d..85ed934 100644

--- a/src/unexelf.c

+++ b/src/unexelf.c

@@ -40,347 +40,6 @@ what you give them.   Help stamp out software-hoarding!  */

  * On some machines, an existing old_name file is required.

  *

  */

-

-/* Even more heavily modified by james@bigtex.cactus.org of Dell Computer Co.

- * ELF support added.

- *

- * Basic theory: the data space of the running process needs to be

- * dumped to the output file.  Normally we would just enlarge the size

- * of .data, scooting everything down.  But we can't do that in ELF,

- * because there is often something between the .data space and the

- * .bss space.

- *

- * In the temacs dump below, notice that the Global Offset Table

- * (.got) and the Dynamic link data (.dynamic) come between .data1 and

- * .bss.  It does not work to overlap .data with these fields.

- *

- * The solution is to create a new .data segment.  This segment is

- * filled with data from the current process.  Since the contents of

- * various sections refer to sections by index, the new .data segment

- * is made the last in the table to avoid changing any existing index.

-

- * This is an example of how the section headers are changed.  "Addr"

- * is a process virtual address.  "Offset" is a file offset.

-

-raid:/nfs/raid/src/dist-18.56/src> dump -h temacs

-

-temacs:

-

-           **** SECTION HEADER TABLE ****

- [No]    Type    Flags   Addr         Offset       Size          Name

-         Link    Info    Adralgn      Entsize

-

- [1]     1       2       0x80480d4    0xd4         0x13          .interp

-         0       0       0x1          0

-

- [2]     5       2       0x80480e8    0xe8         0x388         .hash

-         3       0       0x4          0x4

-

- [3]     11      2       0x8048470    0x470        0x7f0         .dynsym

-         4       1       0x4          0x10

-

- [4]     3       2       0x8048c60    0xc60        0x3ad         .dynstr

-         0       0       0x1          0

-

- [5]     9       2       0x8049010    0x1010       0x338         .rel.plt

-         3       7       0x4          0x8

-

- [6]     1       6       0x8049348    0x1348       0x3           .init

-         0       0       0x4          0

-

- [7]     1       6       0x804934c    0x134c       0x680         .plt

-         0       0       0x4          0x4

-

- [8]     1       6       0x80499cc    0x19cc       0x3c56f       .text

-         0       0       0x4          0

-

- [9]     1       6       0x8085f3c    0x3df3c      0x3           .fini

-         0       0       0x4          0

-

- [10]    1       2       0x8085f40    0x3df40      0x69c         .rodata

-         0       0       0x4          0

-

- [11]    1       2       0x80865dc    0x3e5dc      0xd51         .rodata1

-         0       0       0x4          0

-

- [12]    1       3       0x8088330    0x3f330      0x20afc       .data

-         0       0       0x4          0

-

- [13]    1       3       0x80a8e2c    0x5fe2c      0x89d         .data1

-         0       0       0x4          0

-

- [14]    1       3       0x80a96cc    0x606cc      0x1a8         .got

-         0       0       0x4          0x4

-

- [15]    6       3       0x80a9874    0x60874      0x80          .dynamic

-         4       0       0x4          0x8

-

- [16]    8       3       0x80a98f4    0x608f4      0x449c        .bss

-         0       0       0x4          0

-

- [17]    2       0       0            0x608f4      0x9b90        .symtab

-         18      371     0x4          0x10

-

- [18]    3       0       0            0x6a484      0x8526        .strtab

-         0       0       0x1          0

-

- [19]    3       0       0            0x729aa      0x93          .shstrtab

-         0       0       0x1          0

-

- [20]    1       0       0            0x72a3d      0x68b7        .comment

-         0       0       0x1          0

-

- raid:/nfs/raid/src/dist-18.56/src> dump -h xemacs

-

- xemacs:

