* [binutils-gdb] ELF: Strip section header in ELF objects
@ 2023-06-29 17:36 H.J. Lu
0 siblings, 0 replies; only message in thread
From: H.J. Lu @ 2023-06-29 17:36 UTC (permalink / raw)
To: bfd-cvs
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=96cc7918c18cdb7bd0331d836fa7f05341732580
commit 96cc7918c18cdb7bd0331d836fa7f05341732580
Author: Kaylee Blake <klkblake@gmail.com>
Date: Wed Mar 4 19:18:07 2020 +1030
ELF: Strip section header in ELF objects
Section header isn't mandatory on ELF executable nor shared library.
This patch adds a new linker option, -z nosectionheader, to omit ELF
section header, a new objcopy and strip option, --strip-section-headers,
to remove ELF section headers.
bfd/
2023-06-06 H.J. Lu <hongjiu.lu@intel.com>
Kaylee Blake <klkblake@gmail.com>
PR ld/25617
* bfd.c (BFD_NO_SECTION_HEADER): New.
(BFD_FLAGS_SAVED): Add BFD_NO_SECTION_HEADER.
(BFD_FLAGS_FOR_BFD_USE_MASK): Likewise.
* elfcode.h (elf_swap_ehdr_out): Omit section header with
BFD_NO_SECTION_HEADER.
(elf_write_shdrs_and_ehdr): Likewise.
* elfxx-target.h (TARGET_BIG_SYM): Add BFD_NO_SECTION_HEADER
to object_flags.
(TARGET_LITTLE_SYM): Likewise.
* bfd-in2.h: Regenerated.
binutils/
2023-06-06 H.J. Lu <hongjiu.lu@intel.com>
PR ld/25617
* NEWS: Mention --strip-section-headers for objcopy and strip.
* objcopy.c (strip_section_headers): New.
(command_line_switch): Add OPTION_STRIP_SECTION_HEADERS.
(strip_options): Add --strip-section-headers.
(copy_options): Likewise.
(copy_usage): Add --strip-section-headers.
(strip_usage): Likewise.
(copy_object): Handle --strip-section-headers for ELF files.
(strip_main): Handle OPTION_STRIP_SECTION_HEADERS.
(copy_main): Likewise.
* doc/binutils.texi: Document --strip-section-headers for objcopy
and strip.
ld/
2023-06-06 H.J. Lu <hongjiu.lu@intel.com>
Kaylee Blake <klkblake@gmail.com>
PR ld/25617
* NEWS: Mention -z nosectionheader.
* emultempl/elf.em: Support -z sectionheader and
-z nosectionheader.
* ld.h (ld_config_type): Add no_section_header.
* ld.texi: Document -z sectionheader and -z nosectionheader.
* ldlang.c (ldlang_open_output): Handle
config.no_section_header.
* lexsup.c (parse_args): Enable --strip-all with
-z nosectionheader. Disallow -r with -z nosectionheader.
(elf_static_list_options): Add -z sectionheader and
-z nosectionheader.
