PR30592 objcopy: allow --set-section-flags to add or remove SHF_X86_64_LARGE
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Commit Message
For example, objcopy --set-section-flags .data=alloc,large will add
SHF_X86_64_LARGE to the .data section. Omitting "large" will drop the
SHF_X86_64_LARGE flag.
The bfd_section flag is named generically, SEC_ELF_LARGE, in case other
processors want to follow SHF_X86_64_LARGE.
bfd/
* bfd-in2.h: Define SEC_ELF_LARGE.
* elf.c (_bfd_elf_make_section_from_shdr): Check SHF_X86_64_LARGE.
(elf_fake_sections): Check SEC_ELF_LARGE.
(_bfd_elf_init_private_section_data): Drop SHF_X86_64_LARGE for
x86-64.
binutils/
* doc/binutils.texi: Mention "large".
* objcopy.c (parse_flags): Parse "large".
* testsuite/binutils-all/x86-64/large-sections.d: New.
* testsuite/binutils-all/x86-64/large-sections.s: New.
* testsuite/binutils-all/x86-64/large-sections-2.d: New.
* testsuite/binutils-all/x86-64/large-sections-2.s: New.
include/
* elf/common.h: Define SHF_X86_64_LARGE to be used by elf.c.
---
bfd/bfd-in2.h | 3 +++
bfd/elf.c | 9 +++++++++
binutils/doc/binutils.texi | 15 ++++++++-------
binutils/objcopy.c | 3 ++-
.../binutils-all/x86-64/large-sections-2.d | 15 +++++++++++++++
.../binutils-all/x86-64/large-sections-2.s | 4 ++++
.../binutils-all/x86-64/large-sections.d | 14 ++++++++++++++
.../binutils-all/x86-64/large-sections.s | 8 ++++++++
include/elf/common.h | 2 ++
9 files changed, 65 insertions(+), 8 deletions(-)
create mode 100644 binutils/testsuite/binutils-all/x86-64/large-sections-2.d
create mode 100644 binutils/testsuite/binutils-all/x86-64/large-sections-2.s
create mode 100644 binutils/testsuite/binutils-all/x86-64/large-sections.d
create mode 100644 binutils/testsuite/binutils-all/x86-64/large-sections.s
Comments
On Jun 27 2023, Fangrui Song via Binutils wrote:
> diff --git a/bfd/elf.c b/bfd/elf.c
> index 8f6d7d1adba..d6e21b11419 100644
> --- a/bfd/elf.c
> +++ b/bfd/elf.c
> @@ -1034,6 +1034,10 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
> if ((hdr->sh_flags & SHF_EXCLUDE) != 0)
> flags |= SEC_EXCLUDE;
>
> + if (get_elf_backend_data (abfd)->elf_machine_code == EM_X86_64)
> + if ((hdr->sh_flags & SHF_X86_64_LARGE) != 0)
> + flags |= SEC_ELF_LARGE;
> +
> switch (elf_elfheader (abfd)->e_ident[EI_OSABI])
> {
> /* FIXME: We should not recognize SHF_GNU_MBIND for ELFOSABI_NONE,
> @@ -3351,6 +3355,8 @@ elf_fake_sections (bfd *abfd, asection *asect, void *fsarg)
> }
> if ((asect->flags & (SEC_GROUP | SEC_EXCLUDE)) == SEC_EXCLUDE)
> this_hdr->sh_flags |= SHF_EXCLUDE;
> + if (asect->flags & SEC_ELF_LARGE)
> + this_hdr->sh_flags |= SHF_X86_64_LARGE;
Doesn't that need to be conditional on EM_X86_64 as well? I don't see
anything that blocks SEC_ELF_LARGE from being set on incompatible
objects.