-

-            **** SECTION HEADER TABLE ****

- [No]    Type    Flags   Addr         Offset       Size          Name

-         Link    Info    Adralgn      Entsize

-

- [1]     1       2       0x80480d4    0xd4         0x13          .interp

-         0       0       0x1          0

-

- [2]     5       2       0x80480e8    0xe8         0x388         .hash

-         3       0       0x4          0x4

-

- [3]     11      2       0x8048470    0x470        0x7f0         .dynsym

-         4       1       0x4          0x10

-

- [4]     3       2       0x8048c60    0xc60        0x3ad         .dynstr

-         0       0       0x1          0

-

- [5]     9       2       0x8049010    0x1010       0x338         .rel.plt

-         3       7       0x4          0x8

-

- [6]     1       6       0x8049348    0x1348       0x3           .init

-         0       0       0x4          0

-

- [7]     1       6       0x804934c    0x134c       0x680         .plt

-         0       0       0x4          0x4

-

- [8]     1       6       0x80499cc    0x19cc       0x3c56f       .text

-         0       0       0x4          0

-

- [9]     1       6       0x8085f3c    0x3df3c      0x3           .fini

-         0       0       0x4          0

-

- [10]    1       2       0x8085f40    0x3df40      0x69c         .rodata

-         0       0       0x4          0

-

- [11]    1       2       0x80865dc    0x3e5dc      0xd51         .rodata1

-         0       0       0x4          0

-

- [12]    1       3       0x8088330    0x3f330      0x20afc       .data

-         0       0       0x4          0

-

- [13]    1       3       0x80a8e2c    0x5fe2c      0x89d         .data1

-         0       0       0x4          0

-

- [14]    1       3       0x80a96cc    0x606cc      0x1a8         .got

-         0       0       0x4          0x4

-

- [15]    6       3       0x80a9874    0x60874      0x80          .dynamic

-         4       0       0x4          0x8

-

- [16]    8       3       0x80c6800    0x7d800      0             .bss

-         0       0       0x4          0

-

- [17]    2       0       0            0x7d800      0x9b90        .symtab

-         18      371     0x4          0x10

-

- [18]    3       0       0            0x87390      0x8526        .strtab

-         0       0       0x1          0

-

- [19]    3       0       0            0x8f8b6      0x93          .shstrtab

-         0       0       0x1          0

-

- [20]    1       0       0            0x8f949      0x68b7        .comment

-         0       0       0x1          0

-

- [21]    1       3       0x80a98f4    0x608f4      0x1cf0c       .data

-         0       0       0x4          0

-

-  * This is an example of how the file header is changed.  "Shoff" is

-  * the section header offset within the file.  Since that table is

-  * after the new .data section, it is moved.  "Shnum" is the number of

-  * sections, which we increment.

-  *

-  * "Phoff" is the file offset to the program header.  "Phentsize" and

-  * "Shentsz" are the program and section header entries sizes respectively.

-  * These can be larger than the apparent struct sizes.

-

- raid:/nfs/raid/src/dist-18.56/src> dump -f temacs

-

- temacs:

-

-                     **** ELF HEADER ****

- Class        Data       Type         Machine     Version

- Entry        Phoff      Shoff        Flags       Ehsize

- Phentsize    Phnum      Shentsz      Shnum       Shstrndx

-

- 1            1          2            3           1

- 0x80499cc    0x34       0x792f4      0           0x34

- 0x20         5          0x28         21          19

-

- raid:/nfs/raid/src/dist-18.56/src> dump -f xemacs

-

- xemacs:

-

-                     **** ELF HEADER ****

- Class        Data       Type         Machine     Version

- Entry        Phoff      Shoff        Flags       Ehsize

- Phentsize    Phnum      Shentsz      Shnum       Shstrndx

-

- 1            1          2            3           1

- 0x80499cc    0x34       0x96200      0           0x34

- 0x20         5          0x28         22          19

-

-  * These are the program headers.  "Offset" is the file offset to the

-  * segment.  "Vaddr" is the memory load address.  "Filesz" is the

-  * segment size as it appears in the file, and "Memsz" is the size in

-  * memory.  Below, the third segment is the code and the fourth is the

-  * data: the difference between Filesz and Memsz is .bss

-

- raid:/nfs/raid/src/dist-18.56/src> dump -o temacs

-

- temacs:

