powerpc64-ld: section exceeds stub group size
Alan Modra
amodra@bigpond.net.au
Tue Nov 7 03:33:00 GMT 2006
There have been rather a lot of complaints about the warnings emitted
by the linker when building a powerpc64 linux kernel. Up until now
I've resisted doing anything about them, because the warnings proved
useful in tracking down problems with large apps. Also, I thought
they were avoidable if the kernel people would see the light and not
use "ld -r" as a means of packaging object files. Well, it seems that
I was wrong. "ld -r" wasn't the real cause. Instead, the warnings
were due to some suspect assembly in head_64.S involving conditional
branches to global symbols. Conditional branches on powerpc have a
rather limited range, and it was these branches that caused ld to
use a small stub group size. In the process of finding these
problems, Paul Mackerras wondered why ld was warning about other
sections that didn't have such conditional branches. Of course, there
isn't any good reason for warning against those sections.
This patch teaches powerpc64 ld to pack sections into groups sized
according to each individual section's needs, rather than using a
group size determined by the minimum over all sections. Besides
reducing the number of warnings, this helps pack sections better.
I've also turned off the warning entirely if the default group size is
used.
* elf64-ppc.c (enum _ppc64_sec_type): New.
(struct _ppc64_elf_section_data): Move "t_symndx" into opd union,
and rename fields. Add sec_type and has_14bit_branch.
(struct ppc_link_hash_table): Remove has_14bit_branch.
(get_opd_info, get_tls_mask, ppc64_elf_edit_opd): Adjust.
(ppc64_elf_relocate_section): Likewise.
(ppc64_elf_check_relocs): Likewise. Set per-section has_14bit_branch.
(ppc64_elf_size_stubs): Don't set default group size here.
(group_sections): Instead do so here, and group sections using
their individual requirements.
Index: bfd/elf64-ppc.c
===================================================================
RCS file: /cvs/src/src/bfd/elf64-ppc.c,v
retrieving revision 1.251
diff -u -p -r1.251 elf64-ppc.c
--- bfd/elf64-ppc.c 7 Nov 2006 03:24:13 -0000 1.251
+++ bfd/elf64-ppc.c 7 Nov 2006 03:25:46 -0000
@@ -2525,6 +2525,12 @@ static const struct bfd_elf_special_sect
{ NULL, 0, 0, 0, 0 }
};
+enum _ppc64_sec_type {
+ sec_normal = 0,
+ sec_opd = 1,
+ sec_toc = 2
+};
+
struct _ppc64_elf_section_data
{
struct bfd_elf_section_data elf;
@@ -2533,14 +2539,20 @@ struct _ppc64_elf_section_data
union
{
/* Points to the function code section for local opd entries. */
- asection **func_sec;
+ asection **opd_func_sec;
/* After editing .opd, adjust references to opd local syms. */
- long *adjust;
- } opd;
+ long *opd_adjust;
+
+ /* An array for toc sections, indexed by offset/8.
+ Specifies the relocation symbol index used at a given toc offset. */
+ unsigned *t_symndx;
+ } u;
+
+ enum _ppc64_sec_type sec_type:2;
- /* An array for toc sections, indexed by offset/8.
