This is the mail archive of the
binutils@sourceware.org
mailing list for the binutils project.
Re: [PATCH, binutils, ARM 6/11] Support for dedicated output section for some veneer types
- From: Thomas Preudhomme <thomas dot preudhomme at foss dot arm dot com>
- To: binutils at sourceware dot org
- Date: Thu, 05 May 2016 11:26:31 +0100
- Subject: Re: [PATCH, binutils, ARM 6/11] Support for dedicated output section for some veneer types
- Authentication-results: sourceware.org; auth=none
- References: <1484704 dot KMyP2r4qul at e108577-lin>
On Tuesday 29 March 2016 15:39:25 Thomas Preudhomme wrote:
> Hi,
>
> This patch is part of a patch series to add support for ARMv8-M Security
> Extensions[1] to GNU ld. This specific patch adds support for having veneers
> of a given type in a dedicated output section.
>
> ARM v8-M Security Extensions require [3] secure gateway veneers to be
> generated for (secure) entry function in order for code to transition from
> non-secure state to secure state when calling these entry function. One
> requirement for these veneers [4] is to be able to keep their addresses when
> the secure code is relinked in order to avoid relinking the non secure code
> with the secure code. This patch adds support for generating these veneers
> in a dedicated output section and expect the user to specify the address of
> that section (either via --section-start parameter or in the linker
> script). This ensure that they are placed in a memory area with sufficient
> space for more veneers to be added. Ensuring that existing veneers keep
> their addresses when the secure executable is relinked is handled by a
> subsequent patch of this patch series.
>
>
> [1] Software requirements for ARMv8-M Security Extension are described in
> document ARM-ECM-0359818 [2]
> [2] Available on http://infocenter.arm.com in Developer guides and articles
> > Software development > ARMÂv8-M Security Extensions: Requirements on
> Development Tools
> [3] See section 3.4.3 and requirement 44 of ARM-ECM-0359818 [2]
> [4] requirement 14 and following comment of ARM-ECM-0359818 [2]
Please find an updated version without the switch case for the
arm_dedicated_stub_* functions.
ChangeLog entries are unchanged:
*** bfd/ChangeLog ***
2016-02-17 Thomas Preud'homme <thomas.preudhomme@arm.com>
* bfd-in.h (bfd_elf32_arm_keep_private_stub_output_sections): Declare
bfd hook.
* bfd-in2.h: Regenerate.
* elf32-arm.c (arm_dedicated_stub_output_section_required): New
function.
(arm_dedicated_stub_output_section_required_alignment): Likewise.
(arm_dedicated_stub_output_section_name): Likewise.
(arm_dedicated_stub_input_section_ptr): Likewise.
(elf32_arm_create_or_find_stub_sec): Add stub type parameter and
function description comment. Add support for dedicated output stub
section to given stub types.
(elf32_arm_add_stub): Add a stub type parameter and pass it down to
elf32_arm_create_or_find_stub_sec.
(elf32_arm_create_stub): Pass stub type down to elf32_arm_add_stub.
(elf32_arm_size_stubs): Pass stub type when calling
elf32_arm_create_or_find_stub_sec for Cortex-A8 erratum veneers.
(bfd_elf32_arm_keep_private_stub_output_sections): New function.
*** ld/ChangeLog ***
2016-01-04 Thomas Preud'homme <thomas.preudhomme@arm.com>
* emultempl/armelf.em (arm_elf_before_allocation): Call
bfd_elf32_arm_keep_private_stub_output_sections before generic
before_allocation function.