-  ***** PROGRAM EXECUTION HEADER *****

- Type        Offset      Vaddr       Paddr

- Filesz      Memsz       Flags       Align

-

- 6           0x34        0x8048034   0

- 0xa0        0xa0        5           0

-

- 3           0xd4        0           0

- 0x13        0           4           0

-

- 1           0x34        0x8048034   0

- 0x3f2f9     0x3f2f9     5           0x1000

-

- 1           0x3f330     0x8088330   0

- 0x215c4     0x25a60     7           0x1000

-

- 2           0x60874     0x80a9874   0

- 0x80        0           7           0

-

- raid:/nfs/raid/src/dist-18.56/src> dump -o xemacs

-

- xemacs:

-  ***** PROGRAM EXECUTION HEADER *****

- Type        Offset      Vaddr       Paddr

- Filesz      Memsz       Flags       Align

-

- 6           0x34        0x8048034   0

- 0xa0        0xa0        5           0

-

- 3           0xd4        0           0

- 0x13        0           4           0

-

- 1           0x34        0x8048034   0

- 0x3f2f9     0x3f2f9     5           0x1000

-

- 1           0x3f330     0x8088330   0

- 0x3e4d0     0x3e4d0     7           0x1000

-

- 2           0x60874     0x80a9874   0

- 0x80        0           7           0

-

-

- */

-

-/* Modified by wtien@urbana.mcd.mot.com of Motorola Inc.

- *

- * The above mechanism does not work if the unexeced ELF file is being

- * re-layout by other applications (such as `strip'). All the applications

- * that re-layout the internal of ELF will layout all sections in ascending

- * order of their file offsets. After the re-layout, the data2 section will

- * still be the LAST section in the section header vector, but its file offset

- * is now being pushed far away down, and causes part of it not to be mapped

- * in (ie. not covered by the load segment entry in PHDR vector), therefore

- * causes the new binary to fail.

- *

- * The solution is to modify the unexec algorithm to insert the new data2

- * section header right before the new bss section header, so their file

- * offsets will be in the ascending order. Since some of the section's (all

- * sections AFTER the bss section) indexes are now changed, we also need to

- * modify some fields to make them point to the right sections. This is done

- * by macro PATCH_INDEX. All the fields that need to be patched are:

- *

- * 1. ELF header e_shstrndx field.

- * 2. section header sh_link and sh_info field.

- * 3. symbol table entry st_shndx field.

- *

- * The above example now should look like:

