From 6a3bd2a059014310fb1030ee63d17388827dbe60 Mon Sep 17 00:00:00 2001 From: Kaylee Blake Date: Wed, 4 Mar 2020 19:18:07 +1030 Subject: [PATCH 1/6] 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, an new objcopy and strip option, --strip-sections, to remove ELF section header. bfd/ 2020-03-XX H.J. Lu Kaylee Blake 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/ 2020-03-XX H.J. Lu PR ld/25617 * NEWS: Mention --strip-sections for objcopy and strip. * doc/binutils.texi: Document --strip-sections for objcopy and strip. * objcopy.c (remove_section_header): New. (command_line_switch): Add OPTION_REMOVE_SECTION_HEADER. (strip_options): Add --strip-sections. (copy_options): Likewise. (copy_usage): Add --strip-sections. (strip_usage): Likewise. (copy_object): Handle --strip-sections for ELF files. (strip_main): Handle OPTION_REMOVE_SECTION_HEADER. (copy_main): Likewise. ld/ 2020-03-XX H.J. Lu Kaylee Blake 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. (elf_static_list_options): Add -z sectionheader and -z nosectionheader. --- bfd/bfd-in2.h | 8 ++++++-- bfd/bfd.c | 8 ++++++-- bfd/elfcode.h | 37 +++++++++++++++++++++++++++---------- bfd/elfxx-target.h | 6 ++++-- binutils/NEWS | 3 +++ binutils/doc/binutils.texi | 10 ++++++++++ binutils/objcopy.c | 35 +++++++++++++++++++++++++++++++++-- ld/NEWS | 3 +++ ld/emultempl/elf.em | 4 ++++ ld/ld.h | 3 +++ ld/ld.texi | 5 +++++ ld/ldlang.c | 4 ++++ ld/lexsup.c | 8 ++++++++ 13 files changed, 116 insertions(+), 18 deletions(-) diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h index 14e2e3b4819..043c5623a97 100644 --- a/bfd/bfd-in2.h +++ b/bfd/bfd-in2.h @@ -6593,17 +6593,21 @@ struct bfd /* Put pathnames into archives (non-POSIX). */ #define BFD_ARCHIVE_FULL_PATH 0x100000 + /* Don't generate ELF section header. */ +#define BFD_NO_SECTION_HEADER 0x200000 + /* Flags bits to be saved in bfd_preserve_save. */ #define BFD_FLAGS_SAVED \ (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_LINKER_CREATED \ | BFD_PLUGIN | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON \ - | BFD_USE_ELF_STT_COMMON) + | BFD_USE_ELF_STT_COMMON | BFD_NO_SECTION_HEADER) /* 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 100359ccfe6..32b598287f0 100644 --- a/bfd/bfd.c +++ b/bfd/bfd.c @@ -176,17 +176,21 @@ CODE_FRAGMENT . {* Put pathnames into archives (non-POSIX). *} .#define BFD_ARCHIVE_FULL_PATH 0x100000 . +. {* Don't generate ELF section header. *} +.#define BFD_NO_SECTION_HEADER 0x200000 +. . {* Flags bits to be saved in bfd_preserve_save. *} .#define BFD_FLAGS_SAVED \ . (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_LINKER_CREATED \ . | BFD_PLUGIN | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON \ -. | BFD_USE_ELF_STT_COMMON) +. | BFD_USE_ELF_STT_COMMON | BFD_NO_SECTION_HEADER) . . {* 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 68db3e9ee3d..0892215267d 100644 --- a/bfd/elfcode.h +++ b/bfd/elfcode.h @@ -266,6 +266,8 @@ elf_swap_ehdr_out (bfd *abfd, { unsigned int tmp; int signed_vma = get_elf_backend_data (abfd)->sign_extend_vma; + bfd_boolean 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 +278,10 @@ 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 +289,24 @@ 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 @@ -1040,6 +1054,9 @@ 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 1ae17f45ee2..8d25c84e800 100644 --- a/bfd/elfxx-target.h +++ b/bfd/elfxx-target.h @@ -970,7 +970,8 @@ const bfd_target TARGET_BIG_SYM = /* object_flags: mask of all file flags */ (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_CONVERT_ELF_COMMON | BFD_USE_ELF_STT_COMMON), + | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_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 @@ -1071,7 +1072,8 @@ const bfd_target TARGET_LITTLE_SYM = /* object_flags: mask of all file flags */ (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_CONVERT_ELF_COMMON | BFD_USE_ELF_STT_COMMON), + | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_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 1650a3ac934..a420ec117ab 100644 --- a/binutils/NEWS +++ b/binutils/NEWS @@ -1,5 +1,8 @@ -*- text -*- +* Add command-line option, --strip-sections, to objcopy and strip to + remove ELF section header from ELF file. + Changes in 2.34: * Binutils now supports debuginfod, an HTTP server for distributing diff --git a/binutils/doc/binutils.texi b/binutils/doc/binutils.texi index de3f1babb27..b3943e6a337 100644 --- a/binutils/doc/binutils.texi +++ b/binutils/doc/binutils.texi @@ -1186,6 +1186,7 @@ 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-sections}] [@option{-p}|@option{--preserve-dates}] [@option{-D}|@option{--enable-deterministic-archives}] [@option{-U}|@option{--disable-deterministic-archives}] @@ -1403,6 +1404,10 @@ will remove all relocations for sections matching the pattern '.text.