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.
This commit is contained in:
Kaylee Blake
H.J. Lu
parent
fa2b501cdc
commit
96cc7918c1
13 changed files with 114 additions and 16 deletions
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@ -2049,11 +2049,15 @@ struct bfd
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/* Compress sections in this BFD with SHF_COMPRESSED zstd. */
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#define BFD_COMPRESS_ZSTD 0x400000
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/* Don't generate ELF section header. */
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#define BFD_NO_SECTION_HEADER 0x800000
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/* Flags bits which are for BFD use only. */
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#define BFD_FLAGS_FOR_BFD_USE_MASK \
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(BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_LINKER_CREATED \
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| BFD_PLUGIN | BFD_TRADITIONAL_FORMAT | BFD_DETERMINISTIC_OUTPUT \
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| BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON | BFD_USE_ELF_STT_COMMON)
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| BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON | BFD_USE_ELF_STT_COMMON \
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| BFD_NO_SECTION_HEADER)
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/* The format which belongs to the BFD. (object, core, etc.) */
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ENUM_BITFIELD (bfd_format) format : 3;
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@ -192,11 +192,15 @@ CODE_FRAGMENT
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. {* Compress sections in this BFD with SHF_COMPRESSED zstd. *}
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.#define BFD_COMPRESS_ZSTD 0x400000
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.
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. {* Don't generate ELF section header. *}
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.#define BFD_NO_SECTION_HEADER 0x800000
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.
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. {* Flags bits which are for BFD use only. *}
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.#define BFD_FLAGS_FOR_BFD_USE_MASK \
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. (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_LINKER_CREATED \
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. | BFD_PLUGIN | BFD_TRADITIONAL_FORMAT | BFD_DETERMINISTIC_OUTPUT \
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. | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON | BFD_USE_ELF_STT_COMMON)
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. | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON | BFD_USE_ELF_STT_COMMON \
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. | BFD_NO_SECTION_HEADER)
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.
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. {* The format which belongs to the BFD. (object, core, etc.) *}
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. ENUM_BITFIELD (bfd_format) format : 3;
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@ -266,6 +266,7 @@ elf_swap_ehdr_out (bfd *abfd,
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{
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unsigned int tmp;
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int signed_vma = get_elf_backend_data (abfd)->sign_extend_vma;
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bool no_section_header = (abfd->flags & BFD_NO_SECTION_HEADER) != 0;
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memcpy (dst->e_ident, src->e_ident, EI_NIDENT);
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/* note that all elements of dst are *arrays of unsigned char* already... */
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H_PUT_16 (abfd, src->e_type, dst->e_type);
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@ -276,7 +277,10 @@ elf_swap_ehdr_out (bfd *abfd,
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else
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H_PUT_WORD (abfd, src->e_entry, dst->e_entry);
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H_PUT_WORD (abfd, src->e_phoff, dst->e_phoff);
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H_PUT_WORD (abfd, src->e_shoff, dst->e_shoff);
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if (no_section_header)
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H_PUT_WORD (abfd, 0, dst->e_shoff);
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else
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H_PUT_WORD (abfd, src->e_shoff, dst->e_shoff);
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H_PUT_32 (abfd, src->e_flags, dst->e_flags);
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H_PUT_16 (abfd, src->e_ehsize, dst->e_ehsize);
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H_PUT_16 (abfd, src->e_phentsize, dst->e_phentsize);
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@ -284,15 +288,24 @@ elf_swap_ehdr_out (bfd *abfd,
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if (tmp > PN_XNUM)
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tmp = PN_XNUM;
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H_PUT_16 (abfd, tmp, dst->e_phnum);
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H_PUT_16 (abfd, src->e_shentsize, dst->e_shentsize);
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tmp = src->e_shnum;
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if (tmp >= (SHN_LORESERVE & 0xffff))
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tmp = SHN_UNDEF;
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H_PUT_16 (abfd, tmp, dst->e_shnum);
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tmp = src->e_shstrndx;
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if (tmp >= (SHN_LORESERVE & 0xffff))
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tmp = SHN_XINDEX & 0xffff;
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H_PUT_16 (abfd, tmp, dst->e_shstrndx);
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if (no_section_header)
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{
