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Re: [PATCH 1/3] ELF: Group PT_NOTE segments by section alignments
On Wed, Oct 3, 2018 at 3:30 AM Nick Clifton <nickc@redhat.com> wrote:
>
> Hi H.J.
>
> One question:
>
> > + while (s->next != NULL
> > + && s->next->alignment_power == alignment_power
> > + && (s->next->flags & SEC_LOAD) != 0
> > + && CONST_STRNEQ (s->next->name, ".note"))
> > + s = s->next;
>
> I did not think that note sections were required to have a ".note"
> prefix to their name. So wouldn't it be better to check for a SHF_NOTE
> flag instead ? (Assuming that the section is in an ELF format bfd, of
> course).
>
> I appreciate that the code that you are patching also used the CONST_STRNEQ
> check, but I am thinking that now would be a good time to fix this bug
> as well. If the section is not in an ELF format file, you could always
> fall back on checking for the .note prefix.
get_program_header_size and _bfd_elf_map_sections_to_segments are only
used on ELF files. This updated patch checks SHT_NOTE section type instead.
OK for master?
Thanks.
--
H.J.
From a382938cff5369b8ed32544899a0f8adb23b1310 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Tue, 18 Sep 2018 05:54:56 -0700
Subject: [PATCH] ELF: Group PT_NOTE segments by section alignments
Alignments of SHT_NOTE sections can be 8 bytes for 64-bit ELF files. We
should put all adjacent SHT_NOTE sections with the same section alignment
into a single PT_NOTE segment even when the section alignment != 4 bytes.
Also check SHT_NOTE section type instead of section name.
PR ld/23658
* elf.c (get_program_header_size): Put all adjacent SHT_NOTE
sections with the same section alignment into a single PT_NOTE
segment. Check SHT_NOTE section type instead of section name.
(_bfd_elf_map_sections_to_segments): Likewise.
---
bfd/elf.c | 59 +++++++++++++++++++++++++++----------------------------
1 file changed, 29 insertions(+), 30 deletions(-)
diff --git a/bfd/elf.c b/bfd/elf.c
index 5320ae2237..8850efe20e 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -4371,23 +4371,22 @@ get_program_header_size (bfd *abfd, struct bfd_link_info *info)
for (s = abfd->sections; s != NULL; s = s->next)
{
if ((s->flags & SEC_LOAD) != 0
- && CONST_STRNEQ (s->name, ".note"))
+ && elf_section_type (s) == SHT_NOTE)
{
+ unsigned int alignment_power;
/* We need a PT_NOTE segment. */
++segs;
- /* Try to create just one PT_NOTE segment
- for all adjacent loadable .note* sections.
- gABI requires that within a PT_NOTE segment
- (and also inside of each SHT_NOTE section)
- each note is padded to a multiple of 4 size,
- so we check whether the sections are correctly
- aligned. */
- if (s->alignment_power == 2)
- while (s->next != NULL
- && s->next->alignment_power == 2
- && (s->next->flags & SEC_LOAD) != 0
- && CONST_STRNEQ (s->next->name, ".note"))
- s = s->next;
+ /* Try to create just one PT_NOTE segment for all adjacent
+ loadable SHT_NOTE sections. gABI requires that within a
+ PT_NOTE segment (and also inside of each SHT_NOTE section)
+ each note should have the same alignment. So we check
+ whether the sections are correctly aligned. */
+ alignment_power = s->alignment_power;
+ while (s->next != NULL
+ && s->next->alignment_power == alignment_power
+ && (s->next->flags & SEC_LOAD) != 0
+ && elf_section_type (s->next) == SHT_NOTE)
+ s = s->next;
}
}
@@ -4885,33 +4884,33 @@ _bfd_elf_map_sections_to_segments (bfd *abfd, struct bfd_link_info *info)
pm = &m->next;
}
- /* For each batch of consecutive loadable .note sections,
+ /* For each batch of consecutive loadable SHT_NOTE sections,
add a PT_NOTE segment. We don't use bfd_get_section_by_name,
because if we link together nonloadable .note sections and
loadable .note sections, we will generate two .note sections
- in the output file. FIXME: Using names for section types is
- bogus anyhow. */
+ in the output file. */
for (s = abfd->sections; s != NULL; s = s->next)
{
if ((s->flags & SEC_LOAD) != 0
- && CONST_STRNEQ (s->name, ".note"))
+ && elf_section_type (s) == SHT_NOTE)
{
asection *s2;
+ unsigned int alignment_power = s->alignment_power;
count = 1;
amt = sizeof (struct elf_segment_map);
- if (s->alignment_power == 2)
- for (s2 = s; s2->next != NULL; s2 = s2->next)
- {
- if (s2->next->alignment_power == 2
- && (s2->next->flags & SEC_LOAD) != 0
- && CONST_STRNEQ (s2->next->name, ".note")
- && align_power (s2->lma + s2->size, 2)
- == s2->next->lma)
- count++;
- else
- break;
- }
+ for (s2 = s; s2->next != NULL; s2 = s2->next)
+ {
+ if (s2->next->alignment_power == alignment_power
+ && (s2->next->flags & SEC_LOAD) != 0
+ && elf_section_type (s2->next) == SHT_NOTE
+ && align_power (s2->lma + s2->size,
+ alignment_power)
+ == s2->next->lma)
+ count++;
+ else
+ break;
+ }
amt += (count - 1) * sizeof (asection *);
m = (struct elf_segment_map *) bfd_zalloc (abfd, amt);
if (m == NULL)
--
2.17.1