Diff:
---
bfd/bfd-in2.h | 6 +++++-
bfd/bfd.c | 6 +++++-
bfd/elfcode.h | 36 ++++++++++++++++++++++++++----------
bfd/elfxx-target.h | 4 ++--
binutils/NEWS | 3 +++
binutils/doc/binutils.texi | 10 ++++++++++
binutils/objcopy.c | 33 +++++++++++++++++++++++++++++++--
ld/NEWS | 3 +++
ld/emultempl/elf.em | 4 ++++
ld/ld.h | 3 +++
ld/ld.texi | 5 +++++
ld/ldlang.c | 4 ++++
ld/lexsup.c | 13 +++++++++++++
13 files changed, 114 insertions(+), 16 deletions(-)
diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index c4fa0c1f9bf..b34c8ef9fc9 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -2049,11 +2049,15 @@ struct bfd
/* Compress sections in this BFD with SHF_COMPRESSED zstd. */
#define BFD_COMPRESS_ZSTD 0x400000
+ /* Don't generate ELF section header. */
+#define BFD_NO_SECTION_HEADER 0x800000
+
/* Flags bits which are for BFD use only. */
#define BFD_FLAGS_FOR_BFD_USE_MASK \
(BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_LINKER_CREATED \
| BFD_PLUGIN | BFD_TRADITIONAL_FORMAT | BFD_DETERMINISTIC_OUTPUT \
- | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON | BFD_USE_ELF_STT_COMMON)
+ | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON | BFD_USE_ELF_STT_COMMON \
+ | BFD_NO_SECTION_HEADER)
/* The format which belongs to the BFD. (object, core, etc.) */
ENUM_BITFIELD (bfd_format) format : 3;
diff --git a/bfd/bfd.c b/bfd/bfd.c
index 804acabf621..e43a388ac72 100644
--- a/bfd/bfd.c
+++ b/bfd/bfd.c
@@ -192,11 +192,15 @@ CODE_FRAGMENT
. {* Compress sections in this BFD with SHF_COMPRESSED zstd. *}
.#define BFD_COMPRESS_ZSTD 0x400000
.
+. {* Don't generate ELF section header. *}
+.#define BFD_NO_SECTION_HEADER 0x800000
+.
. {* Flags bits which are for BFD use only. *}
.#define BFD_FLAGS_FOR_BFD_USE_MASK \
. (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_LINKER_CREATED \
. | BFD_PLUGIN | BFD_TRADITIONAL_FORMAT | BFD_DETERMINISTIC_OUTPUT \
-. | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON | BFD_USE_ELF_STT_COMMON)
+. | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON | BFD_USE_ELF_STT_COMMON \
+. | BFD_NO_SECTION_HEADER)
.
. {* The format which belongs to the BFD. (object, core, etc.) *}
. ENUM_BITFIELD (bfd_format) format : 3;
diff --git a/bfd/elfcode.h b/bfd/elfcode.h
index e4e29f0dc57..495e498838d 100644
--- a/bfd/elfcode.h
+++ b/bfd/elfcode.h
@@ -266,6 +266,7 @@ elf_swap_ehdr_out (bfd *abfd,
{
unsigned int tmp;
int signed_vma = get_elf_backend_data (abfd)->sign_extend_vma;
+ bool no_section_header = (abfd->flags & BFD_NO_SECTION_HEADER) != 0;
memcpy (dst->e_ident, src->e_ident, EI_NIDENT);
/* note that all elements of dst are *arrays of unsigned char* already... */
H_PUT_16 (abfd, src->e_type, dst->e_type);
@@ -276,7 +277,10 @@ elf_swap_ehdr_out (bfd *abfd,
else
H_PUT_WORD (abfd, src->e_entry, dst->e_entry);
H_PUT_WORD (abfd, src->e_phoff, dst->e_phoff);
- H_PUT_WORD (abfd, src->e_shoff, dst->e_shoff);
+ if (no_section_header)
+ H_PUT_WORD (abfd, 0, dst->e_shoff);
