* [PATCH 1/3] bfd: aarch64: Refactor stub sizing code
@ 2023-03-21 14:28 Szabolcs Nagy
2023-03-22 13:28 ` Nick Clifton
0 siblings, 1 reply; 3+ messages in thread
From: Szabolcs Nagy @ 2023-03-21 14:28 UTC (permalink / raw)
To: binutils
elfNN_aarch64_size_stubs has grown big, so factor out the call stub
related code before adding new logic there.
---
bfd/elfnn-aarch64.c | 552 ++++++++++++++++++++++----------------------
1 file changed, 279 insertions(+), 273 deletions(-)
diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index bf8f913a66d..f858d10c596 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -4265,12 +4265,285 @@ _bfd_aarch64_erratum_843419_scan (bfd *input_bfd, asection *section,
}
-/* Determine and set the size of the stub section for a final link.
+/* Add stub entries for calls.
The basic idea here is to examine all the relocations looking for
PC-relative calls to a target that is unreachable with a "bl"
instruction. */
+static bool
+_bfd_aarch64_add_call_stub_entries (bool *stub_changed, bfd *output_bfd,
+ struct bfd_link_info *info)
+{
+ struct elf_aarch64_link_hash_table *htab = elf_aarch64_hash_table (info);
+ bfd *input_bfd;
+
+ for (input_bfd = info->input_bfds; input_bfd != NULL;
+ input_bfd = input_bfd->link.next)
+ {
+ Elf_Internal_Shdr *symtab_hdr;
+ asection *section;
+ Elf_Internal_Sym *local_syms = NULL;
+
+ if (!is_aarch64_elf (input_bfd)
+ || (input_bfd->flags & BFD_LINKER_CREATED) != 0)
+ continue;
+
+ /* We'll need the symbol table in a second. */
+ symtab_hdr = &elf_tdata (input_bfd)->symtab_hdr;
+ if (symtab_hdr->sh_info == 0)
+ continue;
+
+ /* Walk over each section attached to the input bfd. */
+ for (section = input_bfd->sections;
+ section != NULL; section = section->next)
+ {
+ Elf_Internal_Rela *internal_relocs, *irelaend, *irela;
+
+ /* If there aren't any relocs, then there's nothing more to do. */
+ if ((section->flags & SEC_RELOC) == 0
+ || section->reloc_count == 0
+ || (section->flags & SEC_CODE) == 0)
+ continue;
+
+ /* If this section is a link-once section that will be
+ discarded, then don't create any stubs. */
+ if (section->output_section == NULL
+ || section->output_section->owner != output_bfd)
+ continue;
+
+ /* Get the relocs. */
+ internal_relocs
+ = _bfd_elf_link_read_relocs (input_bfd, section, NULL,
+ NULL, info->keep_memory);
+ if (internal_relocs == NULL)
+ goto error_ret_free_local;
+
+ /* Now examine each relocation. */
+ irela = internal_relocs;
+ irelaend = irela + section->reloc_count;
+ for (; irela < irelaend; irela++)
+ {
+ unsigned int r_type, r_indx;
+ enum elf_aarch64_stub_type stub_type;
+ struct elf_aarch64_stub_hash_entry *stub_entry;
+ asection *sym_sec;
+ bfd_vma sym_value;
+ bfd_vma destination;
+ struct elf_aarch64_link_hash_entry *hash;
+ const char *sym_name;
+ char *stub_name;
+ const asection *id_sec;
+ unsigned char st_type;
+ bfd_size_type len;
+
+ r_type = ELFNN_R_TYPE (irela->r_info);
+ r_indx = ELFNN_R_SYM (irela->r_info);
+
+ if (r_type >= (unsigned int) R_AARCH64_end)
+ {
+ bfd_set_error (bfd_error_bad_value);
+ error_ret_free_internal:
+ if (elf_section_data (section)->relocs == NULL)
+ free (internal_relocs);
+ goto error_ret_free_local;
+ }
+
+ /* Only look for stubs on unconditional branch and
+ branch and link instructions. */
+ if (r_type != (unsigned int) AARCH64_R (CALL26)
+ && r_type != (unsigned int) AARCH64_R (JUMP26))
+ continue;
+
