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TLS orphan section placement
- From: Alan Modra <amodra at gmail dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: Binutils <binutils at sourceware dot org>
- Date: Fri, 24 Jan 2014 23:23:57 +1030
- Subject: TLS orphan section placement
- Authentication-results: sourceware.org; auth=none
- References: <20140122193013 dot GA4156 at intel dot com> <20140123035510 dot GZ5390 at bubble dot grove dot modra dot org> <CAMe9rOq6KvUnsrzQTEBE9XzHM8DKC4UaWqLet_NgReVE0kCT-A at mail dot gmail dot com>
On Wed, Jan 22, 2014 at 08:19:31PM -0800, H.J. Lu wrote:
> On Wed, Jan 22, 2014 at 7:55 PM, Alan Modra <amodra@gmail.com> wrote:
> > On Wed, Jan 22, 2014 at 11:30:13AM -0800, H.J. Lu wrote:
> >> PR ld/16498
> >> * elf.c (_bfd_elf_map_sections_to_segments): Issue a linker error
> >> if TLS sections are not adjacent.
> >
> > This part is OK.
>
> I'd like to augment my patch like
Yes, this is OK too.
> > On the other hand, the testcase is really showing a fault in orphan
> > section handling. If ld was a little more clever, it would put .tbss
> > after .tdata and your testcase would no longer give an error.
> >
>
> I am enclosing a simple patch which does it. However, it
> doesn't solve the second testcase in the bug report since
> it has a linker script:
>
> ---
> SECTIONS
> {
> tls_data_init : { *(.tdata .tdata.* .gnu.linkonce.td.*) }
> .data :
> {
> *(.data .data.* .gnu.linkonce.d.*)
> }
> /DISCARD/ : { *(.note.GNU-stack) *(.gnu_debuglink) *(.gnu.lto_*) }
> }
> ---
Besides the place_orphan change you posted, which is OK to commit,
you need something like the following.
Ensures TLS orphans are placed adjacent to existing TLS sections,
and fixes places where the output_section_statement flags (which might
not be set) were tested when bfd_section flags were available.
* ldlang.c (lang_output_section_find_by_flags): Be careful to
test look->bfd_section->flags if available rather than
look->flags. Separate SEC_THREAD_LOCAL handling from
SEC_READONLY loop, and rewrite.
diff --git a/ld/ldlang.c b/ld/ldlang.c
index 1a0d48f..9903f70 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -1495,7 +1495,7 @@ lang_output_section_find_by_flags (const asection *sec,
lang_match_sec_type_func match_type)
{
lang_output_section_statement_type *first, *look, *found;
- flagword flags;
+ flagword look_flags, sec_flags, differ;
/* We know the first statement on this list is *ABS*. May as well
skip it. */
@@ -1503,21 +1503,22 @@ lang_output_section_find_by_flags (const asection *sec,
first = first->next;
/* First try for an exact match. */
+ sec_flags = sec->flags;
found = NULL;
for (look = first; look; look = look->next)
{
- flags = look->flags;
+ look_flags = look->flags;
if (look->bfd_section != NULL)
{
- flags = look->bfd_section->flags;
+ look_flags = look->bfd_section->flags;
if (match_type && !match_type (link_info.output_bfd,
look->bfd_section,
sec->owner, sec))
continue;
}
- flags ^= sec->flags;
- if (!(flags & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD | SEC_READONLY
- | SEC_CODE | SEC_SMALL_DATA | SEC_THREAD_LOCAL)))
+ differ = look_flags ^ sec_flags;
+ if (!(differ & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD | SEC_READONLY
+ | SEC_CODE | SEC_SMALL_DATA | SEC_THREAD_LOCAL)))
found = look;
}
if (found != NULL)
@@ -1527,115 +1528,144 @@ lang_output_section_find_by_flags (const asection *sec,
return found;
}
- if ((sec->flags & SEC_CODE) != 0
- && (sec->flags & SEC_ALLOC) != 0)
+ if ((sec_flags & SEC_CODE) != 0
+ && (sec_flags & SEC_ALLOC) != 0)
{
/* Try for a rw code section. */
for (look = first; look; look = look->next)
{
- flags = look->flags;
+ look_flags = look->flags;
if (look->bfd_section != NULL)
{
- flags = look->bfd_section->flags;
+ look_flags = look->bfd_section->flags;
if (match_type && !match_type (link_info.output_bfd,
look->bfd_section,
sec->owner, sec))
continue;
}
- flags ^= sec->flags;
- if (!(flags & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD
- | SEC_CODE | SEC_SMALL_DATA | SEC_THREAD_LOCAL)))
+ differ = look_flags ^ sec_flags;
+ if (!(differ & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD
+ | SEC_CODE | SEC_SMALL_DATA | SEC_THREAD_LOCAL)))
found = look;
}
}
- else if ((sec->flags & (SEC_READONLY | SEC_THREAD_LOCAL)) != 0
- && (sec->flags & SEC_ALLOC) != 0)
+ else if ((sec_flags & SEC_READONLY) != 0
+ && (sec_flags & SEC_ALLOC) != 0)
{
/* .rodata can go after .text, .sdata2 after .rodata. */
for (look = first; look; look = look->next)
{
- flags = look->flags;
+ look_flags = look->flags;
if (look->bfd_section != NULL)
{
- flags = look->bfd_section->flags;
