+
+ /* This is an feature for objcopy --only-keep-debug: When a section's type
+ is changed to NOBITS, we preserve the sh_link and sh_info fields so that
+ they can be matched up with the original. */
+ Elf_Internal_Shdr ** iheaders = elf_elfsections (ibfd);
+ Elf_Internal_Shdr ** oheaders = elf_elfsections (obfd);
+
+ if (iheaders != NULL && oheaders != NULL)
+ {
+ unsigned int i;
+
+ for (i = 0; i < elf_numsections (obfd); i++)
+ {
+ unsigned int j;
+ Elf_Internal_Shdr * oheader = oheaders[i];
+
+ if (oheader == NULL
+ || oheader->sh_type != SHT_NOBITS
+ || oheader->sh_size == 0
+ || (oheader->sh_info != 0 && oheader->sh_link != 0))
+ continue;
+
+ /* Scan for the matching section in the input bfd.
+ FIXME: We could use something better than a linear scan here.
+ Unfortunately we cannot compare names as the output string table
+ is empty, so instead we check size, address and type. */
+ for (j = 0; j < elf_numsections (ibfd); j++)
+ {
+ Elf_Internal_Shdr * iheader = iheaders[j];
+
+ /* Since --only-keep-debug turns all non-debug sections
+ into SHT_NOBITS sections, the output SHT_NOBITS type
+ matches any input type. */
+ if ((oheader->sh_type == SHT_NOBITS
+ || iheader->sh_type == oheader->sh_type)
+ && iheader->sh_flags == oheader->sh_flags
+ && iheader->sh_addralign == oheader->sh_addralign
+ && iheader->sh_entsize == oheader->sh_entsize
+ && iheader->sh_size == oheader->sh_size
+ && iheader->sh_addr == oheader->sh_addr
+ && (iheader->sh_info != oheader->sh_info
+ || iheader->sh_link != oheader->sh_link))
+ {
+ /* Note: Strictly speaking these assignments are wrong.
+ The sh_link and sh_info fields should point to the
+ relevent sections in the output BFD, which may not be in
+ the same location as they were in the input BFD. But the
+ whole point of this action is to preserve the original
+ values of the sh_link and sh_info fields, so that they
+ can be matched up with the section headers in the
+ original file. So strictly speaking we may be creating
+ an invalid ELF file, but it is only for a file that just
+ contains debug info and only for sections without any
+ contents. */
+ if (oheader->sh_link == 0)
+ oheader->sh_link = iheader->sh_link;
+ if (oheader->sh_info == 0)
+ oheader->sh_info = iheader->sh_info;
+ break;
+ }
+ }
+ }
+ }
+