+ /* Now determine the call target, its name, value,
+ section. */
+ sym_sec = NULL;
+ sym_value = 0;
+ destination = 0;
+ hash = NULL;
+ sym_name = NULL;
+ if (r_indx < symtab_hdr->sh_info)
+ {
+ /* It's a local symbol. */
+ Elf_Internal_Sym *sym;
+ Elf_Internal_Shdr *hdr;
+
+ if (local_syms == NULL)
+ {
+ local_syms
+ = (Elf_Internal_Sym *) symtab_hdr->contents;
+ if (local_syms == NULL)
+ local_syms
+ = bfd_elf_get_elf_syms (input_bfd, symtab_hdr,
+ symtab_hdr->sh_info, 0,
+ NULL, NULL, NULL);
+ if (local_syms == NULL)
+ goto error_ret_free_internal;
+ }
+
+ sym = local_syms + r_indx;
+ hdr = elf_elfsections (input_bfd)[sym->st_shndx];
+ sym_sec = hdr->bfd_section;
+ if (!sym_sec)
+ /* This is an undefined symbol. It can never
+ be resolved. */
+ continue;
+
+ if (ELF_ST_TYPE (sym->st_info) != STT_SECTION)
+ sym_value = sym->st_value;
+ destination = (sym_value + irela->r_addend
+ + sym_sec->output_offset
+ + sym_sec->output_section->vma);
+ st_type = ELF_ST_TYPE (sym->st_info);
+ sym_name
+ = bfd_elf_string_from_elf_section (input_bfd,
+ symtab_hdr->sh_link,
+ sym->st_name);
+ }
+ else
+ {
+ int e_indx;
+
+ e_indx = r_indx - symtab_hdr->sh_info;
+ hash = ((struct elf_aarch64_link_hash_entry *)
+ elf_sym_hashes (input_bfd)[e_indx]);
+
+ while (hash->root.root.type == bfd_link_hash_indirect
+ || hash->root.root.type == bfd_link_hash_warning)
+ hash = ((struct elf_aarch64_link_hash_entry *)
+ hash->root.root.u.i.link);
+
+ if (hash->root.root.type == bfd_link_hash_defined
+ || hash->root.root.type == bfd_link_hash_defweak)
+ {
+ struct elf_aarch64_link_hash_table *globals =
+ elf_aarch64_hash_table (info);
+ sym_sec = hash->root.root.u.def.section;
+ sym_value = hash->root.root.u.def.value;
+ /* For a destination in a shared library,
+ use the PLT stub as target address to
+ decide whether a branch stub is
+ needed. */
+ if (globals->root.splt != NULL && hash != NULL
+ && hash->root.plt.offset != (bfd_vma) - 1)
+ {
+ sym_sec = globals->root.splt;
+ sym_value = hash->root.plt.offset;
+ if (sym_sec->output_section != NULL)
+ destination = (sym_value
+ + sym_sec->output_offset
+ + sym_sec->output_section->vma);
+ }
+ else if (sym_sec->output_section != NULL)
+ destination = (sym_value + irela->r_addend
+ + sym_sec->output_offset
+ + sym_sec->output_section->vma);
+ }
+ else if (hash->root.root.type == bfd_link_hash_undefined
+ || (hash->root.root.type
+ == bfd_link_hash_undefweak))
+ {
+ /* For a shared library, use the PLT stub as
+ target address to decide whether a long
+ branch stub is needed.
+ For absolute code, they cannot be handled. */
+ struct elf_aarch64_link_hash_table *globals =
+ elf_aarch64_hash_table (info);
+
+ if (globals->root.splt != NULL && hash != NULL
+ && hash->root.plt.offset != (bfd_vma) - 1)
+ {
+ sym_sec = globals->root.splt;
+ sym_value = hash->root.plt.offset;
+ if (sym_sec->output_section != NULL)
+ destination = (sym_value
+ + sym_sec->output_offset
+ + sym_sec->output_section->vma);
+ }
+ else
+ continue;
+ }
+ else
+ {
+ bfd_set_error (bfd_error_bad_value);
+ goto error_ret_free_internal;
+ }
+ st_type = ELF_ST_TYPE (hash->root.type);
+ sym_name = hash->root.root.root.string;
+ }
+
+ /* Determine what (if any) linker stub is needed. */
+ stub_type = aarch64_type_of_stub (section, irela, sym_sec,
+ st_type, destination);
+ if (stub_type == aarch64_stub_none)
+ continue;
+
+ /* Support for grouping stub sections. */
+ id_sec = htab->stub_group[section->id].link_sec;