-

-           **** SECTION HEADER TABLE ****

- [No]    Type    Flags   Addr         Offset       Size          Name

-         Link    Info    Adralgn      Entsize

-

- [1]     1       2       0x80480d4    0xd4         0x13          .interp

-         0       0       0x1          0

-

- [2]     5       2       0x80480e8    0xe8         0x388         .hash

-         3       0       0x4          0x4

-

- [3]     11      2       0x8048470    0x470        0x7f0         .dynsym

-         4       1       0x4          0x10

-

- [4]     3       2       0x8048c60    0xc60        0x3ad         .dynstr

-         0       0       0x1          0

-

- [5]     9       2       0x8049010    0x1010       0x338         .rel.plt

-         3       7       0x4          0x8

-

- [6]     1       6       0x8049348    0x1348       0x3           .init

-         0       0       0x4          0

-

- [7]     1       6       0x804934c    0x134c       0x680         .plt

-         0       0       0x4          0x4

-

- [8]     1       6       0x80499cc    0x19cc       0x3c56f       .text

-         0       0       0x4          0

-

- [9]     1       6       0x8085f3c    0x3df3c      0x3           .fini

-         0       0       0x4          0

-

- [10]    1       2       0x8085f40    0x3df40      0x69c         .rodata

-         0       0       0x4          0

-

- [11]    1       2       0x80865dc    0x3e5dc      0xd51         .rodata1

-         0       0       0x4          0

-

- [12]    1       3       0x8088330    0x3f330      0x20afc       .data

-         0       0       0x4          0

-

- [13]    1       3       0x80a8e2c    0x5fe2c      0x89d         .data1

-         0       0       0x4          0

-

- [14]    1       3       0x80a96cc    0x606cc      0x1a8         .got

-         0       0       0x4          0x4

-

- [15]    6       3       0x80a9874    0x60874      0x80          .dynamic

-         4       0       0x4          0x8

-

- [16]    1       3       0x80a98f4    0x608f4      0x1cf0c       .data

-         0       0       0x4          0

-

- [17]    8       3       0x80c6800    0x7d800      0             .bss

-         0       0       0x4          0

-

- [18]    2       0       0            0x7d800      0x9b90        .symtab

-         19      371     0x4          0x10

-

- [19]    3       0       0            0x87390      0x8526        .strtab

-         0       0       0x1          0

-

- [20]    3       0       0            0x8f8b6      0x93          .shstrtab

-         0       0       0x1          0

-

- [21]    1       0       0            0x8f949      0x68b7        .comment

-         0       0       0x1          0

-

- */

 /* We do not use mmap because that fails with NFS.

    Instead we read the whole file, modify it, and write it out.  */

@@ -552,45 +211,15 @@ entry_address (void *section_h, ptrdiff_t idx, ptrdiff_t entsize)

 #define NEW_PROGRAM_H(n) \

   (*(ElfW (Phdr) *) entry_address (new_program_h, n, new_file_h->e_phentsize))

-#define PATCH_INDEX(n) ((n) += old_bss_index <= (n))

 typedef unsigned char byte;

-/* Return the index of the section named NAME.

-   SECTION_NAMES, FILE_NAME and FILE_H give information

-   about the file we are looking in.

-

-   If we don't find the section NAME, that is a fatal error

-   if NOERROR is false; return -1 if NOERROR is true.  */

-

-static ptrdiff_t

-find_section (const char *name, const char *section_names, const char *file_name,

-	      ElfW (Ehdr) *old_file_h, ElfW (Shdr) *old_section_h,

-	      bool noerror)

-{

-  ptrdiff_t idx;

-

-  for (idx = 1; idx < old_file_h->e_shnum; idx++)

-    {

-      char const *found_name = section_names + OLD_SECTION_H (idx).sh_name;

-#ifdef UNEXELF_DEBUG

-      fprintf (stderr, "Looking for %s - found %s\n", name, found_name);

-#endif

-      if (strcmp (name, found_name) == 0)

-	return idx;

-    }

-

-  if (! noerror)

-    fatal ("Can't find %s in %s", name, file_name);

-  return -1;

-}

-

 /* ****************************************************************

  * unexec

  *

  * driving logic.

  *

- * In ELF, this works by replacing the old .bss section with a new

- * .data section, and inserting an empty .bss immediately afterwards.

+ * In ELF, this works by replacing the old bss SHT_NOBITS section with

+ * a new, larger, SHT_PROGBITS section.

  *

  */

 void

@@ -615,18 +244,16 @@ unexec (const char *new_name, const char *old_name)

   ElfW (Phdr) *old_program_h, *new_program_h;

   ElfW (Shdr) *old_section_h, *new_section_h;

-  /* Point to the section name table in the old file.  */

-  char *old_section_names;

+  /* Point to the section name table.  */

+  char *old_section_names, *new_section_names;

   ElfW (Phdr) *old_bss_seg, *new_bss_seg;

   ElfW (Addr) old_bss_addr, new_bss_addr;

   ElfW (Word) old_bss_size, new_data2_size;

-  ElfW (Off)  new_data2_offset;

-  ElfW (Addr) new_data2_addr;

