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Re: FRV and Blackfin PT_GNU_STACK
- From: Alan Modra <amodra at bigpond dot net dot au>
- To: Jie Zhang <jie dot zhang at analog dot com>
- Cc: binutils at sourceware dot org, Dave Brolley <brolley at redhat dot com>, Alexandre Oliva <aoliva at redhat dot com>, Bernd Schmidt <bernd dot schmidt at analog dot com>
- Date: Tue, 20 Jun 2006 21:13:17 +0930
- Subject: Re: FRV and Blackfin PT_GNU_STACK
- References: <20060619155936.GC13901@bubble.grove.modra.org> <1150793108.5570.13.camel@localhost.localdomain>
On Tue, Jun 20, 2006 at 04:45:08PM +0800, Jie Zhang wrote:
> On Tue, 2006-06-20 at 01:29 +0930, Alan Modra wrote:
> > When testing SIZEOF_HEADERS relaxation, I noticed that a fix in
> > http://sources.redhat.com/ml/binutils/2006-05/msg00318.html for PT_NOTE
> > p_memsz broke PT_GNU_STACK p_memsz for frv and bfin. To get this field
> > set, these ports create an output .stack section with the desired stack
> > size (and alignment) and tack it on to the PT_GNU_STACK header using
> > elf_backend_modify_segment_map. It's very much a hack, since you're not
> > supposed to create sections like this in the output bfd. One
> > consequence is that the .stack section header doesn't get its type
> > correct (you'd expect NOBITS) or size set (which is fortunate in a way,
> > because otherwise you'd end up with a large useless PROGBITS section in
> > the object file).
> >
> > The question I have is this: Do you want a .stack section in the output
> > file? Or should this section really be attached as an input section
> > that extends the .bss output section? Or do without the section
> > entirely and just magically tweak PT_GNU_STACK?
> >
> >From the code of binfmt_elf_fdpic.c in linux kernel, it seems the .stack
> section is not needed. The kernel gets the stack size for the FDPIC ELF
> application is from p_memsz of the PT_GNU_STACK segment.
>
> I'm not sure if my thought is right on why a .stack section is used
> here, since I'm not the original writer of the code. The .stack section
> is used to help set the PT_GNU_STACK segment size, since segment size is
> calculated by sum up the size of all the sections of it. If we want to
> eliminate the use of the section entirely, where can we magically tweak
> PT_GNU_STACK? Is there is already a hook we can use or we need add one?
Thanks for the feedback. Like you, I think the .stack section is only
there to set PT_GNU_STACK p_memsz and p_palign.
This is how I think FRV and Blackfin should set PT_GNU_STACK. No
messing around with a bogus .stack section. The new hook also allows me
to modify ia64 segments, so the final backend_modify_segment_map call
isn't needed.
* elf-bfd.h (struct elf_backend_data): Add
elf_backend_modify_program_headers.
* elfxx-target.h (elf_backend_modify_program_headers): Define.
(elfNN_bed): Init new field.
* elf.c (elf_modify_segment_map): Remove comment.
(assign_file_positions_for_load_sections): Only call
elf_modify_segment_map for objcopy/strip.
(assign_file_positions_except_relocs): Call
elf_backend_modify_program_headers.
* elf32-frv.c (elf32_frvfdpic_always_size_sections): Don't make
.stack section.
(elf32_frvfdpic_modify_segment_map): Delete.
(elf32_frvfdpic_modify_program_headers): New.
(elf_backend_modify_segment_map): Don't define.
(elf_backend_modify_program_headers): Define.
* elf32-bfin.c (elf32_bfinfdpic_always_size_sections): Don't make
.stack section.
(elf32_bfinfdpic_modify_segment_map): Delete.
(elf32_bfinfdpic_modify_program_headers): New.
(elf_backend_modify_segment_map): Don't define.
(elf_backend_modify_program_headers): Define.
* elfxx-ia64.c (elfNN_ia64_modify_program_headers): New function.
Split out from..
(elfNN_ia64_modify_segment_map): ..here.
(elf_backend_modify_program_headers): Define.