> diff --git a/binutils/doc/binutils.texi b/binutils/doc/binutils.texi
> index 8c14d1121d9..4dd7b83aaa6 100644
> --- a/binutils/doc/binutils.texi
> +++ b/binutils/doc/binutils.texi
> @@ -1740,13 +1740,14 @@ Set the flags for any sections matching @var{sectionpattern}. The
> @var{flags} argument is a comma separated string of flag names. The
> recognized names are @samp{alloc}, @samp{contents}, @samp{load},
> @samp{noload}, @samp{readonly}, @samp{code}, @samp{data}, @samp{rom},
> -@samp{exclude}, @samp{share}, and @samp{debug}. You can set the
> -@samp{contents} flag for a section which does not have contents, but it
> -is not meaningful to clear the @samp{contents} flag of a section which
> -does have contents--just remove the section instead. Not all flags are
> -meaningful for all object file formats. In particular the
> -@samp{share} flag is only meaningful for COFF format files and not for
> -ELF format files.
> +@samp{exclude}, @samp{share}, @samp{debug}, and @samp{large}.
> +You can set the @samp{contents} flag for a section which does not have
> +contents, but it is not meaningful to clear the @samp{contents} flag of a
> +section which does have contents--just remove the section instead. Not all
> +flags are meaningful for all object file formats. In particular the
> +@samp{share} flag is only meaningful for COFF format files and not for ELF
> +format files. @samp{large} is an ELF x86-64 specific flag that corresponds to
> +SHF_X86_64_LARGE.
The last sentence needs to be rearranged so that it doesn't start with a
lower case word.
On Wed, Jun 28, 2023 at 12:29 AM Andreas Schwab <schwab@suse.de> wrote:
>
> On Jun 27 2023, Fangrui Song via Binutils wrote:
>
> > diff --git a/bfd/elf.c b/bfd/elf.c
> > index 8f6d7d1adba..d6e21b11419 100644
> > --- a/bfd/elf.c
> > +++ b/bfd/elf.c
> > @@ -1034,6 +1034,10 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
> > if ((hdr->sh_flags & SHF_EXCLUDE) != 0)
> > flags |= SEC_EXCLUDE;
> >
> > + if (get_elf_backend_data (abfd)->elf_machine_code == EM_X86_64)
> > + if ((hdr->sh_flags & SHF_X86_64_LARGE) != 0)
> > + flags |= SEC_ELF_LARGE;
> > +
> > switch (elf_elfheader (abfd)->e_ident[EI_OSABI])
> > {
> > /* FIXME: We should not recognize SHF_GNU_MBIND for ELFOSABI_NONE,
> > @@ -3351,6 +3355,8 @@ elf_fake_sections (bfd *abfd, asection *asect, void *fsarg)
> > }
> > if ((asect->flags & (SEC_GROUP | SEC_EXCLUDE)) == SEC_EXCLUDE)
> > this_hdr->sh_flags |= SHF_EXCLUDE;
> > + if (asect->flags & SEC_ELF_LARGE)
> > + this_hdr->sh_flags |= SHF_X86_64_LARGE;
>
> Doesn't that need to be conditional on EM_X86_64 as well? I don't see
> anything that blocks SEC_ELF_LARGE from being set on incompatible
> objects.
>
> > diff --git a/binutils/doc/binutils.texi b/binutils/doc/binutils.texi
> > index 8c14d1121d9..4dd7b83aaa6 100644
> > --- a/binutils/doc/binutils.texi
> > +++ b/binutils/doc/binutils.texi
> > @@ -1740,13 +1740,14 @@ Set the flags for any sections matching @var{sectionpattern}. The
> > @var{flags} argument is a comma separated string of flag names. The
> > recognized names are @samp{alloc}, @samp{contents}, @samp{load},
> > @samp{noload}, @samp{readonly}, @samp{code}, @samp{data}, @samp{rom},
> > -@samp{exclude}, @samp{share}, and @samp{debug}. You can set the
> > -@samp{contents} flag for a section which does not have contents, but it
> > -is not meaningful to clear the @samp{contents} flag of a section which
> > -does have contents--just remove the section instead. Not all flags are
> > -meaningful for all object file formats. In particular the
> > -@samp{share} flag is only meaningful for COFF format files and not for
> > -ELF format files.