-  ElfW (Off)  old_bss_offset;

+  ElfW (Off)  old_bss_offset, new_data2_offset;

-  ptrdiff_t n, nn;

-  ptrdiff_t old_bss_index, old_data_index;

+  ptrdiff_t n;

+  ptrdiff_t old_bss_index;

   struct stat stat_buf;

   off_t old_file_size;

@@ -688,7 +315,7 @@ unexec (const char *new_name, const char *old_name)

   old_bss_offset = old_bss_seg->p_offset + old_bss_seg->p_filesz;

   old_bss_size = old_bss_seg->p_memsz - old_bss_seg->p_filesz;

-  /* Find the first bss style section in the bss segment range.  */

+  /* Find the last bss style section in the bss segment range.  */

   old_bss_index = -1;

   for (n = old_file_h->e_shnum; --n > 0; )

     {

@@ -697,22 +324,15 @@ unexec (const char *new_name, const char *old_name)

 	  && shdr->sh_addr >= old_bss_addr

 	  && shdr->sh_addr + shdr->sh_size <= old_bss_addr + old_bss_size

 	  && (old_bss_index == -1

-	      || OLD_SECTION_H (old_bss_index).sh_addr > shdr->sh_addr))

+	      || OLD_SECTION_H (old_bss_index).sh_addr < shdr->sh_addr))

 	old_bss_index = n;

     }

   if (old_bss_index == -1)

     fatal ("no bss section found");

-  /* Find the old .data section.  Figure out parameters of

-     the new data2 and bss sections.  */

-

-  old_data_index = find_section (".data", old_section_names,

-				 old_name, old_file_h, old_section_h, 0);

-

   new_break = sbrk (0);

   new_bss_addr = (ElfW (Addr)) new_break;

-  new_data2_addr = old_bss_addr;

   new_data2_size = new_bss_addr - old_bss_addr;

   new_data2_offset = old_bss_offset;

@@ -722,7 +342,6 @@ unexec (const char *new_name, const char *old_name)

   DEBUG_LOG (old_bss_size);

   DEBUG_LOG (old_bss_offset);

   DEBUG_LOG (new_bss_addr);

-  DEBUG_LOG (new_data2_addr);

   DEBUG_LOG (new_data2_size);

   DEBUG_LOG (new_data2_offset);

 #endif

@@ -738,7 +357,7 @@ unexec (const char *new_name, const char *old_name)

   if (new_file < 0)

     fatal ("Can't creat (%s): %s", new_name, strerror (errno));

-  new_file_size = old_file_size + old_file_h->e_shentsize + new_data2_size;

+  new_file_size = old_file_size + new_data2_size;

   if (ftruncate (new_file, new_file_size))

     fatal ("Can't ftruncate (%s): %s", new_name, strerror (errno));

@@ -754,21 +373,18 @@ unexec (const char *new_name, const char *old_name)

   new_file_h = (ElfW (Ehdr) *) new_base;

   memcpy (new_file_h, old_file_h, old_file_h->e_ehsize);

-  /* Fix up file header.  We'll add one section.  Section header is

-     further away now.  */

+  /* Fix up file header.  Section header is further away now.  */

   if (new_file_h->e_shoff >= old_bss_offset)

     new_file_h->e_shoff += new_data2_size;

-  new_file_h->e_shnum += 1;

-

-  /* Modify the e_shstrndx if necessary. */

-  PATCH_INDEX (new_file_h->e_shstrndx);

   new_program_h = (ElfW (Phdr) *) ((byte *) new_base + new_file_h->e_phoff);

   new_section_h = (ElfW (Shdr) *) ((byte *) new_base + new_file_h->e_shoff);

   memcpy (new_program_h, old_program_h,

 	  old_file_h->e_phnum * old_file_h->e_phentsize);

+  memcpy (new_section_h, old_section_h,

+	  old_file_h->e_shnum * old_file_h->e_shentsize);