+
+ /* Get the name of this stub. */
+ stub_name = elfNN_aarch64_stub_name (id_sec, sym_sec, hash,
+ irela);
+ if (!stub_name)
+ goto error_ret_free_internal;
+
+ stub_entry =
+ aarch64_stub_hash_lookup (&htab->stub_hash_table,
+ stub_name, false, false);
+ if (stub_entry != NULL)
+ {
+ /* The proper stub has already been created. */
+ free (stub_name);
+
+ /* Always update this stub's target since it may have
+ changed after layout. */
+ stub_entry->target_value = sym_value + irela->r_addend;
+ continue;
+ }
+
+ stub_entry = _bfd_aarch64_add_stub_entry_in_group
+ (stub_name, section, htab);
+ if (stub_entry == NULL)
+ {
+ free (stub_name);
+ goto error_ret_free_internal;
+ }
+
+ stub_entry->target_value = sym_value + irela->r_addend;
+ stub_entry->target_section = sym_sec;
+ stub_entry->stub_type = stub_type;
+ stub_entry->h = hash;
+ stub_entry->st_type = st_type;
+
+ if (sym_name == NULL)
+ sym_name = "unnamed";
+ len = sizeof (STUB_ENTRY_NAME) + strlen (sym_name);
+ stub_entry->output_name = bfd_alloc (htab->stub_bfd, len);
+ if (stub_entry->output_name == NULL)
+ {
+ free (stub_name);
+ goto error_ret_free_internal;
+ }
+
+ snprintf (stub_entry->output_name, len, STUB_ENTRY_NAME,
+ sym_name);
+
+ *stub_changed = true;
+ }
+
+ /* We're done with the internal relocs, free them. */
+ if (elf_section_data (section)->relocs == NULL)
+ free (internal_relocs);
+ }
+ }
+ return true;
+ error_ret_free_local:
+ return false;
+}
+
+
+/* Determine and set the size of the stub section for a final link. */
+
bool
elfNN_aarch64_size_stubs (bfd *output_bfd,
bfd *stub_bfd,
@@ -4282,7 +4555,6 @@ elfNN_aarch64_size_stubs (bfd *output_bfd,
{
bfd_size_type stub_group_size;
bool stubs_always_before_branch;
- bool stub_changed = false;
struct elf_aarch64_link_hash_table *htab = elf_aarch64_hash_table (info);
unsigned int num_erratum_835769_fixes = 0;
@@ -4357,285 +4629,19 @@ elfNN_aarch64_size_stubs (bfd *output_bfd,
(*htab->layout_sections_again) ();
}
- while (1)
+ for (;;)
{
- bfd *input_bfd;
-
- for (input_bfd = info->input_bfds;
- input_bfd != NULL; input_bfd = input_bfd->link.next)
- {
- Elf_Internal_Shdr *symtab_hdr;
- asection *section;
- Elf_Internal_Sym *local_syms = NULL;
-
- if (!is_aarch64_elf (input_bfd)
- || (input_bfd->flags & BFD_LINKER_CREATED) != 0)
- continue;
-
- /* We'll need the symbol table in a second. */
- symtab_hdr = &elf_tdata (input_bfd)->symtab_hdr;
- if (symtab_hdr->sh_info == 0)
- continue;
-
- /* Walk over each section attached to the input bfd. */
- for (section = input_bfd->sections;
- section != NULL; section = section->next)
- {
- Elf_Internal_Rela *internal_relocs, *irelaend, *irela;
-
- /* If there aren't any relocs, then there's nothing more
- to do. */
- if ((section->flags & SEC_RELOC) == 0
- || section->reloc_count == 0
- || (section->flags & SEC_CODE) == 0)
- continue;
-
- /* If this section is a link-once section that will be
- discarded, then don't create any stubs. */
- if (section->output_section == NULL
- || section->output_section->owner != output_bfd)
- continue;
-
- /* Get the relocs. */
- internal_relocs
- = _bfd_elf_link_read_relocs (input_bfd, section, NULL,
- NULL, info->keep_memory);
- if (internal_relocs == NULL)
- goto error_ret_free_local;
-
- /* Now examine each relocation. */
- irela = internal_relocs;
- irelaend = irela + section->reloc_count;
- for (; irela < irelaend; irela++)
- {