- Specifies the relocation symbol index used at a given toc offset. */
- unsigned *t_symndx;
+ /* Flag set when small branches are detected. Used to
+ select suitable defaults for the stub group size. */
+ unsigned int has_14bit_branch:1;
};
#define ppc64_elf_section_data(sec) \
@@ -2568,8 +2580,8 @@ get_opd_info (asection * sec)
{
if (sec != NULL
&& ppc64_elf_section_data (sec) != NULL
- && ppc64_elf_section_data (sec)->opd.adjust != NULL)
- return ppc64_elf_section_data (sec)->opd.adjust;
+ && ppc64_elf_section_data (sec)->sec_type == sec_opd)
+ return ppc64_elf_section_data (sec)->u.opd_adjust;
return NULL;
}
@@ -3358,10 +3370,6 @@ struct ppc_link_hash_table
/* Set on error. */
unsigned int stub_error:1;
- /* Flag set when small branches are detected. Used to
- select suitable defaults for the stub group size. */
- unsigned int has_14bit_branch:1;
-
/* Temp used by ppc64_elf_check_directives. */
unsigned int twiddled_syms:1;
@@ -4373,7 +4381,9 @@ ppc64_elf_check_relocs (bfd *abfd, struc
opd_sym_map = bfd_zalloc (abfd, amt);
if (opd_sym_map == NULL)
return FALSE;
- ppc64_elf_section_data (sec)->opd.func_sec = opd_sym_map;
+ ppc64_elf_section_data (sec)->u.opd_func_sec = opd_sym_map;
+ BFD_ASSERT (ppc64_elf_section_data (sec)->sec_type == sec_normal);
+ ppc64_elf_section_data (sec)->sec_type = sec_opd;
}
if (htab->sfpr == NULL
@@ -4387,6 +4397,7 @@ ppc64_elf_check_relocs (bfd *abfd, struc
struct elf_link_hash_entry *h;
enum elf_ppc64_reloc_type r_type;
int tls_type = 0;
+ struct _ppc64_elf_section_data *ppc64_sec;
r_symndx = ELF64_R_SYM (rel->r_info);
if (r_symndx < symtab_hdr->sh_info)
@@ -4568,7 +4579,7 @@ ppc64_elf_check_relocs (bfd *abfd, struc
dest = bfd_section_from_r_symndx (abfd, &htab->sym_sec,
sec, r_symndx);
if (dest != sec)
- htab->has_14bit_branch = 1;
+ ppc64_elf_section_data (sec)->has_14bit_branch = 1;
}
/* Fall through. */
@@ -4639,23 +4650,26 @@ ppc64_elf_check_relocs (bfd *abfd, struc
rel->r_addend, tls_type))
return FALSE;
- if (ppc64_elf_section_data (sec)->t_symndx == NULL)
+ ppc64_sec = ppc64_elf_section_data (sec);
+ if (ppc64_sec->sec_type != sec_toc)
{
/* One extra to simplify get_tls_mask. */
bfd_size_type amt = sec->size * sizeof (unsigned) / 8 + 1;
- ppc64_elf_section_data (sec)->t_symndx = bfd_zalloc (abfd, amt);
- if (ppc64_elf_section_data (sec)->t_symndx == NULL)
+ ppc64_sec->u.t_symndx = bfd_zalloc (abfd, amt);
+ if (ppc64_sec->u.t_symndx == NULL)
return FALSE;
+ BFD_ASSERT (ppc64_sec->sec_type == sec_normal);
+ ppc64_sec->sec_type = sec_toc;
}
BFD_ASSERT (rel->r_offset % 8 == 0);
- ppc64_elf_section_data (sec)->t_symndx[rel->r_offset / 8] = r_symndx;
+ ppc64_sec->u.t_symndx[rel->r_offset / 8] = r_symndx;
/* Mark the second slot of a GD or LD entry.
-1 to indicate GD and -2 to indicate LD. */
if (tls_type == (TLS_EXPLICIT | TLS_TLS | TLS_GD))
- ppc64_elf_section_data (sec)->t_symndx[rel->r_offset / 8 + 1] = -1;
+ ppc64_sec->u.t_symndx[rel->r_offset / 8 + 1] = -1;
else if (tls_type == (TLS_EXPLICIT | TLS_TLS | TLS_LD))
- ppc64_elf_section_data (sec)->t_symndx[rel->r_offset / 8 + 1] = -2;
+ ppc64_sec->u.t_symndx[rel->r_offset / 8 + 1] = -2;
goto dodyn;
case R_PPC64_TPREL16:
@@ -6051,7 +6065,7 @@ get_tls_mask (char **tls_maskp, unsigned
if ((*tls_maskp != NULL && **tls_maskp != 0)
|| sec == NULL
- || ppc64_elf_section_data (sec)->t_symndx == NULL)
+ || ppc64_elf_section_data (sec)->sec_type != sec_toc)
return 1;
/* Look inside a TOC section too. */
@@ -6064,8 +6078,8 @@ get_tls_mask (char **tls_maskp, unsigned
off = sym->st_value;