 #ifdef UNEXELF_DEBUG

   DEBUG_LOG (old_file_h->e_shoff);

@@ -787,42 +403,21 @@ unexec (const char *new_name, const char *old_name)

   /* Copy over what we have in memory now for the bss area. */

   memcpy (new_base + new_data2_offset, (caddr_t) old_bss_addr, new_data2_size);

-  /* Fix up section headers based on new .data2 section.  Any section

-     whose offset or virtual address is after the new .data2 section

-     gets its value adjusted.  .bss size becomes zero.  data2 section

-     header gets added by copying the existing .data header and

-     modifying the offset, address and size.  */

-

-  /* Walk through all section headers, insert the new data2 section right

-     before the new bss section. */

-  for (n = 1, nn = 1; n < old_file_h->e_shnum; n++, nn++)

+  /* Walk through all section headers, copying data and updating.  */

+  for (n = 1; n < old_file_h->e_shnum; n++)

     {

       caddr_t src;

       ElfW (Shdr) *old_shdr = &OLD_SECTION_H (n);

-      ElfW (Shdr) *new_shdr = &NEW_SECTION_H (nn);

-

-      /* If it is (s)bss section, insert the new data2 section before it.  */

-      if (n == old_bss_index)

-	{

-	  /* Steal the data section header for this data2 section. */

-	  memcpy (new_shdr, &OLD_SECTION_H (old_data_index),

-		  new_file_h->e_shentsize);

-

-	  new_shdr->sh_addr = new_data2_addr;

-	  new_shdr->sh_offset = new_data2_offset;

-	  new_shdr->sh_size = new_data2_size;

-	  new_shdr->sh_addralign = 1;

-	  nn++;

-	  new_shdr++;

-	}

-

-      memcpy (new_shdr, old_shdr, old_file_h->e_shentsize);

+      ElfW (Shdr) *new_shdr = &NEW_SECTION_H (n);

       if (new_shdr->sh_type == SHT_NOBITS

 	  && new_shdr->sh_addr >= old_bss_addr

 	  && (new_shdr->sh_addr + new_shdr->sh_size

 	      <= old_bss_addr + old_bss_size))

 	{

+	  /* This section now has file backing.  */

+	  new_shdr->sh_type = SHT_PROGBITS;

+

 	  /* SHT_NOBITS sections do not need a valid sh_offset, so it

 	     might be incorrect.  Write the correct value.  */

 	  new_shdr->sh_offset = (new_shdr->sh_addr - new_bss_seg->p_vaddr

@@ -837,35 +432,20 @@ unexec (const char *new_name, const char *old_name)

 	  if (strcmp (old_section_names + new_shdr->sh_name, ".plt") == 0)

 	    memset (new_shdr->sh_offset + new_base, 0, new_shdr->sh_size);

-	  /* Set the new bss and sbss section's size to zero, because

-	     we've already covered this address range by .data2.  */

-	  new_shdr->sh_size = 0;

-	}

-      else

-	{

-	  /* Any section that was originally placed after the .bss

-	     section should now be off by NEW_DATA2_SIZE.  */

+	  /* Extend the size of the last bss section to cover dumped

+	     data.  */

+	  if (n == old_bss_index)

+	    new_shdr->sh_size = new_bss_addr - new_shdr->sh_addr;

-	  if (new_shdr->sh_offset >= old_bss_offset)

-	    new_shdr->sh_offset += new_data2_size;

-

-	  /* Any section that was originally placed after the section

-	     header table should now be off by the size of one section

-	     header table entry.  */

-	  if (new_shdr->sh_offset > new_file_h->e_shoff)

-	    new_shdr->sh_offset += new_file_h->e_shentsize;

+	  /* We have already copied this section from the current

+	     process.  */

+	  continue;

 	}

-      /* If any section hdr refers to the section after the new .data

-	 section, make it refer to next one because we have inserted

-	 a new section in between.  */

-

-      PATCH_INDEX (new_shdr->sh_link);