+ else
+ H_PUT_WORD (abfd, src->e_shoff, dst->e_shoff);
H_PUT_32 (abfd, src->e_flags, dst->e_flags);
H_PUT_16 (abfd, src->e_ehsize, dst->e_ehsize);
H_PUT_16 (abfd, src->e_phentsize, dst->e_phentsize);
@@ -284,15 +288,24 @@ elf_swap_ehdr_out (bfd *abfd,
if (tmp > PN_XNUM)
tmp = PN_XNUM;
H_PUT_16 (abfd, tmp, dst->e_phnum);
- H_PUT_16 (abfd, src->e_shentsize, dst->e_shentsize);
- tmp = src->e_shnum;
- if (tmp >= (SHN_LORESERVE & 0xffff))
- tmp = SHN_UNDEF;
- H_PUT_16 (abfd, tmp, dst->e_shnum);
- tmp = src->e_shstrndx;
- if (tmp >= (SHN_LORESERVE & 0xffff))
- tmp = SHN_XINDEX & 0xffff;
- H_PUT_16 (abfd, tmp, dst->e_shstrndx);
+ if (no_section_header)
+ {
+ H_PUT_16 (abfd, 0, dst->e_shentsize);
+ H_PUT_16 (abfd, 0, dst->e_shnum);
+ H_PUT_16 (abfd, 0, dst->e_shstrndx);
+ }
+ else
+ {
+ H_PUT_16 (abfd, src->e_shentsize, dst->e_shentsize);
+ tmp = src->e_shnum;
+ if (tmp >= (SHN_LORESERVE & 0xffff))
+ tmp = SHN_UNDEF;
+ H_PUT_16 (abfd, tmp, dst->e_shnum);
+ tmp = src->e_shstrndx;
+ if (tmp >= (SHN_LORESERVE & 0xffff))
+ tmp = SHN_XINDEX & 0xffff;
+ H_PUT_16 (abfd, tmp, dst->e_shstrndx);
+ }
}
/* Translate an ELF section header table entry in external format into an
@@ -1077,6 +1090,9 @@ elf_write_shdrs_and_ehdr (bfd *abfd)
|| bfd_bwrite (&x_ehdr, amt, abfd) != amt)
return false;
+ if ((abfd->flags & BFD_NO_SECTION_HEADER) != 0)
+ return true;
+
/* Some fields in the first section header handle overflow of ehdr
fields. */
if (i_ehdrp->e_phnum >= PN_XNUM)
diff --git a/bfd/elfxx-target.h b/bfd/elfxx-target.h
index 8eabad4bd3f..f8553006385 100644
--- a/bfd/elfxx-target.h
+++ b/bfd/elfxx-target.h
@@ -994,7 +994,7 @@ const bfd_target TARGET_BIG_SYM =
(HAS_RELOC | EXEC_P | HAS_LINENO | HAS_DEBUG | HAS_SYMS | HAS_LOCALS
| DYNAMIC | WP_TEXT | D_PAGED | BFD_COMPRESS | BFD_DECOMPRESS
| BFD_COMPRESS_GABI | BFD_COMPRESS_ZSTD | BFD_CONVERT_ELF_COMMON
- | BFD_USE_ELF_STT_COMMON),
+ | BFD_USE_ELF_STT_COMMON | BFD_NO_SECTION_HEADER),
/* section_flags: mask of all section flags */
(SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD | SEC_RELOC | SEC_READONLY
@@ -1099,7 +1099,7 @@ const bfd_target TARGET_LITTLE_SYM =
(HAS_RELOC | EXEC_P | HAS_LINENO | HAS_DEBUG | HAS_SYMS | HAS_LOCALS
| DYNAMIC | WP_TEXT | D_PAGED | BFD_COMPRESS | BFD_DECOMPRESS
| BFD_COMPRESS_GABI | BFD_COMPRESS_ZSTD | BFD_CONVERT_ELF_COMMON
- | BFD_USE_ELF_STT_COMMON),
+ | BFD_USE_ELF_STT_COMMON | BFD_NO_SECTION_HEADER),
/* section_flags: mask of all section flags */
(SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD | SEC_RELOC | SEC_READONLY
diff --git a/binutils/NEWS b/binutils/NEWS
index 00ef7c43610..3aea8755339 100644
--- a/binutils/NEWS
+++ b/binutils/NEWS
@@ -14,6 +14,9 @@
sframe_get_funcdesc_with_addr API, change in the behavior of
sframe_fre_get_ra_offset and sframe_fre_get_fp_offset APIs.
+* Add command-line option, --strip-section-headers, to objcopy and strip to
+ remove ELF section header from ELF file.
