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PATCH: Map GNU attributes section to PT_GNU_ATTR (aka PT_GNU_STACK) segment
On Wed, Aug 15, 2007 at 05:39:48PM +0100, Nick Clifton wrote:
> Hi H.J.
>
> >The current usage of the PT_GNU_STACK segment is the flags field
> >only. All other fields are ignored. The new segment ignores the
> >flags field. Overloading the PT_GNU_STACK segment seems a good
> >idea to me since it is totally backward and forward compatible.
>
> I agree that it is forward and backward compatible. I am just worried that
> the name of the segment, if set to PT_GNU_ATTRIBUTES or left as
> PT_GNU_STACK, would be confusing. I think that we ought to have a more
> generic type of name and then have a well defined scheme for storing
> information in this segment.
I change it to PT_GNU_ATTR.
>
> >That is what my proposal does. The only difference is I call the
> >new segment PT_GNU_ATTRIBUTES. I don't mind we use a differrent
> >name at all. The loader-accessible information belongs to the GNU
> >attributes section and it is extendable.
>
> True, so maybe we ought to have a GNU_STACK attribute and use that. For
> backwards compatibility we can still set the flags of the segment
> appropriately, but that would only be for backwards compatibility. Any
> future uses of the segment would not make use of the flags to specify any
> information.
>
>
I am not sure if it is worth the change since a special note section,
.note.GNU-stack, is used to specify the stack flags. Moving it to
the .gnu.attributes section will require changes in gcc, binutils
and applications. We have to keep .note.GNU-stack because of it. We
can add new ones to .gnu.attributes, but should leave the stack flags
alone.
Thanks.
H.J.
---
bfd/
2007-08-15 H.J. Lu <hongjiu.lu@intel.com>
* elf.c (get_segment_type): Change PT_GNU_STACK to PT_GNU_ATTR.
(bfd_section_from_phdr): Likewise.
(get_program_header_size): Likewise. Add a PT_GNU_ATTR segment
if there is an attribute section.
(_bfd_elf_map_sections_to_segments): Likewise.
(IS_SECTION_IN_INPUT_SEGMENT): Likewise.
binutils/
2007-08-15 H.J. Lu <hongjiu.lu@intel.com>
* readelf.c (get_segment_type): Change PT_GNU_STACK to
PT_GNU_ATTR.
include/elf/
2007-08-15 H.J. Lu <hongjiu.lu@intel.com>
* common.h (PT_GNU_STACK): Renamed to ...
(PT_GNU_ATTR): This.
(PT_GNU_STACK): New. Make an alias of PT_GNU_ATTR.
--- binutils/bfd/elf.c.attri 2007-08-14 08:41:55.000000000 -0700
+++ binutils/bfd/elf.c 2007-08-15 10:04:21.000000000 -0700
@@ -1083,7 +1083,7 @@ get_segment_type (unsigned int p_type)
case PT_PHDR: pt = "PHDR"; break;
case PT_TLS: pt = "TLS"; break;
case PT_GNU_EH_FRAME: pt = "EH_FRAME"; break;
- case PT_GNU_STACK: pt = "STACK"; break;
+ case PT_GNU_ATTR: pt = "ATTR"; break;
case PT_GNU_RELRO: pt = "RELRO"; break;
default: pt = NULL; break;
}
@@ -2355,8 +2355,8 @@ bfd_section_from_phdr (bfd *abfd, Elf_In
return _bfd_elf_make_section_from_phdr (abfd, hdr, index,
"eh_frame_hdr");
- case PT_GNU_STACK:
- return _bfd_elf_make_section_from_phdr (abfd, hdr, index, "stack");
+ case PT_GNU_ATTR:
+ return _bfd_elf_make_section_from_phdr (abfd, hdr, index, "attr");
case PT_GNU_RELRO:
return _bfd_elf_make_section_from_phdr (abfd, hdr, index, "relro");
@@ -3300,7 +3300,8 @@ get_program_header_size (bfd *abfd, stru
{
size_t segs;
asection *s;
- const struct elf_backend_data *bed;
+ asection *attr = NULL;
+ const struct elf_backend_data *bed = get_elf_backend_data (abfd);
/* Assume we will need exactly two PT_LOAD segments: one for text
and one for data. */
@@ -3335,14 +3336,26 @@ get_program_header_size (bfd *abfd, stru
++segs;
}
- if (elf_tdata (abfd)->stack_flags)
- {
- /* We need a PT_GNU_STACK segment. */
- ++segs;
- }
-
for (s = abfd->sections; s != NULL; s = s->next)
{
+ if (elf_section_type (s) == bed->obj_attrs_section_type)
+ {
+ BFD_ASSERT (attr == NULL);
+ attr = s;
+
+ /* elf_tdata (abfd)->stack_flags is checked for the
+ PT_GNU_ATTR segment. If there is an attribute
+ section, we make sure that stack_flags isn't zero so
+ that the PT_GNU_ATTR segment will be created. */
+ if (! elf_tdata (abfd)->stack_flags)
+ {
+ if (bed->default_execstack)
+ elf_tdata (abfd)->stack_flags = PF_R | PF_W | PF_X;
+ else
+ elf_tdata (abfd)->stack_flags = PF_R | PF_W;
+ }
+ }
+
if ((s->flags & SEC_LOAD) != 0
&& CONST_STRNEQ (s->name, ".note"))
{
@@ -3364,6 +3377,12 @@ get_program_header_size (bfd *abfd, stru
}
}
+ if (elf_tdata (abfd)->stack_flags)
+ {
+ /* We need a PT_GNU_ATTR segment. */
+ ++segs;
+ }
+
for (s = abfd->sections; s != NULL; s = s->next)
{
if (s->flags & SEC_THREAD_LOCAL)
@@ -3375,7 +3394,6 @@ get_program_header_size (bfd *abfd, stru
}
/* Let the backend count up any program headers it might need. */
- bed = get_elf_backend_data (abfd);
if (bed->elf_backend_additional_program_headers)
{
int a;
@@ -3520,6 +3538,7 @@ _bfd_elf_map_sections_to_segments (bfd *
asection *first_tls = NULL;
asection *dynsec, *eh_frame_hdr;
bfd_size_type amt;
+ asection *attr = NULL;
/* Select the allocated sections, and sort them. */
@@ -3530,6 +3549,12 @@ _bfd_elf_map_sections_to_segments (bfd *
i = 0;
for (s = abfd->sections; s != NULL; s = s->next)
{
+ if (elf_section_type (s) == bed->obj_attrs_section_type)
+ {
+ BFD_ASSERT (attr == NULL);
+ attr = s;
+ }
+
if ((s->flags & SEC_ALLOC) != 0)
{
sections[i] = s;
@@ -3843,10 +3868,17 @@ _bfd_elf_map_sections_to_segments (bfd *
if (m == NULL)
goto error_return;
m->next = NULL;
- m->p_type = PT_GNU_STACK;
+ m->p_type = PT_GNU_ATTR;
m->p_flags = elf_tdata (abfd)->stack_flags;
m->p_flags_valid = 1;
+ if (attr)
+ {
+ /* Add the attribute section if needed. */
+ m->count = 1;
+ m->sections[0] = attr;
+ }
+
*pm = m;
pm = &m->next;
}
@@ -5033,31 +5065,33 @@ rewrite_elf_program_header (bfd *ibfd, b
2. It is an allocated segment,
3. There is an output section associated with it,
4. The section has not already been allocated to a previous segment.
- 5. PT_GNU_STACK segments do not include any sections.
+ 5. PT_GNU_ATTR only contains attribute section.