-      /* For symbol tables, info is a symbol table index,

-	 so don't change it.  */

-      if (new_shdr->sh_type != SHT_SYMTAB

-	  && new_shdr->sh_type != SHT_DYNSYM)

-	PATCH_INDEX (new_shdr->sh_info);

+      /* Any section that was originally placed after the .bss

+	 section should now be offset by NEW_DATA2_SIZE.  */

+      if (new_shdr->sh_offset >= old_bss_offset)

+	new_shdr->sh_offset += new_data2_size;

       /* Now, start to copy the content of sections.  */

       if (new_shdr->sh_type == SHT_NULL

@@ -981,24 +561,6 @@ unexec (const char *new_name, const char *old_name)

 	    }

 	}

 #endif /* __sgi */

-

-      /* Patch st_shndx field of symbol table.  */

-      if (new_shdr->sh_type == SHT_SYMTAB

-	  || new_shdr->sh_type == SHT_DYNSYM)

-	{

-	  ptrdiff_t num = new_shdr->sh_size / new_shdr->sh_entsize;

-	  ElfW (Sym) *sym = (ElfW (Sym) *) (new_shdr->sh_offset + new_base);

-	  for (; num--; sym++)

-	    {

-	      if (sym->st_shndx == SHN_XINDEX)

-		fatal ("SHT_SYMTAB_SHNDX unsupported");

-	      if (sym->st_shndx == SHN_UNDEF

-		  || sym->st_shndx >= SHN_LORESERVE)

-		continue;

-

-	      PATCH_INDEX (sym->st_shndx);

-	    }

-	}

     }

   /* Update the symbol values of _edata and _end.  */

@@ -1042,15 +604,10 @@ unexec (const char *new_name, const char *old_name)

 	      ElfW (Shdr) *new_shdr = &NEW_SECTION_H (symp->st_shndx);

 	      if (new_shdr->sh_type != SHT_NOBITS)

 		{

-		  ElfW (Shdr) *old_shdr;

+		  ElfW (Shdr) *old_shdr = &OLD_SECTION_H (symp->st_shndx);

 		  ptrdiff_t reladdr = symp->st_value - new_shdr->sh_addr;

 		  ptrdiff_t newoff = reladdr + new_shdr->sh_offset;

-		  /* "Unpatch" index.  */

-		  nn = symp->st_shndx;

-		  if (nn > old_bss_index)

-		    nn--;

-		  old_shdr = &OLD_SECTION_H (nn);

 		  if (old_shdr->sh_type == SHT_NOBITS)

 		    memset (new_base + newoff, 0, symp->st_size);

 		  else

@@ -1065,6 +622,25 @@ unexec (const char *new_name, const char *old_name)

 	}

     }

+  /* Modify the names of sections we changed from SHT_NOBITS to

+     SHT_PROGBITS.  This is really just cosmetic, but some tools that

+     (wrongly) operate on section names rather than types might be

+     confused by a SHT_PROGBITS .bss section.  */

+  new_section_names = ((char *) new_base

+		       + NEW_SECTION_H (new_file_h->e_shstrndx).sh_offset);

+  for (n = new_file_h->e_shnum; 0 < --n; )

+    {

+      ElfW (Shdr) *old_shdr = &OLD_SECTION_H (n);

+      ElfW (Shdr) *new_shdr = &NEW_SECTION_H (n);

+

+      /* Replace the leading '.' with ','.  When .shstrtab is string

+	 merged this will rename both .bss and .rela.bss to ,bss and

+	 .rela,bss.  */

+      if (old_shdr->sh_type == SHT_NOBITS

+	  && new_shdr->sh_type == SHT_PROGBITS)

+	*(new_section_names + new_shdr->sh_name) = ',';

+    }

+

   /* This loop seeks out relocation sections for the data section, so

      that it can undo relocations performed by the runtime loader.  */

   for (n = new_file_h->e_shnum; 0 < --n; )

-- 

2.7.4