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ehdr_start twiddles

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We force __ehdr_start to defined in before_allocation, then restore
the type and a union after dynamic symbols have been allocated.
The union contains a number of structs, all starting with a "next"
pointer, and various fields depending on the symbol type.  The old
code restored the entire union, but it isn't necessary to restore the
"next" pointer, and in fact it could be wrong if __ehdr_start happened
to be last on the list and some symbols were added before restoring.

	* emultempl/elf32.em (before_allocation): Don't restore
	__ehdr_start u.*.next pointer.
This commit is contained in:
Alan Modra 2018-08-24 17:37:53 +09:30
parent 4575aaa964
commit 772758ac42
2 changed files with 21 additions and 12 deletions
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5
ld/ChangeLog
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@ -1,3 +1,8 @@
2018-08-24 Alan Modra <amodra@gmail.com>
* emultempl/elf32.em (before_allocation): Don't restore
__ehdr_start u.*.next pointer.
2018-08-23 Alan Modra <amodra@gmail.com>
PR 23566

28
ld/emultempl/elf32.em
View file

@ -1689,12 +1689,11 @@ gld${EMULATION_NAME}_before_allocation (void)
const char *rpath;
asection *sinterp;
bfd *abfd;
struct elf_link_hash_entry *ehdr_start = NULL;
struct bfd_link_hash_entry ehdr_start_save;
struct bfd_link_hash_entry *ehdr_start = NULL;
unsigned char ehdr_start_save_type = 0;
char ehdr_start_save_u[sizeof ehdr_start->u
- sizeof ehdr_start->u.def.next] = "";
/* The memset is here only to silence brain-dead compiler warnings
that the variable may be used uninitialized. */
memset (&ehdr_start_save, 0, sizeof ehdr_start_save);
if (is_elf_hash_table (link_info.hash))
{
_bfd_elf_tls_setup (link_info.output_bfd, &link_info);
@ -1725,11 +1724,14 @@ gld${EMULATION_NAME}_before_allocation (void)
we most likely will need dynamic relocations for
__ehdr_start if we are building a PIE or shared
library. */
ehdr_start = h;
ehdr_start_save = h->root;
h->root.type = bfd_link_hash_defined;
h->root.u.def.section = bfd_abs_section_ptr;
h->root.u.def.value = 0;
ehdr_start = &h->root;
ehdr_start_save_type = ehdr_start->type;
memcpy (ehdr_start_save_u,
(char *) &ehdr_start->u + sizeof ehdr_start->u.def.next,
sizeof ehdr_start_save_u);
ehdr_start->type = bfd_link_hash_defined;
ehdr_start->u.def.section = bfd_abs_section_ptr;
ehdr_start->u.def.value = 0;
}
}
@ -1848,8 +1850,10 @@ ${ELF_INTERPRETER_SET_DEFAULT}
{
/* If we twiddled __ehdr_start to defined earlier, put it back
as it was. */
ehdr_start->root.type = ehdr_start_save.type;
ehdr_start->root.u = ehdr_start_save.u;
ehdr_start->type = ehdr_start_save_type;
memcpy ((char *) &ehdr_start->u + sizeof ehdr_start->u.def.next,
ehdr_start_save_u,
sizeof ehdr_start_save_u);
}
}