/* Native Client support for ELF
- Copyright 2012 Free Software Foundation, Inc.
+ Copyright (C) 2012-2021 Free Software Foundation, Inc.
This file is part of BFD, the Binary File Descriptor library.
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place - Suite 330, Boston,
- MA 02111-1307, USA. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "sysdep.h"
#include "bfd.h"
+#include "libbfd.h"
#include "elf-bfd.h"
#include "elf-nacl.h"
#include "elf/common.h"
#include "elf/internal.h"
-static bfd_boolean
+static bool
segment_executable (struct elf_segment_map *seg)
{
if (seg->p_flags_valid)
else
{
/* The p_flags value has not been computed yet,
- so we have to look through the sections. */
+ so we have to look through the sections. */
unsigned int i;
for (i = 0; i < seg->count; ++i)
- if (seg->sections[i]->flags & SEC_CODE)
- return TRUE;
+ if (seg->sections[i]->flags & SEC_CODE)
+ return true;
}
- return FALSE;
+ return false;
}
/* Determine if this segment is eligible to receive the file and program
- headers. It must be non-executable and have contents. Its first
- section must start far enough past the page boundary to allow space
- for the headers. */
-static bfd_boolean
+ headers. It must be read-only and non-executable.
+ Its first section must start far enough past the page boundary to
+ allow space for the headers. */
+static bool
segment_eligible_for_headers (struct elf_segment_map *seg,
- bfd_vma maxpagesize, bfd_vma sizeof_headers)
+ bfd_vma minpagesize, bfd_vma sizeof_headers)
{
- bfd_boolean any_contents = FALSE;
unsigned int i;
- if (seg->count == 0 || seg->sections[0]->lma % maxpagesize < sizeof_headers)
- return FALSE;
+ if (seg->count == 0 || seg->sections[0]->lma % minpagesize < sizeof_headers)
+ return false;
for (i = 0; i < seg->count; ++i)
{
- if (seg->sections[i]->flags & SEC_CODE)
- return FALSE;
- if (seg->sections[i]->flags & SEC_HAS_CONTENTS)
- any_contents = TRUE;
+ if ((seg->sections[i]->flags & (SEC_CODE|SEC_READONLY)) != SEC_READONLY)
+ return false;
}
- return any_contents;
+ 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
+bool
nacl_modify_segment_map (bfd *abfd, struct bfd_link_info *info)
{
- struct elf_segment_map **m = &elf_tdata (abfd)->segment_map;
+ 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 = bfd_sizeof_headers (abfd, info);
- bfd_vma maxpagesize = get_elf_backend_data (abfd)->maxpagesize;
+ struct elf_segment_map **headers = NULL;
+ 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;
+ 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)
- {
- /* 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 (!segment_executable (*m))
- return TRUE;
- 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, maxpagesize,
- 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;
- }
- }
-
+ {
+ bool 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 * sizeof (asection *)));
+ if (newseg == NULL)
+ return false;
+ memcpy (newseg, seg, (sizeof (*newseg) - sizeof (asection *)
+ + 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. */
+ if (first_load == NULL)
+ 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 (headers == NULL
+ && segment_eligible_for_headers (seg, bed->minpagesize,
+ sizeof_headers))
+ headers = m;
+ }
m = &seg->next;
}
- if (first_load != last_load && moved_headers)
+ if (headers != NULL)
{
- /* 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;
+ struct elf_segment_map **last_load = NULL;
+ struct elf_segment_map *seg;
+
+ m = first_load;
+ while ((seg = *m) != NULL)
+ {
+ if (seg->p_type == PT_LOAD)
+ {
+ /* Clear the flags on any previous segment that
+ included the file header and phdrs. */
+ seg->includes_filehdr = 0;
+ seg->includes_phdrs = 0;
+ seg->no_sort_lma = 1;
+ /* Also strip out empty segments. */
+ if (seg->count == 0)
+ {
+ if (headers == &seg->next)
+ headers = m;
+ *m = seg->next;
+ continue;
+ }
+ last_load = m;
+ }
+ m = &seg->next;
+ }
+
+ /* This segment will include those headers instead. */
+ seg = *headers;
+ seg->includes_filehdr = 1;
+ seg->includes_phdrs = 1;
+
+ if (last_load != NULL && first_load != last_load && first_load != headers)
+ {
+ /* Put the first PT_LOAD header last. */
+ 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;
+ 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 ATTRIBUTE_UNUSED)
+bool
+nacl_modify_headers (bfd *abfd, struct bfd_link_info *info)
{
- struct elf_segment_map **m = &elf_tdata (abfd)->segment_map;
- 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)
+ ;
+ else
{
- if ((*m)->p_type == PT_LOAD && (*m)->includes_filehdr)
- break;
-
- m = &(*m)->next;
- ++p;
+ struct elf_segment_map **m = &elf_seg_map (abfd);
+ Elf_Internal_Phdr *phdr = elf_tdata (abfd)->phdr;
+ Elf_Internal_Phdr *p = phdr;
+
+ /* 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;
+ }
+ }
}
- 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;
-
- first_seg->next = next_next;
- *first_load_seg = next_seg;
-
- next_seg->next = first_next;
- *next_load_seg = first_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 _bfd_elf_modify_headers (abfd, info);
+}
- return TRUE;
+bool
+nacl_final_write_processing (bfd *abfd)
+{
+ struct elf_segment_map *seg;
+ for (seg = elf_seg_map (abfd); seg != NULL; seg = seg->next)
+ if (seg->p_type == PT_LOAD
+ && seg->count > 1
+ && seg->sections[seg->count - 1]->owner == NULL)
+ {
+ /* This is a fake section added in nacl_modify_segment_map, above.
+ It's not a real BFD section, so nothing wrote its contents.
+ Now write out its contents. */
+
+ asection *sec = seg->sections[seg->count - 1];
+ char *fill;
+
+ BFD_ASSERT (sec->flags & SEC_LINKER_CREATED);
+ BFD_ASSERT (sec->flags & SEC_CODE);
+ BFD_ASSERT (sec->size > 0);
+
+ fill = abfd->arch_info->fill (sec->size, bfd_big_endian (abfd), true);
+
+ if (fill == NULL
+ || bfd_seek (abfd, sec->filepos, SEEK_SET) != 0
+ || bfd_bwrite (fill, sec->size, abfd) != sec->size)
+ {
+ /* We don't have a proper way to report an error here. So
+ instead fudge things so that elf_write_shdrs_and_ehdr will
+ fail. */
+ elf_elfheader (abfd)->e_shoff = (file_ptr) -1;
+ }
+
+ free (fill);
+ }
+ return _bfd_elf_final_write_processing (abfd);
}
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