Index: bfd/elf-bfd.h
===================================================================
RCS file: /cvs/src/src/bfd/elf-bfd.h,v
retrieving revision 1.209
diff -u -p -r1.209 elf-bfd.h
--- bfd/elf-bfd.h 20 Jun 2006 02:22:13 -0000 1.209
+++ bfd/elf-bfd.h 20 Jun 2006 03:47:47 -0000
@@ -836,6 +836,11 @@ struct elf_backend_data
bfd_boolean (*elf_backend_modify_segment_map)
(bfd *, struct bfd_link_info *);
+ /* This function is called to modify program headers just before
+ they are written. */
+ bfd_boolean (*elf_backend_modify_program_headers)
+ (bfd *, struct bfd_link_info *);
+
/* This function is called during section garbage collection to
mark sections that define global symbols. */
bfd_boolean (*gc_mark_dynamic_ref)
Index: bfd/elfxx-target.h
===================================================================
RCS file: /cvs/src/src/bfd/elfxx-target.h,v
retrieving revision 1.95
diff -u -p -r1.95 elfxx-target.h
--- bfd/elfxx-target.h 30 May 2006 16:45:31 -0000 1.95
+++ bfd/elfxx-target.h 20 Jun 2006 03:48:02 -0000
@@ -402,6 +402,9 @@
#ifndef elf_backend_modify_segment_map
#define elf_backend_modify_segment_map 0
#endif
+#ifndef elf_backend_modify_program_headers
+#define elf_backend_modify_program_headers 0
+#endif
#ifndef elf_backend_ecoff_debug_swap
#define elf_backend_ecoff_debug_swap 0
#endif
@@ -603,6 +606,7 @@ static struct elf_backend_data elfNN_bed
elf_backend_final_write_processing,
elf_backend_additional_program_headers,
elf_backend_modify_segment_map,
+ elf_backend_modify_program_headers,
elf_backend_gc_mark_dynamic_ref,
elf_backend_gc_mark_hook,
elf_backend_gc_sweep_hook,
Index: bfd/elf.c
===================================================================
RCS file: /cvs/src/src/bfd/elf.c,v
retrieving revision 1.344
diff -u -p -r1.344 elf.c
--- bfd/elf.c 20 Jun 2006 02:22:13 -0000 1.344
+++ bfd/elf.c 20 Jun 2006 03:47:52 -0000
@@ -3733,8 +3733,6 @@ elf_modify_segment_map (bfd *abfd, struc
m->count = new_count;
}
- /* Yes, we call elf_backend_modify_segment_map at least two times
- for the linker. The final time the link_orders are available. */
bed = get_elf_backend_data (abfd);
if (bed->elf_backend_modify_segment_map != NULL)
{
@@ -4216,7 +4214,8 @@ assign_file_positions_for_load_sections
unsigned int alloc;
unsigned int i;
- if (!elf_modify_segment_map (abfd, link_info))
+ if (link_info == NULL
+ && !elf_modify_segment_map (abfd, link_info))
return FALSE;
alloc = 0;
@@ -4822,6 +4821,12 @@ assign_file_positions_except_relocs (bfd
if (!assign_file_positions_for_non_load_sections (abfd, link_info))
return FALSE;
+ if (bed->elf_backend_modify_program_headers != NULL)
+ {
+ if (!(*bed->elf_backend_modify_program_headers) (abfd, link_info))
+ return FALSE;
+ }
+
/* Write out the program headers. */
alloc = tdata->program_header_size / bed->s->sizeof_phdr;
if (bfd_seek (abfd, (bfd_signed_vma) bed->s->sizeof_ehdr, SEEK_SET) != 0
Index: bfd/elf32-frv.c
===================================================================
RCS file: /cvs/src/src/bfd/elf32-frv.c,v
retrieving revision 1.47
diff -u -p -r1.47 elf32-frv.c
--- bfd/elf32-frv.c 20 Jun 2006 02:22:13 -0000 1.47
+++ bfd/elf32-frv.c 20 Jun 2006 03:47:58 -0000
@@ -5603,7 +5603,6 @@ elf32_frvfdpic_always_size_sections (bfd
if (!info->relocatable)
{
struct elf_link_hash_entry *h;
- asection *sec;
/* Force a PT_GNU_STACK segment to be created. */
if (! elf_tdata (output_bfd)->stack_flags)
@@ -5630,13 +5629,6 @@ elf32_frvfdpic_always_size_sections (bfd
h->type = STT_OBJECT;
/* This one must NOT be hidden. */
}
-
- /* Create a stack section, and set its alignment. */
- sec = bfd_make_section (output_bfd, ".stack");
-
- if (sec == NULL
- || ! bfd_set_section_alignment (output_bfd, sec, 3))
- return FALSE;
}
return TRUE;
@@ -5718,51 +5710,45 @@ elf32_frvfdpic_relax_section (bfd *abfd
}
static bfd_boolean
-elf32_frvfdpic_modify_segment_map (bfd *output_bfd,