diff --git a/bfd/bfd-in.h b/bfd/bfd-in.h
index
571a63672bfda3b4310adf791fb28cf23ae09ae0..c66ce3bba1ad1d1ce670f7404e465834cbf43fb1
100644
--- a/bfd/bfd-in.h
+++ b/bfd/bfd-in.h
@@ -903,6 +903,9 @@ extern bfd_boolean bfd_elf32_arm_get_bfd_for_interworking
extern bfd_boolean bfd_elf32_arm_add_glue_sections_to_bfd
(bfd *, struct bfd_link_info *);
+extern void bfd_elf32_arm_keep_private_stub_output_sections
+ (struct bfd_link_info *);
+
/* ELF ARM mapping symbol support. */
#define BFD_ARM_SPECIAL_SYM_TYPE_MAP (1 << 0)
#define BFD_ARM_SPECIAL_SYM_TYPE_TAG (1 << 1)
diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index
294da5e1c163bd443c73a99778880a986a08566b..afaca4ef19e49cf9899952a84a90c60fcd3fc8dd
100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -910,6 +910,9 @@ extern bfd_boolean bfd_elf32_arm_get_bfd_for_interworking
extern bfd_boolean bfd_elf32_arm_add_glue_sections_to_bfd
(bfd *, struct bfd_link_info *);
+extern void bfd_elf32_arm_keep_private_stub_output_sections
+ (struct bfd_link_info *);
+
/* ELF ARM mapping symbol support. */
#define BFD_ARM_SPECIAL_SYM_TYPE_MAP (1 << 0)
#define BFD_ARM_SPECIAL_SYM_TYPE_TAG (1 << 1)
diff --git a/bfd/elf32-arm.c b/bfd/elf32-arm.c
index
02977358ac69deab379f2d826c44bfc5efa49e1a..ab878b20905c907b3496317c7ed1c9c698d850c9
100644
--- a/bfd/elf32-arm.c
+++ b/bfd/elf32-arm.c
@@ -4136,68 +4136,155 @@ elf32_arm_get_stub_entry (const asection
*input_section,
return stub_entry;
}
-/* Find or create a stub section. Returns a pointer to the stub section, and
- the section to which the stub section will be attached (in *LINK_SEC_P).
+/* Whether veneers of type STUB_TYPE require to be in a dedicated output
+ section. */
+
+static bfd_boolean
+arm_dedicated_stub_output_section_required (enum elf32_arm_stub_type
stub_type)
+{
+ if (stub_type >= max_stub_type)
+ abort (); /* Should be unreachable. */
+
+ return FALSE;
+}
+
+/* Required alignment (as a power of 2) for the dedicated section holding
+ veneers of type STUB_TYPE, or 0 if veneers of this type are interspersed
+ with input sections. */
+
+static int
+arm_dedicated_stub_output_section_required_alignment
+ (enum elf32_arm_stub_type stub_type)
+{
+ if (stub_type >= max_stub_type)
+ abort (); /* Should be unreachable. */
+
+ BFD_ASSERT (!arm_dedicated_stub_output_section_required (stub_type));
+ return 0;
+}
+
+/* Name of the dedicated output section to put veneers of type STUB_TYPE, or
+ NULL if veneers of this type are interspersed with input sections. */
+
+static const char *
+arm_dedicated_stub_output_section_name (enum elf32_arm_stub_type stub_type)
+{
+ if (stub_type >= max_stub_type)
+ abort (); /* Should be unreachable. */
+
+ BFD_ASSERT (!arm_dedicated_stub_output_section_required (stub_type));
+ return NULL;
+}
+
+/* If veneers of type STUB_TYPE should go in a dedicated output section,
+ returns the address of the hash table field in HTAB holding a pointer to
the
+ corresponding input section. Otherwise, returns NULL. */
+
+static asection **
+arm_dedicated_stub_input_section_ptr
+ (struct elf32_arm_link_hash_table *htab ATTRIBUTE_UNUSED,
+ enum elf32_arm_stub_type stub_type)
+{
+ if (stub_type >= max_stub_type)
+ abort (); /* Should be unreachable. */
+
+ BFD_ASSERT (!arm_dedicated_stub_output_section_required (stub_type));
+ return NULL;
+}
+
+/* Find or create a stub section to contain a stub of type STUB_TYPE.
SECTION
+ is the section that branch into veneer and can be NULL if stub should go
in
+ a dedicated output section. Returns a pointer to the stub section, and
the
+ section to which the stub section will be attached (in *LINK_SEC_P).