*', but will not remove relocations for the section '.text.foo'. +@item --strip-sections +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. @@ -3262,6 +3267,7 @@ 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-sections}] [@option{-o} @var{file}] [@option{-p}|@option{--preserve-dates}] [@option{-D}|@option{--enable-deterministic-archives}] [@option{-U}|@option{--disable-deterministic-archives}] @@ -3363,6 +3369,10 @@ will remove all relocations for sections matching the pattern '.text.*', but will not remove relocations for the section '.text.foo'. +@item --strip-sections +Strip section header. 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 e6711a99fb2..89a80f7edeb 100644 --- a/binutils/objcopy.c +++ b/binutils/objcopy.c @@ -96,6 +96,9 @@ static bfd_boolean preserve_dates; /* Preserve input file timestamp. */ static int deterministic = -1; /* Enable deterministic archives. */ static int status = 0; /* Exit status. */ +/* Strip section header. */ +static bfd_boolean strip_sections = FALSE; + static bfd_boolean merge_notes = FALSE; /* Merge note sections. */ typedef struct merged_note_section @@ -352,6 +355,7 @@ enum command_line_switch OPTION_REDEFINE_SYMS, OPTION_REMOVE_LEADING_CHAR, OPTION_REMOVE_RELOCS, + OPTION_STRIP_SECTIONS, OPTION_RENAME_SECTION, OPTION_REVERSE_BYTES, OPTION_PE_SECTION_ALIGNMENT, @@ -399,6 +403,7 @@ 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-sections", no_argument, 0, OPTION_STRIP_SECTIONS}, {"strip-all", no_argument, 0, 's'}, {"strip-debug", no_argument, 0, 'S'}, {"strip-dwo", no_argument, 0, OPTION_STRIP_DWO}, @@ -487,6 +492,7 @@ 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-sections", no_argument, 0, OPTION_STRIP_SECTIONS}, {"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}, @@ -582,6 +588,7 @@ copy_usage (FILE *stream, int exit_status) --add-gnu-debuglink= Add section .gnu_debuglink linking to \n\ -R --remove-section Remove section from the output\n\ --remove-relocations Remove relocations from section \n\ + --strip-sections 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\ @@ -719,6 +726,7 @@ strip_usage (FILE *stream, int exit_status) fprintf (stream, _("\ -R --remove-section= Also remove section from the output\n\ --remove-relocations Remove relocations from section \n\ + --strip-sections Strip section header 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\ @@ -2621,7 +2629,16 @@ copy_object (bfd *ibfd, bfd *obfd, const bfd_arch_info_type *input_arch) return FALSE; } - if (bfd_get_flavour (ibfd) != bfd_target_elf_flavour) + if (bfd_get_flavour (ibfd) == bfd_target_elf_flavour) + { + if (strip_sections) + { + ibfd->flags |= BFD_NO_SECTION_HEADER; + strip_symbols = STRIP_ALL; + merge_notes = TRUE; + } + } + else { if ((do_debug_sections & compress) != 0 && do_debug_sections != compress) @@ -2637,6 +2654,13 @@ copy_object (bfd *ibfd, bfd *obfd, const bfd_arch_info_type *input_arch) bfd_get_archive_filename (ibfd)); return FALSE; } + + if (strip_sections) + { + non_fatal (_("--strip_sections is unsupported on `%s'"), + bfd_get_archive_filename (ibfd)); + return FALSE; + } } if (verbose) @@ -3360,7 +3384,7 @@ 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_sections) non_fatal (_("%s: Could not find any mergeable note sections"), bfd_get_filename (ibfd)); @@ -4670,6 +4694,9 @@ strip_main (int argc, char *argv[]) case OPTION_REMOVE_RELOCS: handle_remove_relocations_option (optarg); break; + case OPTION_STRIP_SECTIONS: + strip_sections = TRUE; + break; case 's': strip_symbols = STRIP_ALL; break; @@ -5101,6 +5128,10 @@ copy_main (int argc, char *argv[]) handle_remove_relocations_option (optarg); break; + case OPTION_STRIP_SECTIONS: + strip_sections = TRUE; + break; + case 'S': strip_symbols = STRIP_ALL; break; diff --git a/ld/NEWS b/ld/NEWS index 563af67a344..ee9a7c86198 100644 --- a/ld/NEWS +++ b/ld/NEWS @@ -1,5 +1,8 @@ -*- text -*- +* Add command-line option, -z nosectionheader, to omit ELF section + header. + * Add command-line options --enable-non-contiguous-regions and --enable-non-contiguous-regions-warnings. diff --git a/ld/emultempl/elf.em b/ld/emultempl/elf.em index bb7e5375303..1ce1af1236a 100644 --- a/ld/emultempl/elf.em +++ b/ld/emultempl/elf.em @@ -752,6 +752,10 @@ fragment <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 2597e2d6304..d3bc860a51a 100644 --- a/ld/lexsup.c +++ b/ld/lexsup.c @@ -1686,6 +1686,10 @@ parse_args (unsigned argc, char **argv) break; } + /* -z nosectionheader implies --strip-all. */ + if (config.no_section_header) + link_info.strip = strip_all; + if (!bfd_link_dll (&link_info)) { if (command_line.filter_shlib) @@ -1889,6 +1893,10 @@ elf_static_list_options (FILE *file) -z noexecstack Mark executable as not requiring executable stack\n")); fprintf (file, _("\ -z globalaudit Mark executable requiring global auditing\n")); + fprintf (file, _("\ + -z sectionheader Generate section header (default)\n")); + fprintf (file, _("\ + -z nosectionheader Do not generate section header\n")); } static void -- 2.25.1