- struct bfd_link_info *info)
+elf32_frvfdpic_modify_program_headers (bfd *output_bfd,
+ struct bfd_link_info *info)
{
+ struct elf_obj_tdata *tdata = elf_tdata (output_bfd);
struct elf_segment_map *m;
+ Elf_Internal_Phdr *p;
/* objcopy and strip preserve what's already there using
elf32_frvfdpic_copy_private_bfd_data (). */
if (! info)
return TRUE;
- for (m = elf_tdata (output_bfd)->segment_map; m != NULL; m = m->next)
+ for (p = tdata->phdr, m = tdata->segment_map; m != NULL; m = m->next, p++)
if (m->p_type == PT_GNU_STACK)
break;
if (m)
{
- asection *sec = bfd_get_section_by_name (output_bfd, ".stack");
struct elf_link_hash_entry *h;
- if (sec)
+ /* Obtain the pointer to the __stacksize symbol. */
+ h = elf_link_hash_lookup (elf_hash_table (info), "__stacksize",
+ FALSE, FALSE, FALSE);
+ if (h)
{
- /* Obtain the pointer to the __stacksize symbol. */
- h = elf_link_hash_lookup (elf_hash_table (info), "__stacksize",
- FALSE, FALSE, FALSE);
while (h->root.type == bfd_link_hash_indirect
|| h->root.type == bfd_link_hash_warning)
- h = (struct elf_link_hash_entry *)h->root.u.i.link;
+ h = (struct elf_link_hash_entry *) h->root.u.i.link;
BFD_ASSERT (h->root.type == bfd_link_hash_defined);
+ }
- /* Set the section size from the symbol value. We
- intentionally ignore the symbol section. */
- if (h->root.type == bfd_link_hash_defined)
- sec->size = h->root.u.def.value;
- else
- sec->size = DEFAULT_STACK_SIZE;
+ /* Set the header p_memsz from the symbol value. We
+ intentionally ignore the symbol section. */
+ if (h && h->root.type == bfd_link_hash_defined)
+ p->p_memsz = h->root.u.def.value;
+ else
+ p->p_memsz = DEFAULT_STACK_SIZE;
- /* Add the stack section to the PT_GNU_STACK segment,
- such that its size and alignment requirements make it
- to the segment. */
- if (m->count == 0)
- {
- m->sections[m->count] = sec;
- m->count++;
- }
- }
+ p->p_align = 8;
}
return TRUE;
@@ -6973,9 +6959,9 @@ elf32_frv_grok_psinfo (bfd *abfd, Elf_In
#undef elf_backend_always_size_sections
#define elf_backend_always_size_sections \
elf32_frvfdpic_always_size_sections
-#undef elf_backend_modify_segment_map
-#define elf_backend_modify_segment_map \
- elf32_frvfdpic_modify_segment_map
+#undef elf_backend_modify_program_headers
+#define elf_backend_modify_program_headers \
+ elf32_frvfdpic_modify_program_headers
#undef bfd_elf32_bfd_copy_private_bfd_data
#define bfd_elf32_bfd_copy_private_bfd_data \
elf32_frvfdpic_copy_private_bfd_data
Index: bfd/elf32-bfin.c
===================================================================
RCS file: /cvs/src/src/bfd/elf32-bfin.c,v
retrieving revision 1.14
diff -u -p -r1.14 elf32-bfin.c
--- bfd/elf32-bfin.c 20 Jun 2006 02:22:13 -0000 1.14
+++ bfd/elf32-bfin.c 20 Jun 2006 03:56:43 -0000
@@ -4156,7 +4156,6 @@ elf32_bfinfdpic_always_size_sections (bf
if (!info->relocatable)
{
struct elf_link_hash_entry *h;
- asection *sec;
/* Force a PT_GNU_STACK segment to be created. */
if (! elf_tdata (output_bfd)->stack_flags)
@@ -4182,64 +4181,51 @@ elf32_bfinfdpic_always_size_sections (bf
h->def_regular = 1;
h->type = STT_OBJECT;
}
-
- /* Create a stack section, and set its alignment. */
- sec = bfd_make_section (output_bfd, ".stack");
-
- if (sec == NULL
- || ! bfd_set_section_alignment (output_bfd, sec, 3))
- return FALSE;
}
return TRUE;
}
static bfd_boolean
-elf32_bfinfdpic_modify_segment_map (bfd *output_bfd,
- struct bfd_link_info *info)
+elf32_bfinfdpic_modify_program_headers (bfd *output_bfd,
+ struct bfd_link_info *info)
{
+ struct elf_obj_tdata *tdata = elf_tdata (output_bfd);
struct elf_segment_map *m;
+ Elf_Internal_Phdr *p;
/* objcopy and strip preserve what's already there using
elf32_bfinfdpic_copy_private_bfd_data (). */
if (! info)
return TRUE;
- for (m = elf_tdata (output_bfd)->segment_map; m != NULL; m = m->next)
+ for (p = tdata->phdr, m = tdata->segment_map; m != NULL; m = m->next, p++)