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H_PUT_16 (abfd, 0, dst->e_shentsize);
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H_PUT_16 (abfd, 0, dst->e_shnum);
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H_PUT_16 (abfd, 0, dst->e_shstrndx);
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}
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else
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{
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H_PUT_16 (abfd, src->e_shentsize, dst->e_shentsize);
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tmp = src->e_shnum;
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if (tmp >= (SHN_LORESERVE & 0xffff))
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tmp = SHN_UNDEF;
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H_PUT_16 (abfd, tmp, dst->e_shnum);
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tmp = src->e_shstrndx;
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if (tmp >= (SHN_LORESERVE & 0xffff))
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tmp = SHN_XINDEX & 0xffff;
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H_PUT_16 (abfd, tmp, dst->e_shstrndx);
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}
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}
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/* Translate an ELF section header table entry in external format into an
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@ -1077,6 +1090,9 @@ elf_write_shdrs_and_ehdr (bfd *abfd)
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|| bfd_bwrite (&x_ehdr, amt, abfd) != amt)
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return false;
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if ((abfd->flags & BFD_NO_SECTION_HEADER) != 0)
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return true;
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/* Some fields in the first section header handle overflow of ehdr
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fields. */
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if (i_ehdrp->e_phnum >= PN_XNUM)
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@ -994,7 +994,7 @@ const bfd_target TARGET_BIG_SYM =
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(HAS_RELOC | EXEC_P | HAS_LINENO | HAS_DEBUG | HAS_SYMS | HAS_LOCALS
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| DYNAMIC | WP_TEXT | D_PAGED | BFD_COMPRESS | BFD_DECOMPRESS
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| BFD_COMPRESS_GABI | BFD_COMPRESS_ZSTD | BFD_CONVERT_ELF_COMMON
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| BFD_USE_ELF_STT_COMMON),
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| BFD_USE_ELF_STT_COMMON | BFD_NO_SECTION_HEADER),
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/* section_flags: mask of all section flags */
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(SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD | SEC_RELOC | SEC_READONLY
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@ -1099,7 +1099,7 @@ const bfd_target TARGET_LITTLE_SYM =
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(HAS_RELOC | EXEC_P | HAS_LINENO | HAS_DEBUG | HAS_SYMS | HAS_LOCALS
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| DYNAMIC | WP_TEXT | D_PAGED | BFD_COMPRESS | BFD_DECOMPRESS
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| BFD_COMPRESS_GABI | BFD_COMPRESS_ZSTD | BFD_CONVERT_ELF_COMMON
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| BFD_USE_ELF_STT_COMMON),
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| BFD_USE_ELF_STT_COMMON | BFD_NO_SECTION_HEADER),
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/* section_flags: mask of all section flags */
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(SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD | SEC_RELOC | SEC_READONLY
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@ -14,6 +14,9 @@
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sframe_get_funcdesc_with_addr API, change in the behavior of
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sframe_fre_get_ra_offset and sframe_fre_get_fp_offset APIs.
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* Add command-line option, --strip-section-headers, to objcopy and strip to
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remove ELF section header from ELF file.
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Changes in 2.40:
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* Objdump has a new command line option --show-all-symbols which will make it
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@ -1278,6 +1278,7 @@ objcopy [@option{-F} @var{bfdname}|@option{--target=}@var{bfdname}]
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[@option{-R} @var{sectionpattern}|@option{--remove-section=}@var{sectionpattern}]
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[@option{--keep-section=}@var{sectionpattern}]
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[@option{--remove-relocations=}@var{sectionpattern}]
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[@option{--strip-section-headers}]
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[@option{-p}|@option{--preserve-dates}]
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[@option{-D}|@option{--enable-deterministic-archives}]
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[@option{-U}|@option{--disable-deterministic-archives}]
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@ -1494,6 +1495,10 @@ will remove all relocations for sections matching the pattern
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'.text.*', but will not remove relocations for the section
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'.text.foo'.
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@item --strip-section-headers
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Strip section header This option is specific to ELF files.
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Implies @option{--strip-all} and @option{--merge-notes}.
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@item -S
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@itemx --strip-all
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Do not copy relocation and symbol information from the source file.