+
Changes in 2.40:
* Objdump has a new command line option --show-all-symbols which will make it
diff --git a/binutils/doc/binutils.texi b/binutils/doc/binutils.texi
index 8c14d1121d9..8314cb57562 100644
--- a/binutils/doc/binutils.texi
+++ b/binutils/doc/binutils.texi
@@ -1278,6 +1278,7 @@ objcopy [@option{-F} @var{bfdname}|@option{--target=}@var{bfdname}]
[@option{-R} @var{sectionpattern}|@option{--remove-section=}@var{sectionpattern}]
[@option{--keep-section=}@var{sectionpattern}]
[@option{--remove-relocations=}@var{sectionpattern}]
+ [@option{--strip-section-headers}]
[@option{-p}|@option{--preserve-dates}]
[@option{-D}|@option{--enable-deterministic-archives}]
[@option{-U}|@option{--disable-deterministic-archives}]
@@ -1494,6 +1495,10 @@ will remove all relocations for sections matching the pattern
'.text.*', but will not remove relocations for the section
'.text.foo'.
+@item --strip-section-headers
+Strip section header This option is specific to ELF files.
+Implies @option{--strip-all} and @option{--merge-notes}.
+
@item -S
@itemx --strip-all
Do not copy relocation and symbol information from the source file.
@@ -3484,6 +3489,7 @@ strip [@option{-F} @var{bfdname} |@option{--target=}@var{bfdname}]
[@option{-R} @var{sectionname} |@option{--remove-section=}@var{sectionname}]
[@option{--keep-section=}@var{sectionpattern}]
[@option{--remove-relocations=}@var{sectionpattern}]
+ [@option{--strip-section-headers}]
[@option{-o} @var{file}] [@option{-p}|@option{--preserve-dates}]
[@option{-D}|@option{--enable-deterministic-archives}]
[@option{-U}|@option{--disable-deterministic-archives}]
@@ -3586,6 +3592,10 @@ will remove all relocations for sections matching the pattern
'.text.*', but will not remove relocations for the section
'.text.foo'.
+@item --strip-section-headers
+Strip section headers. This option is specific to ELF files. Implies
+@option{--strip-all} and @option{--merge-notes}.
+
@item -s
@itemx --strip-all
Remove all symbols.
diff --git a/binutils/objcopy.c b/binutils/objcopy.c
index 414007780a8..206d80bd0f1 100644
--- a/binutils/objcopy.c
+++ b/binutils/objcopy.c
@@ -97,6 +97,7 @@ static int deterministic = -1; /* Enable deterministic archives. */
static int status = 0; /* Exit status. */
static bool merge_notes = false; /* Merge note sections. */
+static bool strip_section_headers = false;/* Strip section headers. */
typedef struct merged_note_section
{
@@ -365,6 +366,7 @@ enum command_line_switch
OPTION_SREC_LEN,
OPTION_STACK,
OPTION_STRIP_DWO,
+ OPTION_STRIP_SECTION_HEADERS,
OPTION_STRIP_SYMBOLS,
OPTION_STRIP_UNNEEDED,
OPTION_STRIP_UNNEEDED_SYMBOL,
@@ -403,6 +405,7 @@ static struct option strip_options[] =
{"preserve-dates", no_argument, 0, 'p'},
{"remove-section", required_argument, 0, 'R'},
{"remove-relocations", required_argument, 0, OPTION_REMOVE_RELOCS},
+ {"strip-section-headers", no_argument, 0, OPTION_STRIP_SECTION_HEADERS},
{"strip-all", no_argument, 0, 's'},
{"strip-debug", no_argument, 0, 'S'},
{"strip-dwo", no_argument, 0, OPTION_STRIP_DWO},
@@ -492,6 +495,7 @@ static struct option copy_options[] =
{"remove-leading-char", no_argument, 0, OPTION_REMOVE_LEADING_CHAR},
{"remove-section", required_argument, 0, 'R'},
