bfd_boolean
bfd_record_phdr (bfd *abfd,
unsigned long type,
bfd_boolean flags_valid,
flagword flags,
bfd_boolean at_valid,
bfd_vma at,
bfd_boolean includes_filehdr,
bfd_boolean includes_phdrs,
unsigned int count,
asection **secs)
{
struct elf_segment_map *m, **pm;
bfd_size_type amt;
if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
return TRUE;
amt = sizeof (struct elf_segment_map);
amt += ((bfd_size_type) count - 1) * sizeof (asection *);
m = (struct elf_segment_map *) bfd_zalloc (abfd, amt);
if (m == NULL)
return FALSE;
m->p_type = type;
m->p_flags = flags;
m->p_paddr = at;
m->p_flags_valid = flags_valid;
m->p_paddr_valid = at_valid;
m->includes_filehdr = includes_filehdr;
m->includes_phdrs = includes_phdrs;
m->count = count;
if (count > 0)
memcpy (m->sections, secs, count * sizeof (asection *));
for (pm = &elf_seg_map (abfd); *pm != NULL; pm = &(*pm)->next)
;
*pm = m;
return TRUE;
}
/* We permute the segment_map to get BFD to do the file layout we want:
The first non-executable PT_LOAD segment appears first in the file
and contains the ELF file header and phdrs. */
bfd_boolean
nacl_modify_segment_map (bfd *abfd, struct bfd_link_info *info)
{
const struct elf_backend_data *const bed = get_elf_backend_data (abfd);
struct elf_segment_map **m = &elf_seg_map (abfd);
struct elf_segment_map **first_load = NULL;
struct elf_segment_map **last_load = NULL;
bfd_boolean moved_headers = FALSE;
int sizeof_headers;
if (info != NULL && info->user_phdrs)
/* The linker script used PHDRS explicitly, so don't change what the
user asked for. */
return TRUE;
if (info != NULL)
/* We're doing linking, so evalute SIZEOF_HEADERS as in a linker script. */
sizeof_headers = bfd_sizeof_headers (abfd, info);
else
{
/* We're not doing linking, so this is objcopy or suchlike.
We just need to collect the size of the existing headers. */
struct elf_segment_map *seg;
sizeof_headers = bed->s->sizeof_ehdr;
for (seg = *m; seg != NULL; seg = seg->next)
sizeof_headers += bed->s->sizeof_phdr;
}
while (*m != NULL)
{
struct elf_segment_map *seg = *m;
if (seg->p_type == PT_LOAD)
{
bfd_boolean executable = segment_executable (seg);
if (executable
&& seg->count > 0
&& seg->sections[0]->vma % bed->minpagesize == 0)
{
asection *lastsec = seg->sections[seg->count - 1];
bfd_vma end = lastsec->vma + lastsec->size;
if (end % bed->minpagesize != 0)
{
/* This is an executable segment that starts on a page
boundary but does not end on a page boundary. Fill
it out to a whole page with code fill (the tail of
the segment will not be within any section). Thus
the entire code segment can be mapped from the file
as whole pages and that mapping will contain only
valid instructions.
To accomplish this, we must fake out the code in
assign_file_positions_for_load_sections (elf.c) so
that it advances past the rest of the final page,
rather than trying to put the next (unaligned, or
unallocated) section. We do this by appending a
dummy section record to this element in the segment
map. No such output section ever actually exists,
but this gets the layout logic to advance the file
positions past this partial page. Since we are
lying to BFD like this, nothing will ever know to
write the section contents. So we do that by hand
after the fact, in nacl_final_write_processing, below. */
struct elf_segment_map *newseg;
asection *sec;
struct bfd_elf_section_data *secdata;
BFD_ASSERT (!seg->p_size_valid);
secdata = bfd_zalloc (abfd, sizeof *secdata);
if (secdata == NULL)
return FALSE;
sec = bfd_zalloc (abfd, sizeof *sec);
if (sec == NULL)
return FALSE;
/* Fill in only the fields that actually affect the logic
in assign_file_positions_for_load_sections. */
sec->vma = end;
sec->lma = lastsec->lma + lastsec->size;
sec->size = bed->minpagesize - (end % bed->minpagesize);
sec->flags = (SEC_ALLOC | SEC_LOAD
| SEC_READONLY | SEC_CODE | SEC_LINKER_CREATED);
sec->used_by_bfd = secdata;
secdata->this_hdr.sh_type = SHT_PROGBITS;
secdata->this_hdr.sh_flags = SHF_ALLOC | SHF_EXECINSTR;
secdata->this_hdr.sh_addr = sec->vma;
secdata->this_hdr.sh_size = sec->size;
newseg = bfd_alloc (abfd,
sizeof *newseg + ((seg->count + 1)
* sizeof (asection *)));
if (newseg == NULL)
return FALSE;
memcpy (newseg, seg,
sizeof *newseg + (seg->count * sizeof (asection *)));
newseg->sections[newseg->count++] = sec;
*m = seg = newseg;
}
}
/* First, we're just finding the earliest PT_LOAD.