6. PT_TLS segment includes only SHF_TLS sections.
7. SHF_TLS sections are only in PT_TLS or PT_LOAD segments.
8. PT_DYNAMIC should not contain empty sections at the beginning
(with the possible exception of .dynamic). */
#define IS_SECTION_IN_INPUT_SEGMENT(section, segment, bed) \
- ((((segment->p_paddr \
- ? IS_CONTAINED_BY_LMA (section, segment, segment->p_paddr) \
- : IS_CONTAINED_BY_VMA (section, segment)) \
- && (section->flags & SEC_ALLOC) != 0) \
- || IS_COREFILE_NOTE (segment, section)) \
- && segment->p_type != PT_GNU_STACK \
- && (segment->p_type != PT_TLS \
- || (section->flags & SEC_THREAD_LOCAL)) \
- && (segment->p_type == PT_LOAD \
- || segment->p_type == PT_TLS \
- || (section->flags & SEC_THREAD_LOCAL) == 0) \
- && (segment->p_type != PT_DYNAMIC \
- || SECTION_SIZE (section, segment) > 0 \
- || (segment->p_paddr \
- ? segment->p_paddr != section->lma \
- : segment->p_vaddr != section->vma) \
- || (strcmp (bfd_get_section_name (ibfd, section), ".dynamic") \
- == 0)) \
- && ! section->segment_mark)
+ ((segment->p_type == PT_GNU_ATTR \
+ && elf_section_type (section) == bed->obj_attrs_section_type) \
+ || ((((segment->p_paddr \
+ ? IS_CONTAINED_BY_LMA (section, segment, segment->p_paddr) \
+ : IS_CONTAINED_BY_VMA (section, segment)) \
+ && (section->flags & SEC_ALLOC) != 0) \
+ || IS_COREFILE_NOTE (segment, section)) \
+ && segment->p_type != PT_GNU_ATTR \
+ && (segment->p_type != PT_TLS \
+ || (section->flags & SEC_THREAD_LOCAL)) \
+ && (segment->p_type == PT_LOAD \
+ || segment->p_type == PT_TLS \
+ || (section->flags & SEC_THREAD_LOCAL) == 0) \
+ && (segment->p_type != PT_DYNAMIC \
+ || SECTION_SIZE (section, segment) > 0 \
+ || (segment->p_paddr \
+ ? segment->p_paddr != section->lma \
+ : segment->p_vaddr != section->vma) \
+ || (strcmp (bfd_get_section_name (ibfd, section), \
+ ".dynamic") == 0)) \
+ && ! section->segment_mark))
/* If the output section of a section in the input segment is NULL,
it is removed from the corresponding output segment. */
--- binutils/binutils/readelf.c.attri 2007-07-27 12:52:07.000000000 -0700
+++ binutils/binutils/readelf.c 2007-08-15 09:55:17.000000000 -0700
@@ -2467,7 +2467,7 @@ get_segment_type (unsigned long p_type)
case PT_GNU_EH_FRAME:
return "GNU_EH_FRAME";
- case PT_GNU_STACK: return "GNU_STACK";
+ case PT_GNU_ATTR: return "GNU_ATTR";
case PT_GNU_RELRO: return "GNU_RELRO";
default:
--- binutils/include/elf/common.h.attri 2007-07-24 15:03:52.000000000 -0700
+++ binutils/include/elf/common.h 2007-08-15 09:49:15.000000000 -0700
@@ -307,7 +307,8 @@
#define PT_GNU_EH_FRAME (PT_LOOS + 0x474e550) /* Frame unwind information */
#define PT_SUNW_EH_FRAME PT_GNU_EH_FRAME /* Solaris uses the same value */
-#define PT_GNU_STACK (PT_LOOS + 0x474e551) /* Stack flags */
+#define PT_GNU_ATTR (PT_LOOS + 0x474e551) /* Attribute info */
+#define PT_GNU_STACK PT_GNU_ATTR /* Stack flags */
#define PT_GNU_RELRO (PT_LOOS + 0x474e552) /* Read-only after relocation */
/* Program segment permissions, in program header p_flags field. */