{"remove-relocations", required_argument, 0, OPTION_REMOVE_RELOCS},
+ {"strip-section-headers", no_argument, 0, OPTION_STRIP_SECTION_HEADERS},
{"rename-section", required_argument, 0, OPTION_RENAME_SECTION},
{"reverse-bytes", required_argument, 0, OPTION_REVERSE_BYTES},
{"section-alignment", required_argument, 0, OPTION_PE_SECTION_ALIGNMENT},
@@ -592,6 +596,7 @@ copy_usage (FILE *stream, int exit_status)
--add-gnu-debuglink=<file> Add section .gnu_debuglink linking to <file>\n\
-R --remove-section <name> Remove section <name> from the output\n\
--remove-relocations <name> Remove relocations from section <name>\n\
+ --strip-section-headers Strip section header from the output\n\
-S --strip-all Remove all symbol and relocation information\n\
-g --strip-debug Remove all debugging symbols & sections\n\
--strip-dwo Remove all DWO sections\n\
@@ -730,6 +735,7 @@ strip_usage (FILE *stream, int exit_status)
fprintf (stream, _("\
-R --remove-section=<name> Also remove section <name> from the output\n\
--remove-relocations <name> Remove relocations from section <name>\n\
+ --strip-section-headers Strip section headers from the output\n\
-s --strip-all Remove all symbol and relocation information\n\
-g -S -d --strip-debug Remove all debugging symbols & sections\n\
--strip-dwo Remove all DWO sections\n\
@@ -2695,7 +2701,16 @@ copy_object (bfd *ibfd, bfd *obfd, const bfd_arch_info_type *input_arch)
necessary. */
VerilogDataEndianness = ibfd->xvec->byteorder;
- if (bfd_get_flavour (ibfd) != bfd_target_elf_flavour)
+ if (bfd_get_flavour (ibfd) == bfd_target_elf_flavour)
+ {
+ if (strip_section_headers)
+ {
+ ibfd->flags |= BFD_NO_SECTION_HEADER;
+ strip_symbols = STRIP_ALL;
+ merge_notes = true;
+ }
+ }
+ else
{
if ((do_debug_sections & compress) != 0
&& do_debug_sections != compress)
@@ -2712,6 +2727,13 @@ copy_object (bfd *ibfd, bfd *obfd, const bfd_arch_info_type *input_arch)
bfd_get_archive_filename (ibfd));
return false;
}
+
+ if (strip_section_headers)
+ {
+ non_fatal (_("--strip_section_headers is unsupported on `%s'"),
+ bfd_get_archive_filename (ibfd));
+ return false;
+ }
}
if (verbose)
@@ -3456,7 +3478,7 @@ copy_object (bfd *ibfd, bfd *obfd, const bfd_arch_info_type *input_arch)
free (merged);
}
}
- else if (merge_notes && ! is_strip)
+ else if (merge_notes && ! is_strip && ! strip_section_headers)
non_fatal (_("%s: Could not find any mergeable note sections"),
bfd_get_filename (ibfd));
@@ -4759,6 +4781,9 @@ strip_main (int argc, char *argv[])
case OPTION_REMOVE_RELOCS:
handle_remove_relocations_option (optarg);
break;
+ case OPTION_STRIP_SECTION_HEADERS:
+ strip_section_headers = true;
+ break;
case 's':
strip_symbols = STRIP_ALL;
break;
@@ -5228,6 +5253,10 @@ copy_main (int argc, char *argv[])
handle_remove_relocations_option (optarg);
break;
+ case OPTION_STRIP_SECTION_HEADERS:
+ strip_section_headers = true;
+ break;
+
case 'S':
strip_symbols = STRIP_ALL;
break;
diff --git a/ld/NEWS b/ld/NEWS
index 4dee2301158..dbeea1267a1 100644
--- a/ld/NEWS
+++ b/ld/NEWS
@@ -15,6 +15,9 @@
* The linker script syntax has a new command for output sections: ASCIZ "string"
This will insert a zero-terminated string at the current location.