LINK_SEC_P may be NULL. */
static asection *
elf32_arm_create_or_find_stub_sec (asection **link_sec_p, asection *section,
- struct elf32_arm_link_hash_table *htab)
+ struct elf32_arm_link_hash_table *htab,
+ enum elf32_arm_stub_type stub_type)
{
- asection *link_sec;
- asection *stub_sec;
- asection *out_sec;
-
- link_sec = htab->stub_group[section->id].link_sec;
- BFD_ASSERT (link_sec != NULL);
- stub_sec = htab->stub_group[section->id].stub_sec;
+ asection *link_sec, *out_sec, **stub_sec_p;
+ const char *stub_sec_prefix;
+ bfd_boolean dedicated_output_section =
+ arm_dedicated_stub_output_section_required (stub_type);
+ int align;
- if (stub_sec == NULL)
+ if (dedicated_output_section)
{
- stub_sec = htab->stub_group[link_sec->id].stub_sec;
- if (stub_sec == NULL)
+ bfd *output_bfd = htab->obfd;
+ const char *out_sec_name =
+ arm_dedicated_stub_output_section_name (stub_type);
+ link_sec = NULL;
+ stub_sec_p = arm_dedicated_stub_input_section_ptr (htab, stub_type);
+ stub_sec_prefix = out_sec_name;
+ align = arm_dedicated_stub_output_section_required_alignment
(stub_type);
+ out_sec = bfd_get_section_by_name (output_bfd, out_sec_name);
+ if (out_sec == NULL)
{
- size_t namelen;
- bfd_size_type len;
- char *s_name;
-
- namelen = strlen (link_sec->name);
- len = namelen + sizeof (STUB_SUFFIX);
- s_name = (char *) bfd_alloc (htab->stub_bfd, len);
- if (s_name == NULL)
- return NULL;
-
- memcpy (s_name, link_sec->name, namelen);
- memcpy (s_name + namelen, STUB_SUFFIX, sizeof (STUB_SUFFIX));
- out_sec = link_sec->output_section;
- stub_sec = (*htab->add_stub_section) (s_name, out_sec, link_sec,
- htab->nacl_p ? 4 : 3);
- if (stub_sec == NULL)
- return NULL;
- htab->stub_group[link_sec->id].stub_sec = stub_sec;
+ (*_bfd_error_handler) (_("No address assigned to the veneers output "
+ "section %s"), out_sec_name);
+ return NULL;
}
- htab->stub_group[section->id].stub_sec = stub_sec;
}
+ else
+ {
+ link_sec = htab->stub_group[section->id].link_sec;
+ BFD_ASSERT (link_sec != NULL);
+ stub_sec_p = &htab->stub_group[section->id].stub_sec;
+ if (*stub_sec_p == NULL)
+ stub_sec_p = &htab->stub_group[link_sec->id].stub_sec;
+ stub_sec_prefix = link_sec->name;
+ out_sec = link_sec->output_section;
+ align = htab->nacl_p ? 4 : 3;
+ }
+
+ if (*stub_sec_p == NULL)
+ {
+ size_t namelen;
+ bfd_size_type len;
+ char *s_name;
+
+ namelen = strlen (stub_sec_prefix);
+ len = namelen + sizeof (STUB_SUFFIX);
+ s_name = (char *) bfd_alloc (htab->stub_bfd, len);
+ if (s_name == NULL)
+ return NULL;
+
+ memcpy (s_name, stub_sec_prefix, namelen);
+ memcpy (s_name + namelen, STUB_SUFFIX, sizeof (STUB_SUFFIX));
+ *stub_sec_p = (*htab->add_stub_section) (s_name, out_sec, link_sec,
+ align);
+ if (*stub_sec_p == NULL)
+ return NULL;
+
+ out_sec->flags |= SEC_ALLOC | SEC_LOAD | SEC_READONLY | SEC_CODE
+ | SEC_HAS_CONTENTS | SEC_RELOC | SEC_IN_MEMORY
+ | SEC_KEEP;
+ }
+
+ if (!dedicated_output_section)
+ htab->stub_group[section->id].stub_sec = *stub_sec_p;
if (link_sec_p)
*link_sec_p = link_sec;
- return stub_sec;
+ return *stub_sec_p;
}
/* Add a new stub entry to the stub hash. Not all fields of the new
stub entry are initialised. */