By the normal rules, this will be the lowest-addressed one.
We only have anything interesting to do if it's executable. */
last_load = m;
if (first_load == NULL)
{
if (!executable)
goto next;
first_load = m;
}
/* Now that we've noted the first PT_LOAD, we're looking for
the first non-executable PT_LOAD with a nonempty p_filesz. */
else if (!moved_headers
&& segment_eligible_for_headers (seg, bed->minpagesize,
sizeof_headers))
{
/* This is the one we were looking for!
First, clear the flags on previous segments that
say they include the file header and phdrs. */
struct elf_segment_map *prevseg;
for (prevseg = *first_load;
prevseg != seg;
prevseg = prevseg->next)
if (prevseg->p_type == PT_LOAD)
{
prevseg->includes_filehdr = 0;
prevseg->includes_phdrs = 0;
}
/* This segment will include those headers instead. */
seg->includes_filehdr = 1;
seg->includes_phdrs = 1;
moved_headers = TRUE;
}
}
next:
m = &seg->next;
}
if (first_load != last_load && moved_headers)
{
/* Now swap the first and last PT_LOAD segments'
positions in segment_map. */
struct elf_segment_map *first = *first_load;
struct elf_segment_map *last = *last_load;
*first_load = first->next;
first->next = last->next;
last->next = first;
}
return TRUE;
}
/* After nacl_modify_segment_map has done its work, the file layout has
been done as we wanted. But the PT_LOAD phdrs are no longer in the
proper order for the ELF rule that they must appear in ascending address
order. So find the two segments we swapped before, and swap them back. */
bfd_boolean
nacl_modify_program_headers (bfd *abfd, struct bfd_link_info *info)
{
struct elf_segment_map **m = &elf_seg_map (abfd);
Elf_Internal_Phdr *phdr = elf_tdata (abfd)->phdr;
Elf_Internal_Phdr *p = phdr;
if (info != NULL && info->user_phdrs)
/* The linker script used PHDRS explicitly, so don't change what the
user asked for. */
return TRUE;
/* Find the PT_LOAD that contains the headers (should be the first). */
while (*m != NULL)
{
if ((*m)->p_type == PT_LOAD && (*m)->includes_filehdr)
break;
m = &(*m)->next;
++p;
}
if (*m != NULL)
{
struct elf_segment_map **first_load_seg = m;
Elf_Internal_Phdr *first_load_phdr = p;
struct elf_segment_map **next_load_seg = NULL;
Elf_Internal_Phdr *next_load_phdr = NULL;
/* Now move past that first one and find the PT_LOAD that should be
before it by address order. */
m = &(*m)->next;
++p;
while (*m != NULL)
{
if (p->p_type == PT_LOAD && p->p_vaddr < first_load_phdr->p_vaddr)
{
next_load_seg = m;
next_load_phdr = p;
break;
}
m = &(*m)->next;
++p;
}
/* Swap their positions in the segment_map back to how they used to be.
The phdrs have already been set up by now, so we have to slide up
the earlier ones to insert the one that should be first. */
if (next_load_seg != NULL)
{
Elf_Internal_Phdr move_phdr;
struct elf_segment_map *first_seg = *first_load_seg;
struct elf_segment_map *next_seg = *next_load_seg;
struct elf_segment_map *first_next = first_seg->next;
struct elf_segment_map *next_next = next_seg->next;
if (next_load_seg == &first_seg->next)
{
*first_load_seg = next_seg;
next_seg->next = first_seg;
first_seg->next = next_next;
}
else
{
*first_load_seg = first_next;
*next_load_seg = next_next;
first_seg->next = *next_load_seg;
*next_load_seg = first_seg;
next_seg->next = *first_load_seg;
*first_load_seg = next_seg;
}
move_phdr = *next_load_phdr;
memmove (first_load_phdr + 1, first_load_phdr,
(next_load_phdr - first_load_phdr) * sizeof move_phdr);
*first_load_phdr = move_phdr;
}
}
return TRUE;
}