> > +@samp{exclude}, @samp{share}, @samp{debug}, and @samp{large}.
> > +You can set the @samp{contents} flag for a section which does not have
> > +contents, but it is not meaningful to clear the @samp{contents} flag of a
> > +section which does have contents--just remove the section instead. Not all
> > +flags are meaningful for all object file formats. In particular the
> > +@samp{share} flag is only meaningful for COFF format files and not for ELF
> > +format files. @samp{large} is an ELF x86-64 specific flag that corresponds to
> > +SHF_X86_64_LARGE.
>
> The last sentence needs to be rearranged so that it doesn't start with a
> lower case word.
>
> --
> Andreas Schwab, SUSE Labs, schwab@suse.de
> GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
> "And now for something completely different."
Thanks for the comments. Uploaded v2
https://sourceware.org/pipermail/binutils/2023-June/128078.html
@@ -633,6 +633,9 @@ typedef struct bfd_section
/* This section contains vliw code. This is for Toshiba MeP only. */
#define SEC_MEP_VLIW 0x20000000
+ /* This section has the SHF_X86_64_LARGE flag. This is ELF x86-64 only. */
+#define SEC_ELF_LARGE 0x20000000
+
/* All symbols, sizes and relocations in this section are octets
instead of bytes. Required for DWARF debug sections as DWARF
information is organized in octets, not bytes. */
@@ -1034,6 +1034,10 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
if ((hdr->sh_flags & SHF_EXCLUDE) != 0)
flags |= SEC_EXCLUDE;
+ if (get_elf_backend_data (abfd)->elf_machine_code == EM_X86_64)
+ if ((hdr->sh_flags & SHF_X86_64_LARGE) != 0)
+ flags |= SEC_ELF_LARGE;
+
switch (elf_elfheader (abfd)->e_ident[EI_OSABI])
{
/* FIXME: We should not recognize SHF_GNU_MBIND for ELFOSABI_NONE,
@@ -3351,6 +3355,8 @@ elf_fake_sections (bfd *abfd, asection *asect, void *fsarg)
}
if ((asect->flags & (SEC_GROUP | SEC_EXCLUDE)) == SEC_EXCLUDE)
this_hdr->sh_flags |= SHF_EXCLUDE;
+ if (asect->flags & SEC_ELF_LARGE)
+ this_hdr->sh_flags |= SHF_X86_64_LARGE;
/* If the section has relocs, set up a section header for the
SHT_REL[A] section. If two relocation sections are required for
@@ -7940,6 +7946,9 @@ _bfd_elf_init_private_section_data (bfd *ibfd,
elf_section_flags (osec) = (elf_section_flags (isec)
& (SHF_MASKOS | SHF_MASKPROC));
+ if (get_elf_backend_data (ibfd)->elf_machine_code == EM_X86_64)
+ elf_section_flags (osec) = (elf_section_flags (isec) & ~SHF_X86_64_LARGE);
+
/* Copy sh_info from input for mbind section. */
if ((elf_tdata (ibfd)->has_gnu_osabi & elf_gnu_osabi_mbind) != 0
&& elf_section_flags (isec) & SHF_GNU_MBIND)
@@ -1740,13 +1740,14 @@ Set the flags for any sections matching @var{sectionpattern}. The
@var{flags} argument is a comma separated string of flag names. The
recognized names are @samp{alloc}, @samp{contents}, @samp{load},
@samp{noload}, @samp{readonly}, @samp{code}, @samp{data}, @samp{rom},
-@samp{exclude}, @samp{share}, and @samp{debug}. You can set the
-@samp{contents} flag for a section which does not have contents, but it
-is not meaningful to clear the @samp{contents} flag of a section which
-does have contents--just remove the section instead. Not all flags are
-meaningful for all object file formats. In particular the
-@samp{share} flag is only meaningful for COFF format files and not for
-ELF format files.