+* Add command-line option, -z nosectionheader, to omit ELF section
+ header.
+
Changes in 2.40:
* The linker has a new command line option to suppress the generation of any
diff --git a/ld/emultempl/elf.em b/ld/emultempl/elf.em
index e367299146f..3f67f8b09d9 100644
--- a/ld/emultempl/elf.em
+++ b/ld/emultempl/elf.em
@@ -807,6 +807,10 @@ fragment <<EOF
"must be default, internal, hidden, or protected"),
optarg);
}
+ else if (strcmp (optarg, "sectionheader") == 0)
+ config.no_section_header = false;
+ else if (strcmp (optarg, "nosectionheader") == 0)
+ config.no_section_header = true;
EOF
if test x"$GENERATE_SHLIB_SCRIPT" = xyes; then
diff --git a/ld/ld.h b/ld/ld.h
index 1882a282020..a0f8a15c7a9 100644
--- a/ld/ld.h
+++ b/ld/ld.h
@@ -280,6 +280,9 @@ typedef struct
/* If set, code and non-code sections should never be in one segment. */
bool separate_code;
+ /* If set, generation of ELF section header should be suppressed. */
+ bool no_section_header;
+
/* The rpath separation character. Usually ':'. */
char rpath_separator;
diff --git a/ld/ld.texi b/ld/ld.texi
index a007ae7fade..aa8b1aa86eb 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -1544,6 +1544,11 @@ Don't create an ELF @code{PT_GNU_RELRO} segment if @samp{norelro}.
Report dynamic relative relocations generated by linker. Supported for
Linux/i386 and Linux/x86_64.
+@item sectionheader
+@itemx nosectionheader
+Generate section header. Don't generate section header if
+@samp{nosectionheader} is used. @option{sectionheader} is the default.
+
@item separate-code
@itemx noseparate-code
Create separate code @code{PT_LOAD} segment header in the object. This
diff --git a/ld/ldlang.c b/ld/ldlang.c
index e359a89fcc0..f4a8b72869e 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -3434,6 +3434,10 @@ ldlang_open_output (lang_statement_union_type *statement)
link_info.output_bfd->flags |= BFD_TRADITIONAL_FORMAT;
else
link_info.output_bfd->flags &= ~BFD_TRADITIONAL_FORMAT;
+ if (config.no_section_header)
+ link_info.output_bfd->flags |= BFD_NO_SECTION_HEADER;
+ else
+ link_info.output_bfd->flags &= ~BFD_NO_SECTION_HEADER;
break;
case lang_target_statement_enum:
diff --git a/ld/lexsup.c b/ld/lexsup.c
index 4e20e938a49..fe8722313fe 100644
--- a/ld/lexsup.c
+++ b/ld/lexsup.c
@@ -1998,6 +1998,15 @@ parse_args (unsigned argc, char **argv)
break;
}
+ /* -z nosectionheader implies --strip-all. */
+ if (config.no_section_header)
+ {
+ if (bfd_link_relocatable (&link_info))
+ einfo (_("%F%P: -r and -z nosectionheader may not be used together\n"));
+
+ link_info.strip = strip_all;
+ }
+
if (!bfd_link_dll (&link_info))
{
if (command_line.filter_shlib)
@@ -2272,6 +2281,10 @@ elf_static_list_options (FILE *file)
fprintf (file, _("\
-z start-stop-visibility=V Set visibility of built-in __start/__stop symbols\n\
to DEFAULT, PROTECTED, HIDDEN or INTERNAL\n"));
+ fprintf (file, _("\
+ -z sectionheader Generate section header (default)\n"));
+ fprintf (file, _("\
+ -z nosectionheader Do not generate section header\n"));
}
static void
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