static struct elf32_arm_stub_hash_entry *
-elf32_arm_add_stub (const char *stub_name,
- asection *section,
- struct elf32_arm_link_hash_table *htab)
+elf32_arm_add_stub (const char *stub_name, asection *section,
+ struct elf32_arm_link_hash_table *htab,
+ enum elf32_arm_stub_type stub_type)
{
asection *link_sec;
asection *stub_sec;
struct elf32_arm_stub_hash_entry *stub_entry;
- stub_sec = elf32_arm_create_or_find_stub_sec (&link_sec, section, htab);
+ stub_sec = elf32_arm_create_or_find_stub_sec (&link_sec, section, htab,
+ stub_type);
if (stub_sec == NULL)
return NULL;
@@ -5187,7 +5274,7 @@ elf32_arm_create_stub (struct elf32_arm_link_hash_table
*htab,
return TRUE;
}
- stub_entry = elf32_arm_add_stub (stub_name, section, htab);
+ stub_entry = elf32_arm_add_stub (stub_name, section, htab, stub_type);
if (stub_entry == NULL)
{
if (!sym_claimed)
@@ -5685,7 +5772,7 @@ elf32_arm_size_stubs (bfd *output_bfd,
for (i = 0; i < num_a8_fixes; i++)
{
stub_sec = elf32_arm_create_or_find_stub_sec (NULL,
- a8_fixes[i].section, htab);
+ a8_fixes[i].section, htab, a8_fixes[i].stub_type);
if (stub_sec == NULL)
goto error_ret_free_local;
@@ -6479,6 +6566,37 @@ bfd_elf32_arm_add_glue_sections_to_bfd (bfd *abfd,
&& arm_make_glue_section (abfd, STM32L4XX_ERRATUM_VENEER_SECTION_NAME);
}
+/* Mark output sections of veneers needing a dedicated one with SEC_KEEP.
This
+ ensures they are not marked for deletion by
+ strip_excluded_output_sections () when veneers are going to be created
+ later. Not doing so would trigger assert on empty section size in
+ lang_size_sections_1 (). */
+
+void
+bfd_elf32_arm_keep_private_stub_output_sections (struct bfd_link_info *info)
+{
+ enum elf32_arm_stub_type stub_type;
+
+ /* If we are only performing a partial
+ link do not bother adding the glue. */
+ if (bfd_link_relocatable (info))
+ return;
+
+ for (stub_type = arm_stub_none + 1; stub_type < max_stub_type; stub_type++)
+ {
+ asection *out_sec;
+ const char *out_sec_name;
+
+ if (!arm_dedicated_stub_output_section_required (stub_type))
+ continue;
+
+ out_sec_name = arm_dedicated_stub_output_section_name (stub_type);
+ out_sec = bfd_get_section_by_name (info->output_bfd, out_sec_name);
+ if (out_sec != NULL)
+ out_sec->flags |= SEC_KEEP;
+ }
+}
+
/* Select a BFD to be used to hold the sections used by the glue code.
This function is called from the linker scripts in ld/emultempl/
{armelf/pe}.em. */
diff --git a/ld/emultempl/armelf.em b/ld/emultempl/armelf.em
index
caa2fbfff3633f2a7f69a7b197574eed8279d6c4..6074824f72d6f607449000702e7c5945bfe412ef
100644
--- a/ld/emultempl/armelf.em
+++ b/ld/emultempl/armelf.em
@@ -83,6 +83,10 @@ arm_elf_before_allocation (void)
/* Auto-select Cortex-A8 erratum fix if it wasn't explicitly specified. */
bfd_elf32_arm_set_cortex_a8_fix (link_info.output_bfd, &link_info);
+ /* Ensure the output sections of veneers needing a dedicated one is not
+ removed. */
+ bfd_elf32_arm_keep_private_stub_output_sections (&link_info);
+
/* We should be able to set the size of the interworking stub section. We
can't do it until later if we have dynamic sections, though. */
if (elf_hash_table (&link_info)->dynobj == NULL)
Best regards,
Thomas