+@samp{exclude}, @samp{share}, @samp{debug}, and @samp{large}.
+You can set the @samp{contents} flag for a section which does not have
+contents, but it is not meaningful to clear the @samp{contents} flag of a
+section which does have contents--just remove the section instead. Not all
+flags are meaningful for all object file formats. In particular the
+@samp{share} flag is only meaningful for COFF format files and not for ELF
+format files. @samp{large} is an ELF x86-64 specific flag that corresponds to
+SHF_X86_64_LARGE.
@item --set-section-alignment @var{sectionpattern}=@var{align}
Set the alignment for any sections matching @var{sectionpattern}.
@@ -797,6 +797,7 @@ parse_flags (const char *s)
PARSE_FLAG ("contents", SEC_HAS_CONTENTS);
PARSE_FLAG ("merge", SEC_MERGE);
PARSE_FLAG ("strings", SEC_STRINGS);
+ PARSE_FLAG ("large", SEC_ELF_LARGE);
#undef PARSE_FLAG
else
{
@@ -807,7 +808,7 @@ parse_flags (const char *s)
copy[len] = '\0';
non_fatal (_("unrecognized section flag `%s'"), copy);
fatal (_("supported flags: %s"),
- "alloc, load, noload, readonly, debug, code, data, rom, exclude, share, contents, merge, strings");
+ "alloc, load, noload, readonly, debug, code, data, rom, exclude, share, contents, merge, strings, large");
}
s = snext;
new file mode 100644
@@ -0,0 +1,15 @@
+#source: large-sections.s
+#PROG: objcopy
+#as: --64
+#objcopy: --set-section-flags .ldata=alloc
+#readelf: -S -W
+
+#...
+ \[[ 0-9]+\] \.text.*[ \t]+PROGBITS[ \t0-9a-f]+AX[ \t]+.*
+#...
+ \[[ 0-9]+\] \.data.*[ \t]+PROGBITS[ \t0-9a-f]+WA[ \t]+.*
+#...
+ \[[ 0-9]+\] \.ltext.*[ \t]+PROGBITS[ \t0-9a-f]+AXl[ \t]+.*
+#...
+ \[[ 0-9]+\] \.ldata.*[ \t]+PROGBITS[ \t0-9a-f]+WA[ \t]+.*
+#pass
new file mode 100644
@@ -0,0 +1,4 @@
+ .section .text, "axl"
+ nop
+ .section .data, "awl"
+ .byte 1
new file mode 100644
@@ -0,0 +1,14 @@
+#PROG: objcopy
+#as: --64
+#objcopy: --set-section-flags .text=alloc,readonly,code,large --set-section-flags .data=alloc,large
+#readelf: -S -W
+
+#...
+ \[[ 0-9]+\] \.text.*[ \t]+PROGBITS[ \t0-9a-f]+AXl[ \t]+.*
+#...
+ \[[ 0-9]+\] \.data.*[ \t]+PROGBITS[ \t0-9a-f]+WAl[ \t]+.*
+#...
+ \[[ 0-9]+\] \.ltext.*[ \t]+PROGBITS[ \t0-9a-f]+AXl[ \t]+.*
+#...
+ \[[ 0-9]+\] \.ldata.*[ \t]+PROGBITS[ \t0-9a-f]+WAl[ \t]+.*
+#pass
new file mode 100644
@@ -0,0 +1,8 @@
+ .section .text, "ax"
+ nop
+ .section .data, "aw"
+ .byte 1
+ .section .ltext, "axl"
+ nop
+ .section .ldata, "awl"
+ .byte 1
@@ -588,6 +588,8 @@
#define SHF_GNU_MBIND 0x01000000 /* Mbind section. */
+#define SHF_X86_64_LARGE 0x10000000
+
/* Compression types. */
#define ELFCOMPRESS_ZLIB 1 /* Compressed with zlib. */
#define ELFCOMPRESS_ZSTD 2 /* Compressed with zstd */