- unsigned int r_type, r_indx;
- enum elf_aarch64_stub_type stub_type;
- struct elf_aarch64_stub_hash_entry *stub_entry;
- asection *sym_sec;
- bfd_vma sym_value;
- bfd_vma destination;
- struct elf_aarch64_link_hash_entry *hash;
- const char *sym_name;
- char *stub_name;
- const asection *id_sec;
- unsigned char st_type;
- bfd_size_type len;
-
- r_type = ELFNN_R_TYPE (irela->r_info);
- r_indx = ELFNN_R_SYM (irela->r_info);
-
- if (r_type >= (unsigned int) R_AARCH64_end)
- {
- bfd_set_error (bfd_error_bad_value);
- error_ret_free_internal:
- if (elf_section_data (section)->relocs == NULL)
- free (internal_relocs);
- goto error_ret_free_local;
- }
-
- /* Only look for stubs on unconditional branch and
- branch and link instructions. */
- if (r_type != (unsigned int) AARCH64_R (CALL26)
- && r_type != (unsigned int) AARCH64_R (JUMP26))
- continue;
-
- /* Now determine the call target, its name, value,
- section. */
- sym_sec = NULL;
- sym_value = 0;
- destination = 0;
- hash = NULL;
- sym_name = NULL;
- if (r_indx < symtab_hdr->sh_info)
- {
- /* It's a local symbol. */
- Elf_Internal_Sym *sym;
- Elf_Internal_Shdr *hdr;
-
- if (local_syms == NULL)
- {
- local_syms
- = (Elf_Internal_Sym *) symtab_hdr->contents;
- if (local_syms == NULL)
- local_syms
- = bfd_elf_get_elf_syms (input_bfd, symtab_hdr,
- symtab_hdr->sh_info, 0,
- NULL, NULL, NULL);
- if (local_syms == NULL)
- goto error_ret_free_internal;
- }
-
- sym = local_syms + r_indx;
- hdr = elf_elfsections (input_bfd)[sym->st_shndx];
- sym_sec = hdr->bfd_section;
- if (!sym_sec)
- /* This is an undefined symbol. It can never
- be resolved. */
- continue;
-
- if (ELF_ST_TYPE (sym->st_info) != STT_SECTION)
- sym_value = sym->st_value;
- destination = (sym_value + irela->r_addend
- + sym_sec->output_offset
- + sym_sec->output_section->vma);
- st_type = ELF_ST_TYPE (sym->st_info);
- sym_name
- = bfd_elf_string_from_elf_section (input_bfd,
- symtab_hdr->sh_link,
- sym->st_name);
- }
- else
- {
- int e_indx;
+ bool stub_changed = false;
- e_indx = r_indx - symtab_hdr->sh_info;
- hash = ((struct elf_aarch64_link_hash_entry *)
- elf_sym_hashes (input_bfd)[e_indx]);
-
- while (hash->root.root.type == bfd_link_hash_indirect
- || hash->root.root.type == bfd_link_hash_warning)
- hash = ((struct elf_aarch64_link_hash_entry *)
- hash->root.root.u.i.link);
-
- if (hash->root.root.type == bfd_link_hash_defined
- || hash->root.root.type == bfd_link_hash_defweak)
- {
- struct elf_aarch64_link_hash_table *globals =
- elf_aarch64_hash_table (info);
- sym_sec = hash->root.root.u.def.section;
- sym_value = hash->root.root.u.def.value;
- /* For a destination in a shared library,
- use the PLT stub as target address to
- decide whether a branch stub is
- needed. */
- if (globals->root.splt != NULL && hash != NULL
- && hash->root.plt.offset != (bfd_vma) - 1)
- {
- sym_sec = globals->root.splt;
- sym_value = hash->root.plt.offset;
- if (sym_sec->output_section != NULL)
- destination = (sym_value
- + sym_sec->output_offset
- +
- sym_sec->output_section->vma);
- }
- else if (sym_sec->output_section != NULL)
- destination = (sym_value + irela->r_addend
- + sym_sec->output_offset
- + sym_sec->output_section->vma);
- }
- else if (hash->root.root.type == bfd_link_hash_undefined
- || (hash->root.root.type
- == bfd_link_hash_undefweak))
- {
- /* For a shared library, use the PLT stub as
- target address to decide whether a long
- branch stub is needed.