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@ -3484,6 +3489,7 @@ strip [@option{-F} @var{bfdname} |@option{--target=}@var{bfdname}]
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[@option{-R} @var{sectionname} |@option{--remove-section=}@var{sectionname}]
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[@option{--keep-section=}@var{sectionpattern}]
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[@option{--remove-relocations=}@var{sectionpattern}]
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[@option{--strip-section-headers}]
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[@option{-o} @var{file}] [@option{-p}|@option{--preserve-dates}]
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[@option{-D}|@option{--enable-deterministic-archives}]
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[@option{-U}|@option{--disable-deterministic-archives}]
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@ -3586,6 +3592,10 @@ will remove all relocations for sections matching the pattern
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'.text.*', but will not remove relocations for the section
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'.text.foo'.
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@item --strip-section-headers
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Strip section headers. This option is specific to ELF files. Implies
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@option{--strip-all} and @option{--merge-notes}.
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@item -s
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@itemx --strip-all
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Remove all symbols.
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@ -97,6 +97,7 @@ static int deterministic = -1; /* Enable deterministic archives. */
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static int status = 0; /* Exit status. */
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static bool merge_notes = false; /* Merge note sections. */
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static bool strip_section_headers = false;/* Strip section headers. */
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typedef struct merged_note_section
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{
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@ -365,6 +366,7 @@ enum command_line_switch
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OPTION_SREC_LEN,
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OPTION_STACK,
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OPTION_STRIP_DWO,
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OPTION_STRIP_SECTION_HEADERS,
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OPTION_STRIP_SYMBOLS,
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OPTION_STRIP_UNNEEDED,
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OPTION_STRIP_UNNEEDED_SYMBOL,
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@ -403,6 +405,7 @@ static struct option strip_options[] =
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{"preserve-dates", no_argument, 0, 'p'},
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{"remove-section", required_argument, 0, 'R'},
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{"remove-relocations", required_argument, 0, OPTION_REMOVE_RELOCS},
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{"strip-section-headers", no_argument, 0, OPTION_STRIP_SECTION_HEADERS},
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{"strip-all", no_argument, 0, 's'},
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{"strip-debug", no_argument, 0, 'S'},
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{"strip-dwo", no_argument, 0, OPTION_STRIP_DWO},
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@ -492,6 +495,7 @@ static struct option copy_options[] =
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{"remove-leading-char", no_argument, 0, OPTION_REMOVE_LEADING_CHAR},
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{"remove-section", required_argument, 0, 'R'},
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{"remove-relocations", required_argument, 0, OPTION_REMOVE_RELOCS},
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{"strip-section-headers", no_argument, 0, OPTION_STRIP_SECTION_HEADERS},
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{"rename-section", required_argument, 0, OPTION_RENAME_SECTION},
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{"reverse-bytes", required_argument, 0, OPTION_REVERSE_BYTES},
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{"section-alignment", required_argument, 0, OPTION_PE_SECTION_ALIGNMENT},
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@ -592,6 +596,7 @@ copy_usage (FILE *stream, int exit_status)
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--add-gnu-debuglink=<file> Add section .gnu_debuglink linking to <file>\n\
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-R --remove-section <name> Remove section <name> from the output\n\
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--remove-relocations <name> Remove relocations from section <name>\n\
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--strip-section-headers Strip section header from the output\n\
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-S --strip-all Remove all symbol and relocation information\n\
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-g --strip-debug Remove all debugging symbols & sections\n\
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--strip-dwo Remove all DWO sections\n\
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@ -730,6 +735,7 @@ strip_usage (FILE *stream, int exit_status)
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fprintf (stream, _("\
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-R --remove-section=<name> Also remove section <name> from the output\n\
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--remove-relocations <name> Remove relocations from section <name>\n\
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--strip-section-headers Strip section headers from the output\n\
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-s --strip-all Remove all symbol and relocation information\n\
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-g -S -d --strip-debug Remove all debugging symbols & sections\n\
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--strip-dwo Remove all DWO sections\n\
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@ -2695,7 +2701,16 @@ copy_object (bfd *ibfd, bfd *obfd, const bfd_arch_info_type *input_arch)
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necessary. */
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VerilogDataEndianness = ibfd->xvec->byteorder;
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if (bfd_get_flavour (ibfd) != bfd_target_elf_flavour)
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if (bfd_get_flavour (ibfd) == bfd_target_elf_flavour)
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{
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if (strip_section_headers)
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{
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ibfd->flags |= BFD_NO_SECTION_HEADER;
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strip_symbols = STRIP_ALL;
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merge_notes = true;
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}
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}
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else