if (m->p_type == PT_GNU_STACK)
break;
if (m)
{
- asection *sec = bfd_get_section_by_name (output_bfd, ".stack");
struct elf_link_hash_entry *h;
- if (sec)
+ /* Obtain the pointer to the __stacksize symbol. */
+ h = elf_link_hash_lookup (elf_hash_table (info), "__stacksize",
+ FALSE, FALSE, FALSE);
+ if (h)
{
- /* Obtain the pointer to the __stacksize symbol. */
- h = elf_link_hash_lookup (elf_hash_table (info), "__stacksize",
- FALSE, FALSE, FALSE);
while (h->root.type == bfd_link_hash_indirect
|| h->root.type == bfd_link_hash_warning)
- h = (struct elf_link_hash_entry *)h->root.u.i.link;
+ h = (struct elf_link_hash_entry *) h->root.u.i.link;
BFD_ASSERT (h->root.type == bfd_link_hash_defined);
+ }
- /* Set the section size from the symbol value. We
- intentionally ignore the symbol section. */
- if (h->root.type == bfd_link_hash_defined)
- sec->size = h->root.u.def.value;
- else
- sec->size = DEFAULT_STACK_SIZE;
+ /* Set the header p_memsz from the symbol value. We
+ intentionally ignore the symbol section. */
+ if (h && h->root.type == bfd_link_hash_defined)
+ p->p_memsz = h->root.u.def.value;
+ else
+ p->p_memsz = DEFAULT_STACK_SIZE;
- /* Add the stack section to the PT_GNU_STACK segment,
- such that its size and alignment requirements make it
- to the segment. */
- if (m->count == 0)
- {
- m->sections[m->count] = sec;
- m->count++;
- }
- }
+ p->p_align = 8;
}
return TRUE;
@@ -5594,9 +5580,9 @@ error_return:
#undef elf_backend_always_size_sections
#define elf_backend_always_size_sections \
elf32_bfinfdpic_always_size_sections
-#undef elf_backend_modify_segment_map
-#define elf_backend_modify_segment_map \
- elf32_bfinfdpic_modify_segment_map
+#undef elf_backend_modify_program_headers
+#define elf_backend_modify_program_headers \
+ elf32_bfinfdpic_modify_program_headers
#undef bfd_elf32_bfd_copy_private_bfd_data
#define bfd_elf32_bfd_copy_private_bfd_data \
elf32_bfinfdpic_copy_private_bfd_data
Index: bfd/elfxx-ia64.c
===================================================================
RCS file: /cvs/src/src/bfd/elfxx-ia64.c,v
retrieving revision 1.186
diff -u -p -r1.186 elfxx-ia64.c
--- bfd/elfxx-ia64.c 20 Jun 2006 02:22:13 -0000 1.186
+++ bfd/elfxx-ia64.c 20 Jun 2006 03:48:02 -0000
@@ -1737,17 +1737,30 @@ elfNN_ia64_modify_segment_map (bfd *abfd
}
}
- /* Turn on PF_IA_64_NORECOV if needed. This involves traversing all of
- the input sections for each output section in the segment and testing
- for SHF_IA_64_NORECOV on each. */
- for (m = elf_tdata (abfd)->segment_map; m != NULL; m = m->next)
+ return TRUE;
+}
+
+/* Turn on PF_IA_64_NORECOV if needed. This involves traversing all of
+ the input sections for each output section in the segment and testing
+ for SHF_IA_64_NORECOV on each. */
+
+static bfd_boolean
+elfNN_ia64_modify_program_headers (bfd *abfd,
+ struct bfd_link_info *info ATTRIBUTE_UNUSED)
+{
+ struct elf_obj_tdata *tdata = elf_tdata (abfd);
+ struct elf_segment_map *m;
+ Elf_Internal_Phdr *p;
+
+ for (p = tdata->phdr, m = tdata->segment_map; m != NULL; m = m->next, p++)
if (m->p_type == PT_LOAD)
{
int i;
for (i = m->count - 1; i >= 0; --i)
{
struct bfd_link_order *order = m->sections[i]->map_head.link_order;
- while (order)
+
+ while (order != NULL)
{
if (order->type == bfd_indirect_link_order)
{
@@ -1755,7 +1768,7 @@ elfNN_ia64_modify_segment_map (bfd *abfd
bfd_vma flags = elf_section_data(is)->this_hdr.sh_flags;
if (flags & SHF_IA_64_NORECOV)
{
- m->p_flags |= PF_IA_64_NORECOV;
+ p->p_flags |= PF_IA_64_NORECOV;
goto found;
}
}
@@ -5728,6 +5741,8 @@ elfNN_hpux_backend_symbol_processing (bf
elfNN_ia64_additional_program_headers
#define elf_backend_modify_segment_map \
elfNN_ia64_modify_segment_map
+#define elf_backend_modify_program_headers \
+ elfNN_ia64_modify_program_headers
#define elf_info_to_howto \
elfNN_ia64_info_to_howto
--
Alan Modra
IBM OzLabs - Linux Technology Centre