off += rel->r_addend;
BFD_ASSERT (off % 8 == 0);
- r_symndx = ppc64_elf_section_data (sec)->t_symndx[off / 8];
- next_r = ppc64_elf_section_data (sec)->t_symndx[off / 8 + 1];
+ r_symndx = ppc64_elf_section_data (sec)->u.t_symndx[off / 8];
+ next_r = ppc64_elf_section_data (sec)->u.t_symndx[off / 8 + 1];
if (!get_sym_h (&h, &sym, &sec, tls_maskp, locsymsp, r_symndx, ibfd))
return 0;
if (toc_symndx != NULL)
@@ -6306,7 +6320,9 @@ ppc64_elf_edit_opd (bfd *obfd, struct bf
opd_adjust = bfd_alloc (obfd, amt);
if (opd_adjust == NULL)
return FALSE;
- ppc64_elf_section_data (sec)->opd.adjust = opd_adjust;
+ ppc64_elf_section_data (sec)->u.opd_adjust = opd_adjust;
+ BFD_ASSERT (ppc64_elf_section_data (sec)->sec_type == sec_normal);
+ ppc64_elf_section_data (sec)->sec_type = sec_opd;
}
memset (opd_adjust, 0, amt);
@@ -8940,7 +8956,29 @@ group_sections (struct ppc_link_hash_tab
bfd_size_type stub_group_size,
bfd_boolean stubs_always_before_branch)
{
- asection **list = htab->input_list + htab->top_index;
+ asection **list;
+ bfd_size_type stub14_group_size;
+ bfd_boolean suppress_size_errors;
+
+ suppress_size_errors = FALSE;
+ stub14_group_size = stub_group_size;
+ if (stub_group_size == 1)
+ {
+ /* Default values. */
+ if (stubs_always_before_branch)
+ {
+ stub_group_size = 0x1e00000;
+ stub14_group_size = 0x7800;
+ }
+ else
+ {
+ stub_group_size = 0x1c00000;
+ stub14_group_size = 0x7000;
+ }
+ suppress_size_errors = TRUE;
+ }
+
+ list = htab->input_list + htab->top_index;
do
{
asection *tail = *list;
@@ -8954,15 +8992,17 @@ group_sections (struct ppc_link_hash_tab
curr = tail;
total = tail->size;
- big_sec = total > stub_group_size;
- if (big_sec)
+ big_sec = total > (ppc64_elf_section_data (tail)->has_14bit_branch
+ ? stub14_group_size : stub_group_size);
+ if (big_sec && !suppress_size_errors)
(*_bfd_error_handler) (_("%B section %A exceeds stub group size"),
tail->owner, tail);
curr_toc = htab->stub_group[tail->id].toc_off;
while ((prev = PREV_SEC (curr)) != NULL
&& ((total += curr->output_offset - prev->output_offset)
- < stub_group_size)
+ < (ppc64_elf_section_data (prev)->has_14bit_branch
+ ? stub14_group_size : stub_group_size))
&& htab->stub_group[prev->id].toc_off == curr_toc)
curr = prev;
@@ -8994,7 +9034,8 @@ group_sections (struct ppc_link_hash_tab
total = 0;
while (prev != NULL
&& ((total += tail->output_offset - prev->output_offset)
- < stub_group_size)
+ < (ppc64_elf_section_data (prev)->has_14bit_branch
+ ? stub14_group_size : stub_group_size))
&& htab->stub_group[prev->id].toc_off == curr_toc)
{
tail = prev;
@@ -9035,22 +9076,6 @@ ppc64_elf_size_stubs (bfd *output_bfd,
stub_group_size = -group_size;
else
stub_group_size = group_size;
- if (stub_group_size == 1)
- {
- /* Default values. */
- if (stubs_always_before_branch)
- {
- stub_group_size = 0x1e00000;
- if (htab->has_14bit_branch)
- stub_group_size = 0x7800;
- }
- else
- {
- stub_group_size = 0x1c00000;
- if (htab->has_14bit_branch)
- stub_group_size = 0x7000;
- }
- }
group_sections (htab, stub_group_size, stubs_always_before_branch);
@@ -9721,7 +9746,7 @@ ppc64_elf_relocate_section (bfd *output_
TOCstart = elf_gp (output_bfd);
symtab_hdr = &elf_tdata (input_bfd)->symtab_hdr;
sym_hashes = elf_sym_hashes (input_bfd);
- is_opd = ppc64_elf_section_data (input_section)->opd.adjust != NULL;
+ is_opd = ppc64_elf_section_data (input_section)->sec_type == sec_opd;
rel = relocs;
relend = relocs + input_section->reloc_count;
--
Alan Modra
IBM OzLabs - Linux Technology Centre
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