+ look_flags = look->bfd_section->flags;
if (match_type && !match_type (link_info.output_bfd,
look->bfd_section,
sec->owner, sec))
continue;
}
- flags ^= sec->flags;
- if (!(flags & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD
- | SEC_READONLY | SEC_SMALL_DATA))
- || (!(flags & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD
- | SEC_READONLY))
- && !(look->flags & SEC_SMALL_DATA))
- || (!(flags & (SEC_THREAD_LOCAL | SEC_ALLOC))
- && (look->flags & SEC_THREAD_LOCAL)
- && (!(flags & SEC_LOAD)
- || (look->flags & SEC_LOAD))))
+ differ = look_flags ^ sec_flags;
+ if (!(differ & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD
+ | SEC_READONLY | SEC_SMALL_DATA))
+ || (!(differ & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD
+ | SEC_READONLY))
+ && !(look_flags & SEC_SMALL_DATA)))
found = look;
}
}
- else if ((sec->flags & SEC_SMALL_DATA) != 0
- && (sec->flags & SEC_ALLOC) != 0)
+ else if ((sec_flags & SEC_THREAD_LOCAL) != 0
+ && (sec_flags & SEC_ALLOC) != 0)
+ {
+ /* .tdata can go after .data, .tbss after .tdata. Treat .tbss
+ as if it were a loaded section, and don't use match_type. */
+ bfd_boolean seen_thread_local = FALSE;
+
+ match_type = NULL;
+ for (look = first; look; look = look->next)
+ {
+ look_flags = look->flags;
+ if (look->bfd_section != NULL)
+ look_flags = look->bfd_section->flags;
+
+ differ = look_flags ^ (sec_flags | SEC_LOAD | SEC_HAS_CONTENTS);
+ if (!(differ & (SEC_THREAD_LOCAL | SEC_ALLOC)))
+ {
+ /* .tdata and .tbss must be adjacent and in that order. */
+ if (!(look_flags & SEC_LOAD)
+ && (sec_flags & SEC_LOAD))
+ /* ..so if we're at a .tbss section and we're placing
+ a .tdata section stop looking and return the
+ previous section. */
+ break;
+ found = look;
+ seen_thread_local = TRUE;
+ }
+ else if (seen_thread_local)
+ break;
+ else if (!(differ & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD)))
+ found = look;
+ }
+ }
+ else if ((sec_flags & SEC_SMALL_DATA) != 0
+ && (sec_flags & SEC_ALLOC) != 0)
{
/* .sdata goes after .data, .sbss after .sdata. */
for (look = first; look; look = look->next)
{
- flags = look->flags;
+ look_flags = look->flags;
if (look->bfd_section != NULL)
{
- flags = look->bfd_section->flags;
+ look_flags = look->bfd_section->flags;
if (match_type && !match_type (link_info.output_bfd,
look->bfd_section,
sec->owner, sec))
continue;
}
- flags ^= sec->flags;
- if (!(flags & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD
- | SEC_THREAD_LOCAL))
- || ((look->flags & SEC_SMALL_DATA)
- && !(sec->flags & SEC_HAS_CONTENTS)))
+ differ = look_flags ^ sec_flags;
+ if (!(differ & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD
+ | SEC_THREAD_LOCAL))
+ || ((look_flags & SEC_SMALL_DATA)
+ && !(sec_flags & SEC_HAS_CONTENTS)))
found = look;
}
}
- else if ((sec->flags & SEC_HAS_CONTENTS) != 0
- && (sec->flags & SEC_ALLOC) != 0)
+ else if ((sec_flags & SEC_HAS_CONTENTS) != 0
+ && (sec_flags & SEC_ALLOC) != 0)
{
/* .data goes after .rodata. */
for (look = first; look; look = look->next)
{
- flags = look->flags;
+ look_flags = look->flags;
if (look->bfd_section != NULL)
{
- flags = look->bfd_section->flags;
+ look_flags = look->bfd_section->flags;
if (match_type && !match_type (link_info.output_bfd,
look->bfd_section,
sec->owner, sec))
continue;
}
- flags ^= sec->flags;
- if (!(flags & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD
- | SEC_SMALL_DATA | SEC_THREAD_LOCAL)))
+ differ = look_flags ^ sec_flags;
+ if (!(differ & (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD
+ | SEC_SMALL_DATA | SEC_THREAD_LOCAL)))
found = look;
}
}
- else if ((sec->flags & SEC_ALLOC) != 0)
+ else if ((sec_flags & SEC_ALLOC) != 0)
{
/* .bss goes after any other alloc section. */
for (look = first; look; look = look->next)
{
- flags = look->flags;
+ look_flags = look->flags;
if (look->bfd_section != NULL)
{
- flags = look->bfd_section->flags;
+ look_flags = look->bfd_section->flags;
if (match_type && !match_type (link_info.output_bfd,
look->bfd_section,
sec->owner, sec))
continue;
}
- flags ^= sec->flags;
- if (!(flags & SEC_ALLOC))
+ differ = look_flags ^ sec_flags;
+ if (!(differ & SEC_ALLOC))
found = look;
}
}
@@ -1644,11 +1674,11 @@ lang_output_section_find_by_flags (const asection *sec,
/* non-alloc go last. */
for (look = first; look; look = look->next)
{
- flags = look->flags;
+ look_flags = look->flags;
if (look->bfd_section != NULL)
- flags = look->bfd_section->flags;
- flags ^= sec->flags;
- if (!(flags & SEC_DEBUGGING))
+ look_flags = look->bfd_section->flags;
+ differ = look_flags ^ sec_flags;
+ if (!(differ & SEC_DEBUGGING))
found = look;
}
return found;
--
Alan Modra
Australia Development Lab, IBM