- For absolute code, they cannot be handled. */
- struct elf_aarch64_link_hash_table *globals =
- elf_aarch64_hash_table (info);
-
- if (globals->root.splt != NULL && hash != NULL
- && hash->root.plt.offset != (bfd_vma) - 1)
- {
- sym_sec = globals->root.splt;
- sym_value = hash->root.plt.offset;
- if (sym_sec->output_section != NULL)
- destination = (sym_value
- + sym_sec->output_offset
- +
- sym_sec->output_section->vma);
- }
- else
- continue;
- }
- else
- {
- bfd_set_error (bfd_error_bad_value);
- goto error_ret_free_internal;
- }
- st_type = ELF_ST_TYPE (hash->root.type);
- sym_name = hash->root.root.root.string;
- }
-
- /* Determine what (if any) linker stub is needed. */
- stub_type = aarch64_type_of_stub (section, irela, sym_sec,
- st_type, destination);
- if (stub_type == aarch64_stub_none)
- continue;
-
- /* Support for grouping stub sections. */
- id_sec = htab->stub_group[section->id].link_sec;
-
- /* Get the name of this stub. */
- stub_name = elfNN_aarch64_stub_name (id_sec, sym_sec, hash,
- irela);
- if (!stub_name)
- goto error_ret_free_internal;
-
- stub_entry =
- aarch64_stub_hash_lookup (&htab->stub_hash_table,
- stub_name, false, false);
- if (stub_entry != NULL)
- {
- /* The proper stub has already been created. */
- free (stub_name);
- /* Always update this stub's target since it may have
- changed after layout. */
- stub_entry->target_value = sym_value + irela->r_addend;
- continue;
- }
-
- stub_entry = _bfd_aarch64_add_stub_entry_in_group
- (stub_name, section, htab);
- if (stub_entry == NULL)
- {
- free (stub_name);
- goto error_ret_free_internal;
- }
-
- stub_entry->target_value = sym_value + irela->r_addend;
- stub_entry->target_section = sym_sec;
- stub_entry->stub_type = stub_type;
- stub_entry->h = hash;
- stub_entry->st_type = st_type;
-
- if (sym_name == NULL)
- sym_name = "unnamed";
- len = sizeof (STUB_ENTRY_NAME) + strlen (sym_name);
- stub_entry->output_name = bfd_alloc (htab->stub_bfd, len);
- if (stub_entry->output_name == NULL)
- {
- free (stub_name);
- goto error_ret_free_internal;
- }
-
- snprintf (stub_entry->output_name, len, STUB_ENTRY_NAME,
- sym_name);
-
- stub_changed = true;
- }
-
- /* We're done with the internal relocs, free them. */
- if (elf_section_data (section)->relocs == NULL)
- free (internal_relocs);
- }
- }
+ if (!_bfd_aarch64_add_call_stub_entries (&stub_changed, output_bfd, info))
+ return false;
if (!stub_changed)
- break;
+ return true;
_bfd_aarch64_resize_stubs (htab);
-
- /* Ask the linker to do its stuff. */
(*htab->layout_sections_again) ();
- stub_changed = false;
}
-
- return true;
-
- error_ret_free_local:
- return false;
}
/* Build all the stubs associated with the current output file. The
--
2.25.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 1/3] bfd: aarch64: Refactor stub sizing code
2023-03-21 14:28 [PATCH 1/3] bfd: aarch64: Refactor stub sizing code Szabolcs Nagy
@ 2023-03-22 13:28 ` Nick Clifton
2023-03-22 13:40 ` Szabolcs Nagy
0 siblings, 1 reply; 3+ messages in thread
From: Nick Clifton @ 2023-03-22 13:28 UTC (permalink / raw)
To: Szabolcs Nagy, binutils
Hi Szabolcs,
> elfNN_aarch64_size_stubs has grown big, so factor out the call stub
> related code before adding new logic there.
> ---
> bfd/elfnn-aarch64.c | 552 ++++++++++++++++++++++----------------------
> 1 file changed, 279 insertions(+), 273 deletions(-)
Patch approved - please apply.
Quick question:
> - while (1)
> + for (;;)
Is there any particular reason for this specific change ?
Cheers
Nick
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 1/3] bfd: aarch64: Refactor stub sizing code
2023-03-22 13:28 ` Nick Clifton
@ 2023-03-22 13:40 ` Szabolcs Nagy
0 siblings, 0 replies; 3+ messages in thread
From: Szabolcs Nagy @ 2023-03-22 13:40 UTC (permalink / raw)
To: Nick Clifton, binutils
The 03/22/2023 13:28, Nick Clifton wrote:
> Hi Szabolcs,
>
> > elfNN_aarch64_size_stubs has grown big, so factor out the call stub
> > related code before adding new logic there.
> > ---
> > bfd/elfnn-aarch64.c | 552 ++++++++++++++++++++++----------------------
> > 1 file changed, 279 insertions(+), 273 deletions(-)
>
> Patch approved - please apply.
>
> Quick question:
>
> > - while (1)
> > + for (;;)
>
> Is there any particular reason for this specific change ?
no reason
i probably lost the original context when i rewrote that loop
i can keep the while if needed.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-03-21 14:28 [PATCH 1/3] bfd: aarch64: Refactor stub sizing code Szabolcs Nagy
2023-03-22 13:28 ` Nick Clifton
2023-03-22 13:40 ` Szabolcs Nagy
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