[PATCH v3] PR30592 objcopy: allow --set-section-flags to add or remove SHF_X86_64_LARGE

Fangrui Song maskray@google.com
Fri Jul 7 05:43:06 GMT 2023


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.  SEC_ELF_LARGE has the same value
as SEC_TIC54X_CLINK and SEC_MEP_VLIW.

bfd/
    * section.c: Define SEC_ELF_LARGE.
    * bfd-in2.h: Regenerate.
    * 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 so that objcopy --set-section-flags without 'large'
    clears the section flag.

binutils/
    * NEWS: Mention the new feature for objcopy.
    * 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.

--
Changes from v1:

* Add an entry to binutils/NEWS
* Adjust doc/binutils.texi wording
* Guard a SEC_ELF_LARGE branch with EM_X86_64 check

Changes from v2:

* Address Jan's comments https://sourceware.org/pipermail/binutils/2023-July/128303.html
---
 bfd/bfd-in2.h                                     |  3 +++
 bfd/elf.c                                         | 12 +++++++++++-
 bfd/section.c                                     |  3 +++
 binutils/NEWS                                     |  3 +++
 binutils/doc/binutils.texi                        | 15 ++++++++-------
 binutils/objcopy.c                                |  4 +++-
 .../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 ++
 11 files changed, 74 insertions(+), 9 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

diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index b34c8ef9fc9..03767efb260 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -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.  */
diff --git a/bfd/elf.c b/bfd/elf.c
index d38e0afff2e..fe41798e413 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -1045,6 +1045,11 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
   if ((hdr->sh_flags & SHF_EXCLUDE) != 0)
     flags |= SEC_EXCLUDE;
 
+  bed = get_elf_backend_data (abfd);
+  if (bed->elf_machine_code == EM_X86_64 &&
+      (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,
@@ -1104,7 +1109,6 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
   if (!bfd_set_section_flags (newsect, flags))
     return false;
 
-  bed = get_elf_backend_data (abfd);
   if (bed->elf_backend_section_flags)
     if (!bed->elf_backend_section_flags (hdr))
       return false;
@@ -3912,6 +3916,8 @@ 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 (bed->elf_machine_code == EM_X86_64 && (asect->flags & SEC_ELF_LARGE) != 0)
+    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
@@ -8508,6 +8514,10 @@ _bfd_elf_init_private_section_data (bfd *ibfd,
   elf_section_flags (osec) = (elf_section_flags (isec)
 			      & (SHF_MASKOS | SHF_MASKPROC));
 
+  /* objcopy --set-section-flags without "large" drops SHF_X86_64_LARGE.  */
+  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)
diff --git a/bfd/section.c b/bfd/section.c
index 73770294e56..b7c771b4fb8 100644
--- a/bfd/section.c
+++ b/bfd/section.c
@@ -367,6 +367,9 @@ CODE_FRAGMENT
 .  {* 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.  *}
diff --git a/binutils/NEWS b/binutils/NEWS
index 563062c6904..cad877b943a 100644
--- a/binutils/NEWS
+++ b/binutils/NEWS
@@ -1,5 +1,8 @@
 -*- text -*-
 
+* objcopy's --set-section-flags now support "large" to set SHF_X86_64_LARGE
+  for ELF x86-64 objects.
+
 Changes in 2.41:
 
 * The MIPS port now supports the Sony Interactive Entertainment Allegrex
diff --git a/binutils/doc/binutils.texi b/binutils/doc/binutils.texi
index 8314cb57562..309bedf6110 100644
--- a/binutils/doc/binutils.texi
+++ b/binutils/doc/binutils.texi
@@ -1745,13 +1745,14 @@ 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.  The ELF x86-64 specific flag @samp{large} corresponds to
+SHF_X86_64_LARGE.
 
 @item --set-section-alignment @var{sectionpattern}=@var{align}
 Set the alignment for any sections matching @var{sectionpattern}.
diff --git a/binutils/objcopy.c b/binutils/objcopy.c
index 3569b890c7d..cb0d44ec0f4 100644
--- a/binutils/objcopy.c
+++ b/binutils/objcopy.c
@@ -803,6 +803,7 @@ 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
 	{
@@ -813,7 +814,8 @@ 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, (ELF x86-64 specific) large");
 	}
 
       s = snext;
diff --git a/binutils/testsuite/binutils-all/x86-64/large-sections-2.d b/binutils/testsuite/binutils-all/x86-64/large-sections-2.d
new file mode 100644
index 00000000000..29ace42cc9e
--- /dev/null
+++ b/binutils/testsuite/binutils-all/x86-64/large-sections-2.d
@@ -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
diff --git a/binutils/testsuite/binutils-all/x86-64/large-sections-2.s b/binutils/testsuite/binutils-all/x86-64/large-sections-2.s
new file mode 100644
index 00000000000..6f31aa93701
--- /dev/null
+++ b/binutils/testsuite/binutils-all/x86-64/large-sections-2.s
@@ -0,0 +1,4 @@
+	.section .text, "axl"
+	nop
+	.section .data, "awl"
+	.byte 1
diff --git a/binutils/testsuite/binutils-all/x86-64/large-sections.d b/binutils/testsuite/binutils-all/x86-64/large-sections.d
new file mode 100644
index 00000000000..5d945e46ba3
--- /dev/null
+++ b/binutils/testsuite/binutils-all/x86-64/large-sections.d
@@ -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
diff --git a/binutils/testsuite/binutils-all/x86-64/large-sections.s b/binutils/testsuite/binutils-all/x86-64/large-sections.s
new file mode 100644
index 00000000000..072e456a1ed
--- /dev/null
+++ b/binutils/testsuite/binutils-all/x86-64/large-sections.s
@@ -0,0 +1,8 @@
+	.section .text, "ax"
+	nop
+	.section .data, "aw"
+	.byte 1
+	.section .ltext, "axl"
+	nop
+	.section .ldata, "awl"
+	.byte 1
diff --git a/include/elf/common.h b/include/elf/common.h
index ffa6b60bd2b..1397d60402e 100644
--- a/include/elf/common.h
+++ b/include/elf/common.h
@@ -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  */
-- 
2.41.0.255.g8b1d071c50-goog



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