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{
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if ((do_debug_sections & compress) != 0
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&& do_debug_sections != compress)
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@ -2712,6 +2727,13 @@ copy_object (bfd *ibfd, bfd *obfd, const bfd_arch_info_type *input_arch)
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bfd_get_archive_filename (ibfd));
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return false;
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}
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if (strip_section_headers)
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{
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non_fatal (_("--strip_section_headers is unsupported on `%s'"),
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bfd_get_archive_filename (ibfd));
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return false;
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}
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}
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if (verbose)
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@ -3456,7 +3478,7 @@ copy_object (bfd *ibfd, bfd *obfd, const bfd_arch_info_type *input_arch)
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free (merged);
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}
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}
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else if (merge_notes && ! is_strip)
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else if (merge_notes && ! is_strip && ! strip_section_headers)
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non_fatal (_("%s: Could not find any mergeable note sections"),
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bfd_get_filename (ibfd));
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@ -4759,6 +4781,9 @@ strip_main (int argc, char *argv[])
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case OPTION_REMOVE_RELOCS:
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handle_remove_relocations_option (optarg);
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break;
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case OPTION_STRIP_SECTION_HEADERS:
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strip_section_headers = true;
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break;
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case 's':
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strip_symbols = STRIP_ALL;
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break;
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@ -5228,6 +5253,10 @@ copy_main (int argc, char *argv[])
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handle_remove_relocations_option (optarg);
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break;
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case OPTION_STRIP_SECTION_HEADERS:
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strip_section_headers = true;
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break;
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case 'S':
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strip_symbols = STRIP_ALL;
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break;
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3
ld/NEWS
3
ld/NEWS
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@ -15,6 +15,9 @@
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* The linker script syntax has a new command for output sections: ASCIZ "string"
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This will insert a zero-terminated string at the current location.
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* Add command-line option, -z nosectionheader, to omit ELF section
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header.
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Changes in 2.40:
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* The linker has a new command line option to suppress the generation of any
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@ -807,6 +807,10 @@ fragment <<EOF
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"must be default, internal, hidden, or protected"),
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optarg);
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}
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else if (strcmp (optarg, "sectionheader") == 0)
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config.no_section_header = false;
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else if (strcmp (optarg, "nosectionheader") == 0)
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config.no_section_header = true;
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EOF
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if test x"$GENERATE_SHLIB_SCRIPT" = xyes; then
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3
ld/ld.h
3
ld/ld.h
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@ -280,6 +280,9 @@ typedef struct
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/* If set, code and non-code sections should never be in one segment. */
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bool separate_code;
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/* If set, generation of ELF section header should be suppressed. */
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bool no_section_header;
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/* The rpath separation character. Usually ':'. */
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char rpath_separator;
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@ -1544,6 +1544,11 @@ Don't create an ELF @code{PT_GNU_RELRO} segment if @samp{norelro}.
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Report dynamic relative relocations generated by linker. Supported for
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Linux/i386 and Linux/x86_64.
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@item sectionheader
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@itemx nosectionheader
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Generate section header. Don't generate section header if
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@samp{nosectionheader} is used. @option{sectionheader} is the default.
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@item separate-code
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@itemx noseparate-code
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Create separate code @code{PT_LOAD} segment header in the object. This
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@ -3434,6 +3434,10 @@ ldlang_open_output (lang_statement_union_type *statement)
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link_info.output_bfd->flags |= BFD_TRADITIONAL_FORMAT;
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else
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link_info.output_bfd->flags &= ~BFD_TRADITIONAL_FORMAT;
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if (config.no_section_header)
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link_info.output_bfd->flags |= BFD_NO_SECTION_HEADER;
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else
|
||||
link_info.output_bfd->flags &= ~BFD_NO_SECTION_HEADER;
|
||||
break;
|
||||
|
||||
case lang_target_statement_enum:
|
||||
|
|
|
|||
13
ld/lexsup.c
13
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
|
||||
|
|
|
|||
Loading…
Add table
Reference in a new issue